Commercial fishery landings of the black scabbardfish, Aphanopus carbo, from the Madeira mid-water drifting longline fleet (northeastern Atlantic) were studied for 2 years within a Portuguese government programme for fishing management. The process noted that 20% of the total catch corresponded to the intermediate scabbardfish, Aphanopus intermedius. Length-frequency distribution, and age, growth and reproduction of both species were analysed and compared. The results revealed significant differences in age and growth in influencing the length-frequency distributions. Intermediate scabbardfish attained the largest size (148 cm TL) and age (15 years). However, the two species had similar reproductive strategies. According to data published on A. carbo in this region, it is thought to be very likely that previous studies unintentionally mixed both species together in their analyses.

The structure and temporal variations of the fish community in the intertidal estuarine zone of shallow mud areas have been poorly studied in China. This paper analyses the diel, semi-lunar and seasonal patterns of fish assemblages in the Yangtze estuary in 2006. Fish were collected by consecutive day and night samplings using tide-stow-nets deployed parallel to each other in three stations. A total of 56 fish species belonging to 21 families was caught during the study period. The family Cyprinidae dominated with 25 species. Freshwater fish species were the important dominant commercial fishery species and well represented with five species (sharpbelly Hemiculter bleekeri, goldfish Carassius auratus, bream Parabramis pekinensis, likely-bream Pseudobrama simony, and glossy yellow catfish Pelteobagrus nitidus) in the three stations. Juvenile fishes dominated the fish community, comprising 93.9% in station 1 and 96.6% in station 2 of the total abundance. The number of fish species in day tides was slightly lower than those in night tides in spring and summer, but the opposite in other seasons. In neap tides, the numbers and abundance of fish species were both lower than those in the spring tides. Fish abundance was lowest in winter, increasing during spring and summer (March–September) in both stations 1 and 2, with obviously large fluctuations in each season. The pattern of habitat selection of fishes could effectively decrease the food competition of intraspecies or interspecies and favour the growth and nursing of young fishes. These findings indicate that the intertidal zones in the estuary may serve as important nursery areas for fish communities.

The effects of thermal stress on survival, development and heat shock protein (hsp) expression of green sturgeon (GS) yolk-sac larvae, from hatching through yolk depletion were investigated to provide insight into effects of highly altered natural river hydrographs. Hatched GS larvae were reared at constant water temperatures 18°C (control) through 28°C at 2°C increments. Larval survival significantly decreased at 26–28°C, with 28°C being lethal. Significant proportions of deformed larvae were found at sub-lethal (20–26°C) and lethal 28°C rearing temperatures, with kyphosis (i.e. backward flexion of notochord) accounting for >99% of morphological deformities. Histological analysis of larvae preparations indicate that elevated water temperature affects notochord cell function and physiology. At rearing temperatures 20–28°C, thermal stress elicited a quick (24 h) and long lasting (yolk-sac absorption) significant over-expression of measured heat shock proteins (hsps), all of which are known components of intracellular protein repair and stabilization mechanism. Thermal sensitivity, as indicated by the incidence of abnormalities and expression of different hsps, varied significantly between crosses. Thermally tolerant progeny exhibited a short but rapid hsp72 (size in kDa) over-expression, and more pronounced hsp60 and hsp90 over-expression, than less tolerant progeny which exhibited a prolonged hsp72 and hsp78 over-expression. At environmentally relevant water temperatures bent larvae exhibited spiral swimming, which in the wild would compromise the ability of emerging larvae to forage, avoid predators, and migrate downstream, ultimately compromising survival and recruitment. Before larvae hsp content can be used as a thermal-stress biomarker for GS, field validation studies are needed.

Weight–length relationships are presented for 12 fish species from a subsystem of the Río de la Plata estuary in Uruguay. This study provides new maximum lengths for three species and a new reference for the weight–length relationship of one species.

Oilfish, escolar, snake mackerel (order Aulopiformes, family Gempylidae), and longnose lancetfish (order Perciformes, family Alepisauridae) sampled from the western North Atlantic and the Gulf of Mexico were analyzed for length–weight and length–length relationships. These species are encountered as occasional bycatch of pelagic longline fisheries. The fish (161 specimens, 19.0–149.1 cm TL) were collected over a 3-year period (January 2007–January 2010) from pelagic longline gear targeting swordfish and tuna. For each species, 95% confidence limits (CI) of parameters b and log a and regression coefficients (r²) were calculated for log-transformed length–weight relationships. The length–weight parameter b for all species ranged from 2.881 to 3.358, with regression coefficients (r²) ranging from 0.75 to 0.98. Linear relationships between fork lengths, standard lengths, and total lengths were also calculated.

Presented are the length-weight relationships for eight shark species (Families Carcharhinidae and Sphyrnidae) caught by the small-scale fishery in southeastern Brazil, from July 1996 to December 2003.

The effect of two environmental factors (substrate type and water velocity regime) was studied in the ontogenetic migration intensity of kaluga, Huso dauricus, a protected species in the Amur River. Early-life stages studied were: free embryos = days 0–8; larvae = days 9–49; and juveniles = days 50–66. Effect of treatments on fish migration intensity was observed in circular channels, allowing migration in an endless stream. Daily migration intensity of fish was characterized by counting the number of daily upstream or downstream fish passes past a specific site in the channel observed for 5 min every hour by vision or video camera. The hypothesis that substrate type (bare bottom or sand-small cobble) affects migration intensity was accepted, depending on the life stage. For example, the substrate type had no effect on migration intensity of days 0–6 free embryos. However, the intensity in days 7–8 free embryos and days 9–29 larvae was greater over rock substrate, while intensity in days 46–49 larvae and days 50–66 juveniles was greater when the bottom was bare. Thus, the effect of the substrate on migration varied in intensity according to the life stage, and within the larva life stage, by age. The velocity regime had a positive effect on migration intensity of free embryos, but a high velocity (mean, 29.9 cm∙s⁻¹) delayed the resting period of day 8 free embryos and day 9–15 larvae. Free embryos and larvae in low vs fast velocities showed that they may have a drive to migrate a similar distance, and moreover, that a triggering velocity may be needed to initiate or to stop migration. The hypothesis was accepted that the rearing velocity affects migration intensity, e.g. larvae reared in still water and then placed in moving water had a compensatory migration intensity response. For population enhancement stocking of H. dauricus, the results indicate culture practices must insure that: (i) same-population individuals are mated to produce early-life stages with the correct behaviour, (ii) migrating larvae, not juveniles, should be stocked, and (iii) larvae should be released in a river reach with a bottom velocity ≥30 cm∙s⁻¹ containing sand and small pebbles.

Hook selectivity, sex ratio of catches and relative abundance (Catch Per Unit Effort – CPUE) were assessed for the pelagic stingray Pteroplatytrygon violacea (Bonaparte, 1872), caught by longline gear in the southwestern Atlantic Ocean over the continental slope and adjacent oceanic area. The catches were carried out at depths of 200–4000 m by research cruises in 2002 and 2003, from Cabo Frio (22°52′S) to Laguna (28°28′S); and by hook selectivity experiments from 2004 to 2008, from Itajaí (26°54′S) to Tramandaí (29°59′S). Hook selectivity experiments indicated higher catches of stingrays with ‘J’ hooks (9/0, 10° offset) commonly used by the pelagic longline fleet than with ‘circle’ hooks (18/0, 10° offset). ‘circle’ hooks reduce the longline by-catches of this species. Most of the stingrays caught were males (6 : 1). One female aborted mid-term embryos at the time of capture. CPUE was highest between spring and autumn and lowest during winter.

The present study describes length-weight relationships (LWRs) of three species of the family Rivulidae, Austrolebias nigrofasciatus, Austrolebias wolterstorffi and Cynopoecilus melanotaenia, captured in temporary freshwater wetlands of southern Rio Grande do Sul, Brazil from May to December 2011. The growth pattern for both species was predicted using a linear regression of LWR. Estimates of parameter b ranged from 2.81 in male C. melanotaenia to 3.34 for females A. nigrofasciatus. The present observations are significant for conservation and management because these species are threatened and their habitats are under pressure.

Ages were estimated from otoliths, opercular bones, scales, and vertebrae of 514 specimens of Channa punctata from three Indian rivers – the Ganga, Gomti, and Yamuna – to evaluate the potential bias of age estimates between readers and between pairs of aging structures. Standard procedures were followed to prepare and study the age structures. Among all structures, otoliths showed highest (97.4%) values of agreement between readers' age estimates followed by the opercular bones (89.5%), scales (84.2%) and vertebrae (78.9%). Because of the highest percentage of agreement and lowest average percentage of error (0.05%) and coefficient of variation (0.76%) values between readers, otoliths were considered the most suitable aging structure for C. punctata. When otoliths ages were compared with those of the other structures viz., opercular bones, scales and vertebrae, percentage of agreement was found highest between estimates (90.8%) of otoliths and opercular bones.

The current study was undertaken in order to assess the risk that different ranaviruses might impose on European sheatfish aquaculture. As the European sheatfish virus (ESV) is a known pathogen causing losses in European sheatfish aquaculture, it was assumed that closely related exotic ranaviruses might also be able to infect European sheatfish and probably cause disease and mortality in this species. The differential susceptibility of European sheatfish (Silurus glanis) to various ranavirus isolates was assessed at two different temperatures (15°C and 25°C) in a recirculation system. Fish were infected experimentally with a panel of ranavirus isolates including ESV, European catfish virus (ECV), European catfish virus isolate 24 (ECV-24), Epizootic haematopoietic necrosis virus (EHNV), Rana esculenta virus isolate Italy 282/ I02 (REV), short-finned eel virus (SERV), Bohle iridovirus (BIV), guppy virus 6 (GV6), doctor fish virus (DFV) and Frog virus 3 (FV3). Significant mortalities were observed, as expected, in fish infected with ESV at 15°C (100%) as well as at 25°C (86/83%). Fish infected with ECV at 15°C showed no clinical signs of disease (8% mortality), whereas those fish infected at 25°C exhibited a cumulative mortality of 54%. Fatal disease was also induced by Italian isolate ECV-24 at 25°C (81%). Virus isolates ESV, ECV and ECV-24, generally the most genetically closely related viruses, were successfully isolated from dead fish by cell culture with subsequent identification by polymerase chain reaction (PCR) and sequence analysis. However, no mortality or clinical signs of disease were observed in the groups of sheatfish infected with the other ranaviruses investigated in the study, and none of those viruses were re-isolated in cell culture or identified by PCR. It was concluded that European sheatfish are susceptible to infection with ESV, ECV and ECV-24 under laboratory conditions, but not to infection with EHNV, REV, SERV, BIV, GV6, DFV or FV3. For ESV, the incubation period was shorter at 25°C compared to 15°C water temperature, but whereas all fish died after ESV infection at 15°C, some fish survived the infection at 25°C. Futhermore, the very young sheatfish were susceptible to ECV and ECV-24 at 25°C, whereas there was no significant mortality in the group of older sheatfish challenged with ECV at 15°C. Therefore, the clinical characteristics of the disease seem to depend on the age of the fish as well as on the water temperature.

Little is known about the functional consequences of triploidy in Atlantic cod. This study compared the gut morphology of diploid and triploid offspring of wild and selected broodstock. Three-year-old triploid offspring of wild cod (mean weight 1695 ± 346 g) had approximately 18% fewer pyloric caeca (125 ± 9 vs 172 ± 14, P < 0.001) and a 23% shorter intestine [Relative Gut Length, (RGL); 1.40 ± 0.17 vs 1.81 ± 0.17, P < 0.05] than their diploid siblings (mean weight: 1820 ± 262 g). Two-year-old triploid offspring of selected broodstock (mean weight: 640 ± 64 g) had 20% fewer pyloric caeca (309 ± 17 vs 387 ± 27, P < 0.001) but similar RGL to their diploid siblings (mean weight: 820 ± 69 g). The average number of mucus cells in the columnar epithelium of pyloric caeca was significantly higher in triploid than in diploid cod (54 ± 9 vs 25 ± 5, P < 0.001). There was no correlation between pyloric caeca number and RGL, or between mucus cells and pyloric caeca number, and no significant differences between sexes for any of the measured variables. Overall, the observations highlight some differences in the digestive system of these two ploidy groups that could have an influence on nutrient utilization and performance capacity in triploids compared to diploids.

The purpose of this study was to determine critical components of the life history including otolith age validation, growth estimation, and reproductive characteristics for southern kingfish Menticirrhus americanus. A total of 2233 southern kingfish were collected from March 2009 to December 2010. Ages were estimated and validated using thin-sectioned otoliths. Marginal increment analysis showed a single annulus was deposited once a year between April and May. Growth was significantly different (P < 0.0001) between sexes L_inf = 418.97 ± 16.58 mm, k = 0.29 ± 0.03, t₀ = −1.30 ± 0.10 for females and L_inf = 290.74 ± 6.93 mm, k = 0.52 ± 0.05, t₀ = −1.08 ± 0.11 for males. Southern kingfish spawn from March to August with a peak spawn in April. Based on evidence of multiple oocyte maturation stages and post-ovulatory follicles (POFs) southern kingfish are multiple spawners exhibiting indeterminate fecundity. Spawning frequency for females ranging from 222 to 351 mm TL (age 1–5) was estimated as one spawning event every 2.0–4.2 days with up to 6 million total ova produced per spawning season per female.

Anglers' records of fish weight (ARFW) were analysed in Poland for the periods 1965–1989 (successive increases in inland water pollution), and 1990–2010 (considerable improvements in water quality). For the initial ARFW analysis, the entire study was divided into nine intervals of 5 years each; the period that followed was divided into three catchments: the Vistula, Oder and Pomeranian rivers, whereby 10 species were chosen to represent obligatory riverine and facultative species. With a few exceptions, the investigated species showed unexpected and varying reactions to the changes in water quality. The ARFW of obligatory riverine barbel Barbus barbus (L.) decreased during the first periods (1965–1989), then increased significantly from 1990 to 2010. For obligatory riverine ide Leuciscus idus (L.), tendencies were less clear but as significant. However, other obligatory riverine species have not shown a relationship between ARFW and water quality. Discrepancies were also recorded in the facultative riverine pike (Esox lucius L.) and brown trout (Salmo trutta L.). Considering the number of medals recorded, there were some interesting tendencies related to the decline or improvement in the water quality, although not in all investigated species. The species displaying a decrease in medals awarded from 1966 to 1989 and increasing after 1990, was chub Leuciscus cephalus (L.), but only until 2005. Species which showed successive increases in awards from 1989 to 2010 were: pike, perch (Perca fluviatilis L.), ide, and wels (Silurus glanis L.). However, for species in the period when the water quality actually deteriorated (1966–1990), the number of medals awarded increased: barbel, brown trout (S. trutta L.), and grayling Thymallus thymallus (L.).

The ages and growth of longnose trevally (Carangoides chrysophrys), caught in the northwest Arabian Sea between April 2005 and September 2006, were investigated. Age and growth of 336 fish specimens were determined using sectioned sagittae otoliths. Annual opaque growth rings were formed between December and March, with the majority being laid down in February and March, coinciding with the spawning period and high water temperatures. Marginal zone or edge analysis was used to validate the annual deposition of the opaque zone in the otoliths. This species showed large variations in length-at-age, suggesting large growth variations among individuals of the same cohort. The estimated von Bertalanffy growth model differed significantly between the sexes, with males having larger mean lengths at age and reaching a larger asymptotic size. The von Bertalanffy growth models were TL (cm) = 73.34[1-exp (−0.25 (t + 1.21))] and TL(cm) = 73.26[1-exp (−0.24 (t + 1.20))] for males and females, respectively.

The purpose of the present study was to analyze the diet of the smooth butterfly ray Gymnura micrura using qualitative and quantitative approaches to describe the feeding spectrum as well as ecological aspects related to feeding and niche width. The rays were obtained through monthly sampling as by-catch from bottom trawl fisheries in northeastern Brazil from August 2007 to July 2008. A total of 286 stomachs were sampled, of which 176 contained food items. G. micrura is a predator in the region that feeds intermittently on large whole prey items, followed by a long period of digestion with simply little or no feeding activity. A low diversity of food items was found in the G. micrura diet, with an absolute predominance of teleosts, especially the roughneck grunt Pomadasys corvinaeformis. It is suggested that the species has a narrow feeding niche and a high degree of specialization. This presumed high degree of feeding specialization is discussed and the findings are compared in light of similar studies for closely related species, allowing to propose the family as primarily constituting piscivorous rays.

Length–weight relationships (LWR) are presented for five commercial freshwater fish species (Luciobarbus esocinus, Heckel, 1843; Capoeta trutta, Heckel, 1843; Barbus lacerta, Heckel, 1843; Luciobarbus mystaceus, Pallas, 1814 and Capoeta umbla, Heckel, 1843) collected from Keban Dam Lake located in eastern Anatolia, Turkey. Studied samples were obtained between July and December 2008 using commercial gill nets. For each species the sample size, length range, weight range, length-weight relationships, 95% confidence intervals of a and b, coefficient of correlation and growth type are given. Values of b were between 2.915 (Luciobarbus esocinus) and 3.079 (Copoeta trutta) and r² values from 0.919 (Copoeta trutta) to 0.987 (Barbus lacerta) in the study. New maximum length and length–weight relationships are reported for Barbus lacerta and Luciobarbus mystaceus.

Specimens of 43 fish species belonging to 25 families were collected from seasonal bottom trawl surveys in Haizhou Bay from March to December 2011. The length–weight relationships (LWRs) of these fish species were estimated, with 22 species presented for the first time. Maximum total length records of ten species exceeded those in FishBase. The effects of sex, season and growth phase on the relationships for some of these species were taken into account whereby one species had significantly (P < 0.05) different LWRs by sex, and eight species exhibited significantly different LWRs by season. Two different growth stanzas were detected for two species using the double-logarithmic plot of body weight versus total length.

Genome duplications and polyploidization events are thought to have played relevant roles in the early stages of vertebrate evolution, in particular near the time of divergence of the lamprey lineage. Additional genome duplications, specifically in ray-finned fish, may have occurred before the divergence of the teleosts. The role of polyploidization in vertebrate genome evolution is a thriving area of research. Sturgeons (order Acipenseriformes) provide a unique model for the investigation of genome duplication, with existing species possessing 120, 250 or 360 chromosomes. In the present study, data from 240 sturgeon specimens representing 11 species were used for analysis of ploidy levels. Allele numbers were assessed at eleven microsatellite loci. The results provide further evidence for functional diploidy, tetraploidy and hexaploidy in species possessing 120, 250 and 360 chromosomes, respectively. The analysis also uncovered novel evidence for functional hexaploidy in the shortnose sturgeon (Acipenser brevirostrum). In conclusion, the process of functional genome reduction is demonstrated to be an on-going process in this fish lineage.

Length–weight relationships (LWR) of fishes are necessary for various purposes such as stock/ecological assessment, monitoring and management (Froese, 2006). In this study we report length–weight relationships for five species of stingrays found in the Persian Gulf, Iran. Only one LWR was previously reported in the scientific literature for Rhinoptera javanica (Raje, 2000).

To determine the selectivity of gillnets in the Chilean artisanal fishery for the Chilean hake Merluccius gayi gayi, an experimental net was used with three mesh sizes (5.2, 6.8 and 7.6 cm). A total of 2279 specimens of Chilean hake were caught (24–56 cm total length, TL), mainly via gilling and snagging. The catch proportion below the size of sexual maturity SSM_50% (37 cm TL) for each mesh size tested was estimated. Models were fitted separately according to the sex to compensate for differences in size compositions, with the males fitted to a binormal model and females fitted to the normal location model. Analysing both sexes combined, the model with the lowest deviance was lognormal, with estimated modal lengths of 30.9, 40.2 and 43.9 cm TL for meshes of 5.2, 6.8 and 7.6 cm, respectively. The estimated selectivity factor (SF) indicates that the modal size matches the SSM_50% with a mesh size of 6.2 cm, while the length of retention of 50% (l₅₀) coincides with the SSM_50% with a mesh size of 7.6 cm.

An experiment was carried out to investigate the effects of short-term fasting periods on the serum biochemical characteristics of rainbow trout, Oncorhynchus mykiss. For this purpose, fish were fasted 0, 6, 12, 24, 48 and 72 h before blood sampling. Thereafter the serum levels of thyroxine (T₄), 3,5,3′-triiodothyronine (T₃), cortisol, glucose, lactate, triglyceride, cholesterol, total protein, albumin, globulin and albumin : globulin ration (A : G) were determined. Results show that serum levels of T₄ (4.60–8.77 ng ml⁻¹), T₃ (7.50–13.3 ng ml⁻¹), cortisol (7.91–24.5 ng ml⁻¹), glucose (18.5–80.1 mg dl⁻¹), lactate (12.7–29.6 mg dl⁻¹), triglyceride (171–500 mg dl⁻¹), and cholesterol (321–535 mg dl⁻¹) were significantly affected by the fasting period. However, there were no significant changes in serum total protein (3.03–3.68 g dl⁻¹), albumin (1.78–2.01 g dl⁻¹), globulin (1.15–1.70 g dl⁻¹) or A : G (1.13–1.93) among the fish fasted 0–72 h. Results clearly show the importance of a fasting period on the serum biochemical properties of rainbow trout. According to the results, 24 h fasting is suggested as a pre-sampling fasting period in rainbow trout to measure serum levels of T₄, T₃, cortisol, glucose, lactate, triglyceride, and cholesterol. Potential mechanisms related to the changes in biochemical properties are discussed.

The present study investigates carcass traits of farmed freshwater Catla catla for important information in calculating yield and/or providing data for programming machine/manual handling. For this purpose specimens of C. catla ranging from 1880 to 2150 g were collected from grow-out culture ponds of the Central Institute of Freshwater Aquaculture, Odisha State, India. Carcass yield, offal yield and carcass cutability were assessed. The percentage of head yield was highest (31.2%) in comparison to other carp species. Gutted yield and final dressed yield of 2 kg market class catla amounted to 85.4 and 54.1%, respectively. The average meat : bone ratio in filleting was reported to be 3 : 9. The middle cut of catla had both the highest total yield percentage and highest meat yield. Dry matter, ether extract and protein percentage was highest in the fore cut followed by the middle and hind cuts.

To determine if anthropogenically modified habitats possess greater numbers of round goby and serve as dispersal vectors, we used angling to compare catch-per-unit of effort for 64 natural and modified habitat areas. In addition, a gravel natural habitat was seined to compare length frequency distribution with anthropogenically modified habitats. Natural habitats included gravel beaches and natural rubble and cliff wall, while modified habitats included artificial riprap, concrete sea wall, and metal sheet piling. No significant difference in relative abundance was observed in round goby preference among modified habitats (P = 0.52), but natural gravel habitats were significantly different from modified habitats that included artificial riprap (P = 0.002), concrete sea wall (P < 0.001), and metal sheet piling (P = 0.003). When habitat subcategories were compared using anova, the natural gravel beach habitat was significantly different from the three artificial substrates and from natural rubble and cliff wall substrates (P < 0.004). No round goby were caught from gravel beach habitats; thus, this habitat was removed from further analysis. A Student t-test indicated no significant difference between habitats was found between the natural rubble and cliff wall habitat and the three other artificial habitats (concrete sea wall, P = 0.33; riprap, P = 0.53; metal sheet piling, P = 0.11). We further evaluated gravel beach habitats to determine the reason for the lack of goby capture. We seined gravel beach habitat and collected 328 individuals, with which we evaluated the length-frequency distribution and calculated length–weight relationships by sex. Our results indicated that only 5.2% of the goby population was available for capture by angling on the gravel beach habitat. A t-test comparing the demographic attributes between seining and angling indicated a significant difference between goby length (P < 0.001) and weight (P < 0.001). The regression slope indicated an ontogenetic habitat shift occurred near 62 mm standard length. Smaller round goby individuals were found in less structurally complex gravel beach habitat, while larger individuals were associated with complex habitat.

The anadromous sea lamprey (Petromyzon marinus) stop feeding during spawning migration; following the migration effort, the energy reserves of their tissues are expected to be mobilised and depleted. The present work aimed at testing if mobilisation of nutrients occurred in sea lampreys during the 2011 spawning run in the Minho River. Professional fishermen at three sampling sites captured the individuals used: two at the beginning of the freshwater spawning migration (one at the river mouth and one upstream the estuary) and one near the spawning grounds (35 km upstream the estuary limit). The total lipids (Folch extraction), protein (nitrogen conversion), energy content (direct calorimetry) and fatty acids (GC/EI-MS-SIM) were determined in the carcass (n = 19) and female liver (n = 8) and gonads (n = 8). The results indicated that a reduction of carcass dry matter during migration was mainly caused by a lipid decrease (51.0 ± 2.46% downstream and 38.0 ± 2.92% upstream, LSmean ± SE). In females, a decrease in the measured amounts of liver lipids was also observed (4.28 ± 2.637 g downstream and 0.64 ± 2.206 g upstream, LSmean ± SE) and the monounsaturated fatty acids consistently composed the larger fraction of lipids in all tissues (ranging between 42.9 ± 4.20% and 54.9 ± 3.43% of total fatty acids, LSMean ± SE). The results suggest a dynamic nutrient mobilisation and the major importance of liver fatty acids (such as 14:1n-5 and 16:1n-7) as possible energy sources for embryonic development or combustion during spawning migration. The P. marinus individuals captured at the intermediate sampling site (approximately 35 km upstream river mouth) in the middle of the season seemed as ready to spawn as the upstream sea lampreys.

Identification of ichthyoplankton is difficult because fish during early life stages often lack stable morphological characteristics; such difficulty in species identification can be a major hindrance in conducting ichthyoplankton surveys for fish biodiversity investigations. Here, we evaluated the feasibility of a molecular operational taxonomic unit (MOTU) approach for ichthyoplankton investigations, and describe fish biodiversity in the Jinshajiang section of the upper Yangtze River, China. The MOTUs were established by grouping specimens diverging less than 1.00% Kimura two-parameter (K2P) distance units from their nearest neighbor within the same MOTU, based on previous work on between-species divergences of the mitochondrial cytochrome C oxidase subunit I (COI) gene. Taxonomic assignment of the MOTUs was performed by comparing the MOTU sequences with the COI sequences of taxonomic species. Sixty-eight MOTUs were inferred from 818 COI sequences of ichthyoplankton in the Jinshajiang river section. Among those, one MOTU was composed of two identified taxonomic species, and each of the other MOTUs was linked to a single, identified taxonomic species. Only 26 MOTUs were successfully identified to taxonomic species due to the limited reference database. Our results demonstrate that the MOTU approach can be applied successfully for analyzing biodiversity and identifying species of freshwater ichthyoplankton. Compared with previous ichthyoplankton investigations the richness of ichthyoplankton was very high. High diversity of ichthyoplankton noted in our study suggests that the Jinshajiang section should be an important target for fish biodiversity conservation in the Yangtze River.

Accurate age estimation is important for stock assessment and management. The importance of reliable ageing is emphasized by the impending analytical assessment of whiting (Merlangius merlangus) in the Baltic Sea. Whiting is a top predator in the western Baltic Sea, where it is fished commercially although less extensively compared to the North Sea. Although the species is considered one of the most difficult gadoids to age, few efforts have been made to shed light on the ageing problems. The aim of the present study was to identify and validate the 1st winter ring and to examine the visibility of the subsequent winter rings. Microstructure analysis was used to confirm the 1st winter ring. Additionally, otolith growth trajectories were obtained, confirming the allometric growth as seen in many fish species. The method for ageing of whole otoliths presented in this study can be directly implemented in future ageing of whiting otoliths from the Baltic Sea – and potentially also adjacent areas where the conspecifics have similar growth rates.

Population characteristics of pallid sturgeon Scaphirhynchus albus in the lower Missouri River are relatively unknown. Therefore, data collected from the Nebraska Game and Parks Commission Pallid Sturgeon Population Assessment Program was synthesized to (i) document the population structure of pallid sturgeon by origin (hatchery-reared or wild), gender, and reproductive readiness, (ii) document the minimum size and age-at-maturity by gender, and (iii) document the fecundity rates of the fish that were successfully spawned in the hatchery. During this 4-year study (2008–2011), relative abundance for wild and hatchery-reared pallid sturgeon collected with gill nets did not significantly change whereas relative abundance for wild fish using trot lines declined significantly. The proportion of hatchery-reared pallid sturgeon increased annually, with the population being composed primarily of hatchery-reared fish. The proportion of reproductively ready females to non-reproductively ready females was 1 : 2.0, compared to male ratios at 1 : 0.9. Minimum fork length-at-maturity was estimated for females at 788 mm and for males at 798 mm. Minimum age-at-maturity for hatchery-reared released fish was age-9 for females and age-7 for males. Highest relative fecundity, based on the ovosomatic index, was 10% with an overall mean of 7%. The number of eggs per ml (egg size) was not correlated with fork length (P = 0.0615) or weight (P = 0.0957). Relative condition factor (Kn) for females was significantly different by reproductive condition (P = 0.0014) and Kn for males did not differ between reproductive conditions (P = 0.2634). Detecting shifts in population characteristics are essential not only to understand population dynamics since hatchery inputs and natural perturbations continue to change the population structure but also to assess species recovery efforts to ensure long-term species sustainability.

Sagittal otoliths, dorsal spines and scales were critically assessed as structures to potentially determine the age of the long-finned gurnard, Lepidotrigla argus. Counts were made of opaque growth increments and a readability score was assigned to each structure. Comparisons of growth increment counts were made between structures and between readings. All three structures showed some degree of readability and quantifiable growth increments, but this varied within fishes and between structures. Initial results showed that whole otoliths were more suitable to determine age estimates than dorsal spines and scales. Scales were considered unsuitable due to between reading ageing bias, variation in age estimates between structures, low precision and poor readability for this species. Dorsal spines showed evidence of loss of growth increments due to hollowing of the vascular core, which resulted in underestimation of older individuals in comparison to whole otoliths. Further analysis showed that growth increment counts from whole otoliths were lower for older individuals in comparison to sectioned otoliths. It is suggested that this is because of decreased clarity of growth increments towards the outer margin of whole otoliths in older individuals; this problem was not present with sectioned otoliths. It was concluded that sectioned otoliths were a more suitable structure from which to estimate age of L. argus than were whole otoliths, dorsal spines and/or scales.

This study was conducted to investigate the differences in the proximate composition (moisture, fat, protein and ash), cholesterol content, energy, mineral composition (Na, Ca, Mg, K, P, Fe and Zn) and fatty acid profile of rainbow trout, Oncorhynchus mykiss, after frying, boiling, or microwaving. Results showed that all cooking methods reduced moisture and increased total protein, fat and ash contents. Also all minerals increased significantly during the microwave and frying methods. Statistical results showed that the major fatty acids among the saturated and monounsaturated fatty acids in each fish were palmitic (C16:0) and oleic (C18:1) acids, respectively. In addition, linoleic acid (C18:2) was predominant in the n-6 polyunsaturated fatty acids (PUFA) in both cooked and raw trout. The EPA (eicosapentaenoic acid; C20:5 ω3) and DHA (docosahexaenoic acid; C22:6 ω6) acids were the major fatty acids among total n-3 acids in fish samples. The fatty acids profile of the cooked fish showed a saturated (SFA) and monounsaturated (MUFA) decrease and an increase in PUFA contents. However, the ω-3 fatty acids content increased in microwaved samples but decreased in the fried samples. Moreover, the PUFA/SFA and Hypocholesterolaemic/Hypercholesterolaemic (HH) ratios increased in both fried and microwaved trout, whereas significant increases in ω3/ω6 as well as EPA + DHA/C16 content were observed only in microwaved samples. A significant increase in energy content was observed in all cooked samples, whereas the cholesterol decreased. Research results show that microwaving is recommended as the best cooking method for a healthy consumption of rainbow trout.

A study was conducted to ascertain the genetic structure and the level of heterozygosity of Acipenser persicus in the Caspian Sea. A total of 167 fish were randomly collected from Turkmenistan, Russia and two regions of Iran. The number of alleles of eleven microsatellite markers ranged from 3 to 21 and the mean observed values of heterozygosity were 0.56 ± 0.20, 0.64 ± 0.14, 0.67 ± 0.16, and 0.64 ± 0.11. The observed heterozygosity was lower than the expected levels. The observed low genetic differentiation indicates that all populations are closely related. Hence, inbreeding is a potential problem, which should be taken into consideration in future breeding programs to avoid a further decline in genetic diversity.

It is hypothesized that Capoeta antalyensis (Battalgil, 1943) and Pseudophoxinus antalyae (Bogutskaya, 1992) might display specific growth characteristics that differ from other species of their genus. Age and growth were described for species from Duden Creek (Antalya, Turkey) from February 2008 to January 2009. The length–weight relationship for all individuals were described by the parameters: a = 0.0143 and b = 2.946 for C. antalyensis and a = 0.0084 and b = 3.251 for P. antalyae. The von Bertalanffy growth parameters based on data from scales were L∞ = 35.78 cm, k = 0.251 year⁻¹ and t₀ = −0.30 for C. antalyensis and L∞ = 22.59 cm, k = 0.232 year⁻¹ and t₀ = −0.78 for P. antalyae. The growth characteristics for these two species are not much different from those of closely related species from the same genus.

Ovaries of 1159 Trachinocephalus myops were examined, and six oocyte stages were histologically identified whereby each stage of ovary development was observed almost every month. The sex ratio was not different from 1 : 1 (P > 0.01). The weight-length relationship was estimated as BW = 0.0077FL^3.1207 (r² = 0.976, n = 2256). Monthly composition of the oocyte stages gonadosomatic index (GSI), and condition factor (CF) were examined. The spawning season had two peaks: February to April and August to October. Sizes at 50% maturity were estimated at 18.0 and 18.7 cm FL for females and males, respectively. Fecundity estimates ranged from 11 100 to 426 200 (mean: 178 600), based on an oocyte diameter >0.2 mm. Batch fecundity was estimated to range from 1724 to 120 951 (mean: 60 200), germinal vesicle migration and mature oocytes >0.8 mm in diameter were counted, and the relative fecundity was estimated to range from 346 to 3115 (mean: 1087). The results suggest that reproductive activity occurred throughout the year, suitable for the highly variable environments utilized by this species.

The aim of this study was to test young-of-the-year (YOY) assemblage applicability for the ecological quality assessment on the basis of samples from 55 sites scattered across the entire Czech Republic. European Fish Index (EFI) values estimated with YOY and adults were positively correlated, indicating that YOY and adult sampling is comparable. YOY bias the EFI toward significantly lower values, however, adults also lead to underestimated EFI values on some occasions. Relative differences between EFI YOY and EFI adults show almost normal distributions and indicate that there is no detectable systematic bias caused by environmental conditions or intensity of sampling. As shown in the Elbe River example, the reason for lower EFI YOY values could be found in a longer period of detection of evident changes in adult fish assemblages, reflecting longevity of adult fishes or regular stocking. YOY sampling was suggested as a useful method for assessing river ecological quality, with the ability to provide a sensitive response to the habitat structure regardless of the effect of stocking or river size.

This study was conducted to determine the effects of various time lengths of restricted feeding at 0.5% of body weight on compensatory growth (CG) in rainbow trout under summer conditions. Seven treatments with triplicate tanks consisted of control (C) fed to satiation over 98 days and the remainder being one (R1) to six (R6) weeks of restriction and then refeeding for the remaining 8 weeks of the experiment. At the end of the experiment R1 and R2 were able to catch up with C. Repeated measures anova suggested a convergence in body mass but not in body length (structure), whereas there was an association between mass and structural CG responses. Hyperphagia and transiently better food utilisation were main mechanisms of the observed CG. Organosomatic indices of the restricted groups were significantly reduced at the end of the restriction periods, but were restored to the control fish levels by the end of the refeeding period. There was a linear increase in body moisture and a decrease in lipid and lipid/lean body mass ratio with the severity of the restriction periods, but these trends vanished by the end of refeeding. The findings of the present experiment suggest that restricted feeding and the following realimentation to elicit CG as a management tool can be used in rainbow trout, but for no more than 2 weeks under summer conditions.

This research represents the first age-based demographic assessment of pearl perch, Glaucosoma scapulare (Ramsay, 1881), a highly valued species endemic to coastal waters off central eastern Australia. The study was conducted across the species' distribution that encompasses two state jurisdictions (Queensland in the north and New South Wales in the south) using data collected approximately 10 years apart in each state. Estimates of age were made by counting annuli (validated using marginal increment ratios) in sectioned sagittal otoliths. The maximum estimated age was 19 years. Pearl perch attained approx. 12 cm fork length (FL) after one year, 21 cm FL after 2 years and 29 cm FL after 3 years. Fish from the southern end of the species' distribution grew significantly more slowly than those from the northern part of its range. Commercial landings in the north were characterized by greater proportions of larger (>40 cm FL) and older (>6 years) fish than those in the south, with landings mainly of fish between 3 and 6 years of age. The observed variations in age-based demographics of pearl perch highlight the need for a better understanding of patterns of movement and reproduction in developing a model of population dynamics and life-history for this important species. There is a clear need for further, concurrent, age-based studies on pearl perch in the northern and southern parts of its distribution to support the conclusions of the present study based on data collected a decade apart.

Seasonal and size-related patterns in feeding habits of the Atlantic bonito (Sarda sarda) in the Northeast Aegean were investigated over a 2-year period May 2007 – May 2009 based on analysis of stomach contents of 134 fish ranging from 266–655 mm fork length. The fish were caught by purse-seine boats operating around the islands of Lesvos and Chios (Greece). Of the stomachs examined, 46% contained at least one prey item and significant seasonal and size-related patterns were found in the occurrence of non-empty stomachs. The overall diet composition in terms of numerical importance was 71% fish, 28% crustaceans and 1% cephalopods. Of the fish, Engraulidae (Engraulis encrasicolus) were the dominant prey taxon, followed by Centracanthidae (Spicara spp.) and then Clupeidae (Sardina pilchardus). Statistically significant monthly variation in diet was apparent, suggesting that S. sarda take advantage of seasonally abundant prey fish in the study area, but no size-related variation in the importance of the main prey species was detected.

Length–weight relationships (LWRs) are described for 23 fish species (five indigenous species and 18 exotic species) in Lake Erhai, a plateau deep lake located in southwestern China. Four different types of fishing gear were used in order to include all possible length ranges from 2009 to 2012. Results show that the exponent b ranged from 2.72 to 3.79. The length of the growth inflection point between juveniles and females of Pseudorasbora parva and Micropercops swinhonis coincides with the length at which 50% of the females are sexually mature, respectively. The LWRs of P. parva and M. swinhonis are affected by sexual dimorphism, and Hemiculter leucisculus shows significant differences between juveniles and females. In addition, the first LWR records for nine species are provided in this study.

Cage culture of freshwater prawns in open waters is prone to the entry of predators and competitors that particularly hamper production. This study was conducted to determine how smaller net mesh sizes to reduce entry of unwanted species inside the cages affects the production of Macrobrachium rosenbergii in lake-based cages. Juvenile prawns were stocked in cages (7 × 7 × 1.5 m) of two net mesh sizes at 10 individuals m⁻² and cultured for 10 months in a shallow eutrophic lake in the Philippines. The two net mesh sizes were either 5 mm-mesh B-nets or and 1 mm-mesh Hapa nets. Each treatment had four replicates each and was fed based on biomass with commercially formulated feed. Monitoring of various production parameters was done during the two phases of culture: batch phase on days 63 and 127 and the selective harvest phase on days 187, 219, 253, 281 and 313, when the experiment was terminated. For the first 127 days of culture, the weight, percent weight increase, daily growth rate (DGR), specific growth rate (SGR), yield and feed conversion ratio (FCR) were significantly better in prawns reared in the Hapa compared to the B-nets. During the selective harvest phase the blue claw, orange claw and berried females were selectively harvested and the remaining prawns returned to the cages. After changes in stocking density through culling, ancova was used to compare the effect of mesh size with the total number of prawns returned to the cages as a covariate. Yield was significantly higher in the Hapa nets. Weight, DGR, SGR and FCR were also consistently higher in the Hapa nets, although not always significantly different. The overall better performance of prawns reared in the Hapa net cages was due to: (i) the reduction in the entry of predator and competitor species in the finer-meshed Hapa compared to the larger mesh B-net, (ii) more natural food trapped inside the Hapa cages, and (iii) a higher number of selectively harvested prawns, which decreased stocking density in the cages and improved growth. Use of small mesh size nets is recommended in the cage culture of M. rosenbergii in inland natural water bodies.

The aim of this study was to investigate effects of fish oil replacement by sesame oil in combination with other vegetable oils in diets with regard to growth performance, feed utilization, desaturation and elongation, whole fish and liver fatty acid profiles of juvenile rainbow trout. Sesame oil (SO) used in the feeds was a mixture of linseed (LO), sunflower (SFO) and fish oil (FO), whereas the control diet contained only FO. Duplicate groups of 60 rainbow trout (~7 g) held under similar culture conditions were fed 2% of their body weight per day for 75 days. At the end of feeding trials, there was no difference in feed utilization efficiency or growth performance between the control group and the groups with added sesame oil (P > 0.05). However, viscerosomatic and hepatosomatic index values were significantly higher (P < 0.05) in fish fed with FO30/SO35/SFO35 diets. Results showed that total body lipid levels of fish fed diets containing sunflower oil were higher than in the other experimental groups (P < 0.05). However, crude lipid levels were similar in fish fed the control diet and the diet with sesame oil (FO30/LO35/SO35), which is sunflower oil-free. Crude lipid levels of fish livers were not influenced by the diets (P > 0.05). Diets with sesame oil increased desaturation and elongation of 18 : 3n-3 towards n-3 HUFA. The conclusion was that the diet addition of sesame oil in combination with other vegetable oils increased the nutritional quality of the whole fish and liver of juvenile rainbow trout, in particular the docosahexaenoic acid (DHA) level. Therefore, sesame oil may be of interest for use in aquaculture.

The effects of increasing codend mesh size from 11.6 to 25 and 28.7 mm (inside stretched mesh) on the selectivity of greater lizardfish (Saurida tumbil), squid (Loligo sp.), and penaeid shrimp caught by an inshore otter trawling fishery at Nha Trang City, Vietnam were assessed. The proportion of escaping trash fish from the studied codends was also examined. In general, the lengths at 50% retention (L₅₀) of the studied species increased with increasing codend mesh size. L₅₀ values of greater lizardfish for the 25 and 28.7 mm codends were 109.4 and 145.9 mm, respectively. The 11.6, 25, and 28.7 mm codends selected shrimp at L₅₀s of 8.33, 11.86, and 13.92 mm, respectively, and squid (mantle lengths) at 13.1, 36.1, and 41.9 mm, respectively. The mean proportions of escaping trash fish were 0.06, 0.68, and 0.85 for the three codends, respectively. A minimum mesh size of 25 mm is a good compromise between management goals and fishery demands.

The present study investigated the spawning behaviour of the spiny eel, Macrognathus pancalus, and its relationship with the environment (photoperiod and temperature). The results show that M. pancalus breeds during February to September with peak spawning during February/March and July/August, indicating two main breeding periods. Initiation of breeding occurs during increasing day lengths in early spring (February/March), and regression during decreasing day lengths in autumn (September/October). The breeding status confirmed by gonadosomatic index (GSI) and ovarian histology showed six stages of ovarian maturation (viz. stage I: chromatin nucleaolar; II: perinucleolar; III: cortical alveolar; IV: vitellogenesis; V: ripe; and VI: partially spent), with predominance of one or more stages at a particular time of the year. Males also followed a similar seasonal pattern in gonadal maturation as reflected by their GSI. Results show that M. pancalus is a seasonal breeder with bimodal spawning activity. The breeding pattern suggests an influence of prevailing day length conditions at this latitude.

Changes in fatty acid composition, cholesterol and fat-soluble vitamins were studied during development (fertilized eggs, yolk-sac larvae, and after yolk resorption of shabbout, Barbus grypus). Significant differences were found in the monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFA), PUFA/saturated fatty acids (SFA), ∑n-3 and eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) ratios between eggs and larvae (P < 0.05). Significant differences were also observed in the C14:0, C16:1n-7, C18:1n-9, C18:3n-6, C20:0, C20:4n-6, C24:0, C24:1, C22:6n-3 fatty acids between eggs and larvae after yolk-sac resorption (P < 0.05). Vitamin α- Tocopherol and retinol content increased during embryogenesis, but changes were insignificant in retinol acetate, δ-Tocopherol, K1, K2 and cholesterol content between eggs and larvae after yolk resorption (P > 0.05).

This paper provides length–weight relationships estimated for five fish species (four families) economically important not only to the local community, but to the larger Indo-Pakistan sub-continent. All fish were collected from the Manora Channel and backwater creeks near Karachi, Pakistan in the northern Arabian Sea during July 2000 to October 2002. These represent the first reports of length–weight data for two species (Sardinella sindensis and Pomadasys stridens) while also providing additional data on the remaining three species (Alepes kleinii, A. melanoptera, and Liza carinata) for which limited information was available. Estimated b values obtained for the six species ranged from a minimum of 2.310 for L. carinata to a maximum of 3.082 for S. sindensis.

The study purpose was to investigate the reproductive biology, growth and length-weight of the Turkmenian crested loach, Metaschistura cristata, in the Radkan River of northeastern Iran. Age and growth are described for 1029 specimens from January 2009 to December 2010. The sex ratio was 1:1. Maximum age, based on opercula readings, was 6⁺ years for both sexes. Specimens ranged in size from 24 to 98 mm total length and weighed from 0.08 to 7.32 g. The length-weight relationships were described as W = 0.005166 TL^3.225 (R² = 0.97) for males and W = 0.006192 TL^3.125 (R² = 0.97) for females. Growth was expressed in length and the von Bertalanffy growth parameters were estimated as L_∞ = 354.9 mm, k = 0.0038, t₀ = −26.82 for males and L_∞ = 339.0 mm, k = 0.0043, t₀ = −24.88 for females. Growth performance indexes were also estimated as Φ′ = 6.17 for males and Φ′ = 6.20 for females. The gonadosomatic index showed that peak reproduction occurred during April and June, with highest average values of 2.1% for males and 25.3% for females in May. Oocyte diameter ranged from 0.09 to 1.58 mm, with a mean value of 0.54 ± 0.42 mm.

The objective of this work was to evaluate the sperm motility of 13 Steindachneridion parahybae males using open-source software (ImageJ/CASA plugin). The sperm activation procedure and image capture were initiated after semen collection. Four experimental phases were defined from the videos captured of each male as follows: (i) standardization of a dialogue box generated by the CASA plugin within ImageJ; (ii) frame numbers used to perform the analysis; (iii) post-activation motility between 10 and 20 s with analysis at each 1 s; and (iv) post-activation motility between 10 and 50 s with analysis at each 10 s. The settings used in the CASA dialogue box were satisfactory, and the results were consistent. These analyses should be performed using 50 frames immediately after sperm activation because spermatozoa quickly lose their vigor. At 10 s post-activation, 89.1% motile sperm was observed with 107.2 μm s⁻¹ curvilinear velocity, 83.6 μm s⁻¹ average path velocity, 77.1 μm s⁻¹ straight line velocity; 91.6% were of straightness and 77.1% of wobble. The CASA plugin within ImageJ can be applied in sperm analysis of the study species by using the established settings.

The aim of the study was to identify the diet composition, feeding preferences, size and sex related diet changes, and to calculate the consumption rates of common dolphinfish, Coryphaena hippurus, in the eastern Arabian Sea. Fish were caught using longline gear during the years 2006–2009. Stomachs of 238 specimens with fork lengths ranging from 324 to 1250 mm were analysed; 72 (30.25%) of the stomachs were empty. Epipelagic finfishes were the predominant prey followed by cephalopods and crustaceans. Occurrence of items such as sargassum, sea fans, corals, plastics and pieces of wood in the stomachs indicate an opportunistic and voracious feeding nature. Flyingfishes (family Exocoetidae), especially Exocoetus monocirrhus (%IRI 16.92), dominated the diet. Unidentified filefishes (family Monacanthidae), Sthenoteuthis oualaniensis, Euthynnus affinis, Cheilopogon furcatus and Cubiceps pauciradiatus were other important food items. The diet varied between sexes and different size classes. Juveniles and adults (size classes <75 cm, 75–95 and 95–115 cm) fed mainly on epipelagic finfishes, whereas the large adults (>115 cm) fed preferentially on cephalopods. Food consumption rate was higher in females (6.37% BW day⁻¹) compared to males (4.04% BW day⁻¹), and increased with their increase in size up to 75–95 cm length classes, thereafter decreasing. The daily meal and daily ration was 332.63 g day⁻¹ and 5.25% BW day⁻¹, respectively, and average annual food consumption was 121.41 kg.

Annular seabream, Diplodus annularis (Linnaeus, 1758), were caught off the coast of the Gulf of Gabes (Southern Tunisia, Central Mediterranean) between April 2008 and March 2010 by commercial catches. With a total 2066 specimens the fish ranged in size from 7.7 cm to 18.5 cm total length and from 7.5 g to 123.3 g in weight. Changes in biological parameters (weight, length, gonadosomatic index, hepatosomatic index and condition factor) were examined in order to provide information on the spawning period and reproductive cycle in the gulf. Overall sex ratio was 1 : 1.52 in favour of females. The reproductive season extends from March to June, with a spawning activity peak in May. Total length at sexual maturity was 10.5 ± 0.22 cm (males) and 10.6 ± 0.3 cm (females). The results of this study could help to establish a recommended minimum capture size.

This study is based on a 23-year sampling of fish and compares raw population abundance and biomass obtained from three to six consecutive electrofishing passes in a small lowland stream in Poland, with values of calculated density and a biomass from the Zippin model. Three density estimates and four biomass estimates obtained with three passes were higher than those estimates based on six catches. This discrepancy occurred because fewer fish were collected in the first pass than in the second pass. However, when the six consecutive passes were considered, the higher raw abundance and biomass in the second pass did not produce any significant error in the density calculation. A catchability decline resulted from the low number of juvenile fish captured when there was a high number of fish that had successfully spawned in a given year. Nevertheless, fish density assessment on the basis of three runs in lowland streams is recommended for quantitative sampling, and the problems that sometimes emerge will be explained in this study.

The present study was undertaken to assess length-weight relationships (LWRs) of Wallago attu (Bloch and Schneider, 1801) from Manchar Lake, in Pakistan. A total of 251 specimens collected from August 2011 to April 2012 were examined. Length-weight equations were W = 0.00464 L ^3.0819 (combined), W = 0.00387 L ^3.120 (males) and W = 0.00632 L ^3.00892 (females).

This study deals with the question as to whether antibodies established for mammals are also specific for rainbow trout. The reason for this examination is the major economic importance of rainbow trout in aquaculture and the growing scientific attention. However, there are few primary antibodies so far defined for this fish species. Therefore, the aim of the current study was to test the ability of 15 commercially available antibodies for rainbow trout in an indirect immunofluoresence assay to analyse tissue sections of organs. Five commercially available primary antibodies were identified, which were directed against proteins of one or two organs/ cell types in rainbow trout.

Sharks of the genus Carcharhinus exhibit subtle morphological differences that are difficult to observe because of the common practice of head and fin removal, making species identification challenging. A total of 317 sharks, commonly called ‘cação-baia’ (large individuals) or ‘machote’ (small size) in Brazil, were captured by the tuna fleet at the Santos and Guarujá fishery ports on the southeastern coast of Brazil and identified at the species level by multiplex PCR. The Internal Transcribed Spacer 2 region of ribosomal DNA was amplified using universal primers, and species-specific primers were used for some of the Carcharhinus species. A total of 313 shark carcasses were directly identified by multiplex PCR. Four carcass samples did not amplify; therefore, the partial COI sequences were used to confirm their taxonomic identity. The results show that more than one species was being traded under the same commercial designation, including some Carcharhinus species that are under protection by federal legislation. Such species misidentification directly affects the long-term sustainability of sharks.

The diet of the milk shark, Rhizoprionodon acutus, from the Senegalese coast (12°30′N–14°45′N) was investigated in 3600 specimens with total lengths ranging from 44 to 113 cm for females and from 45 to 110 cm for males. Conducted from May 2010 to April 2011, the study revealed that of the 3600 stomachs examined, 577 contained food (16.03%). Cumulative prey diversity curves reached a stable level at 175 stomachs and thus the sample size was large enough to describe the overall milk shark diet. Relevant differences in the diet were found between sexes, maturity stages, sampling seasons and locations. The milk shark diet was composed of teleosts, crustaceans, mollucs, nematodes, annelids, and unidentified invertebrates. R. acutus seemed to have a preference for teleosts (98.75% in terms of IRI). The trophic level of milk shark calculated in this study was 4.2.

In this study the intraspecific variation of wild Labeo rohita was investigated on the basis of morphometric characters using the truss network system constructed from the fish body. Altogether 435 fish samples were collected from six drainages of the Ganga basin in India. Data were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. The first principal component (PC1) explained 47.88% of the total variation, while PC2 and PC3 explained 17.22 and 8.33%, respectively. The step-wise discriminant function analysis retained three variables that significantly discriminated the populations. Using these variables, 62.3% of the original groups were classified into their correct samples and 53.1% of the cross-validated groups omitting one procedure were classified into their correct samples. Misclassification was higher for samples from the River Gomti (28.6%). Of the total of 31 transformed truss measurements, 30 exhibited significant differences among populations. These findings indicate the presence of six different stocks of L. rohita in the Ganga basin.

The aim of this work was to compare the morphometric and meristic characteristics of whitemouth croaker, Micropogonias furnieri, from two different areas: the Río de la Plata (to the west) and the oceanic coast (to the east) during the summer spawning season (December 1999), and to determine whether they constitute one demographic unit or independent management groups. Data from 966 whitemouth croakers were analysed for stock discrimination between areas. The results provided further evidence that the two cohorts differ significantly in these areas. However, an important misclassification of individuals was found. The morphometric variables that contributed more to discriminate the groups were mouth length, head length, horizontal eye diameter and length of the pectoral fin. Misclassified individuals from the western and eastern groups have shown that whitemouth croaker do not display high fidelity to their known spawning grounds. The well-classified and misclassified individuals for the western and eastern groups were found to be mature and in spawning condition, representing between 82–84%, and 66–88%, respectively. These results support the hypothesis of contemporary gene flow between the Río de la Plata and coastal Atlantic populations. Despite the misclassified individuals, morphometrics presented in this study and genetic information originating from other studies show differences between Río de la Plata and oceanic groups, and predict the two-stock hypothesis. Problems related arising from these mixed population groups and potential implications for managements are discussed.

The two stocks of cod (Gadus morhua L.) in the Baltic Sea are separated by two main spawning areas and main spawning periods. Migrations of juveniles and adults result in the mixing of both stocks. At present, the two stocks have been discriminated using inter alia meristics and morphometry, genetics and tagging experiments. However, using these techniques it is not possible to assign single, non-spawning individuals to a certain stock. Since otolith shape analysis has become a common method for stock discrimination and has been applied successfully to several Atlantic cod stocks, it was applied here for the Baltic cod stocks. To obtain baseline samples, spawning cod were sampled between 2005 and 2009 in the main spawning areas during the spawning periods. The otolith contours were digitized and elliptical Fourier descriptors were analyzed. Both stocks differed significantly in their otolith shapes, and individuals could be allocated with >90% accuracy to one of the stocks. Both Baltic cod stocks and cod from West Greenland were discriminated with 93% correct classification. These results highlight otolith shape analysis as a useful tool to discriminate adults of Baltic cod stocks.

Routine metabolic rate (RMR, mgO₂ g⁻¹ h⁻¹) and critical oxygen concentration (Pc, a hypoxia tolerance indicator, mgO₂ L⁻¹) were determined in larvae and juveniles of round crucian carp, Carassius auratus grandoculis Temminck & Schlegel 1846, by measuring oxygen consumption at 15°C, 20°C, and 30°C. In addition, the dependence of RMR and Pc on fish body weight (W, g) and temperature (T, °C) was examined to construct minimal mathematical models. RMR depended on W and showed smaller values in larger individuals. RMR was different among the three temperature conditions and showed higher values at higher temperatures. Pc was significantly related to W and was low in larger individuals; that is, larger individuals had a higher hypoxia tolerance. In contrast, Pc was independent of temperature, implying that seasonal temperature fluctuations do not cause seasonal disequilibrium of hypoxia tolerance in round crucian carp. The RMR and Pc models were RMR = 0.0674W^−0.193e^0.0562T and Pc = 1.35W^−0.107, respectively. The metabolic information clarified in this study is essential for habitat quality assessments and aquaculture management of this species.

This study evaluated the effect of different doses of the antioxidant α-lipoic acid (LA) administered by intraperitoneal injection on the detoxifying capacity (activity of glutathione-S-transferase, GST) and oxidative damage (lipids and proteins) in the pompano, Trachinotus marginatus. The plasma glucose levels showed that there were no differences between the treatments (P > 0.05). In the brain, GST activity was significantly higher (P < 0.05) in fish injected with 40 mg LA kg⁻¹ when compared with the control group. In the muscle, GST activity was not influenced by LA treatment (P > 0.05). In the liver, fish injected with 20 mg LA kg⁻¹ showed higher GST activity than the control group (P < 0.05); however, higher doses (40 and 60 mg LA kg⁻¹) led to a reduction of GST activity in the liver, which was comparable to that observed in the control group (P > 0.05). The two highest LA doses (40 and 60 mg kg⁻¹) had opposite effects, depending on the tissue examined: LA was an antioxidant in the brain, reducing lipid peroxidation (P < 0.05), and a pro-oxidant in the liver, augmenting oxidative lipid damage (P < 0.05). The latter effect was accompanied by an increase in the free iron concentration in the liver at higher LA doses. These results indicate the need to thoroughly evaluate the antioxidant effects on aquatic organisms, since at some doses and/or in some organs their beneficial effects can be lost.

Feeding and stable isotope analyses for Bythaelurus canescens individuals were conducted to describe the diet of B. canescens as well as infer their potential prey species in the community. Stomach content analysis and mixing models by ratio isotopes composition were used to infer the food habits and calculate the trophic level of the dusky catshark, B. canescens. The results showed siphonophores and cephalopods as the most important food in the diet (67.9 and 20.2%, respectively). Calculated trophic level was 3.9, indicating that B. canescens is a meso-predator in the upper continental slope communities off Chile. By mixing models based on isotope data it can be inferred that the probabilities of the consumption cephalopods and siphonophores would be 36.7 and 15.2%, respectively.

Seasonal growth of Galaxias maculatus in Tierra del Fuego, at the southern limit of its distribution, can be explained by the variation in extrinsic factors, and experiments with fasting in summer conditions would allow researchers to focus on the potential feeding/fasting conditions independent of other seasonal cues, and thus distinguish the effect of fasting from other winter factors influencing fish growth. The study presents information on muscle growth in G. maculatus as well as the results of an experiment evaluating the effect of fasting on the growth rate, total muscle growth and energy density in this species under summer-like conditions. A uniform pattern of muscle fibres suggests the absence of mosaic hyperplastic growth in G. maculatus. Hyperplasic growth was completed before puyen reached 65 mm total length, and hyperplasia cessation was correlated to the transition from the juvenile to the adult stage. In the experimental fish, where hypertrophic growth was the unique process responsible for adult muscle growth, fasting decreased mass, condition and energy density of the individuals, and stopped hypertrophic growth. These results are proof that reduced food consumption in southerly puyen populations during winter might contribute to the seasonality of the growth previously reported for this species. A provisional summer growth rate of 2–3 mm/month is suggested for populations inhabiting the southern limits of this species' distribution. G. maculatus is thus proposed as a useful model species to study hypertrophic muscle growth.

This paper provides the length-weight relationship (LWR) and other biological information of a threatened plateau freshwater fish species Ptychobarbus chungtienensis in the subfamily Schizothoracinae of the family Cyprinidae, from the Bita Lake of Shangri-la, in Yunnan, China. The LWR was BW = 0.00954 TL^2.95 for a total of 392 individuals, where the coefficient b was close to 3.0, suggesting a near-isometric growth in this species. The total length: standard length relationship was TL = 0.399 + 1.151 SL. Fitting a von Bertalanffy growth function to the observed length-at-age data resulted in L_(t) = 53.1 (1-e^{−0.08(t−0.2)}). The natural mortality rate (M) was 0.20 year⁻¹. Length at first maturity (Lm) was 20.57 cm, and 6.3 years the theoretical estimated age at first maturity (Am). Ptychobarbus chungtienensis mature gradually beginning in May, reaching a reproduction peak around August, with most individuals completing reproduction by October. The gonadosomatic index (GSI) was highest in August (GSI = 0.1351) and lowest in October (GSI = 0.0467). The male index (GSI = 0.0866) was lower than in females (GSI = 0.1466) (P < 0.05). Mean condition factor (Km) of P. chungtienensis was 0.8500, and not significantly different between sexes (P = 0.124), but differing significantly between seasons. In October the condition factor (Km = 0.9211) was significantly higher than in May (Km = 0.8379) or in August (Km = 0.8412) (P < 0.05).

The length–weight relationships (LWR) for three fish species collected in Sirwan River, located in Kurdistan and Kermanshah provinces, western Iran, were estimated. The values of the slope parameter (b) in the length–weight relationship equations were determined as 3.086 for Alburnus mossulensis, 3.382 for Alburnus filippii and 3.425 for Capoeta damascina, all significantly different from the expected b = 3 value, indicating a positive allometric growth pattern for all the three species.

The present study describes the length-weight relationships (LWRs), length-length relationships (LLRs), Fulton's condition factor (K_F), size at first sexual maturity, spawning season, sex ratio and fecundity of the Morari Aspidoparia morar (Hamilton, 1822) (Cyprinidae). Sampling was done using traditional fishing gear jhaki jal (cast net) from July 2010 to June 2011. Total length (TL), fork length (FL) and standard length (SL) were measured with digital slide calipers. Individual body weight (BW) and gonad weight (GW) were determined to an accuracy of 0.01 g for all specimens. The gonadosomatic index (GSI) was calculated and size at first maturity for males and females estimated using GSI and TL as indicators. Female ≥ size at first maturity was used to determine fecundity. A total of 1200 specimens (males = 552, females = 648) ranging from 4.06–12.84 cm TL and 0.53–16.75 g BW were analyzed. The overall coefficient b for the LWR indicated positive allometric growth (>3.00) in males and isometric growth in females (~ 3.00). ancova (analysis of covariance) revealed significant differences between males and females (P < 0.001). All LLRs were highly correlated (r² > 0.973, P < 0.001). Sizes at first sexual maturity for males and females were 6.0 and 7.0 cm TL, respectively. K_F changed little throughout the year and GSI peaked in November to April, indicating the spawning season (GSImax = 15.0 in females, 2.0 in males). Mature females were dominant during the entire spawning season except in April. Mean total fecundity was 6700 ± 3500, ranging from 1860 to 19680. In addition, relative fecundity ranged from 190 to 1200 (mean 560 ± 235) in the Jamuna River. To ensure sustainable management of this species, the protection of mature individuals during the peak spawning season is highly recommended.

The movement characteristics of Pacific oyster trochophores have received very little coverage in the scientific literature. Described here are not only changes in the swimming characteristics of Crassostrea gigas trochophores (size: 53–77 μm) in relation to time after fertilization and to inter-female variation but also the effects of salinity and pH on movement characteristics. The percentage of motile trochophores was measured on images obtained through a dissecting microscope and the Velocity Average Path (VAP) was assessed using a Computer Assisted Sperm Analysis (CASA) system. At 20°C, the first movements of the trochophores were observed at 6.5 h post-fertilization. The mean (± SD) percentage of swimming trochophores and the VAP observed in seawater at 11.5 h post-fertilization were 85 ± 10% and 146 ± 75 μm s⁻¹, respectively (n = 8 females). Significant inter-female variation in the percentage of motile trochophores (range: 66 ± 16–93 ± 3%) and in the VAP (55 ± 47–180 ± 90 μm s⁻¹) was detected. Most of the trochophores were motile in a 9‰ salinity solution. Adjusting the pH of the seawater to values from 5.10 to 9.08 had no effect on swimming characteristics. The present study shows that the movement of oyster trochophores exhibits high plasticity in relation to environmental conditions because the highest percentages of swimming trochophores and optimal velocity values were recorded within large ranges of salinity and pH. Further research is required to determine whether the swimming performances of trochophores can be used to assess embryo quality in commercial hatcheries.

In order to estimate the population dynamics of the hilsa shad, Tenualosa ilisha, fishery in Sindh, the key population parameters of growth, mortalities, recruitment pattern, exploitation and maximum sustainable yield are discussed. Length frequency data were collected from April to October 2004 from the main commercial (hilsa) landings at Thatta, Sindh. Estimated parameters of the von Bertalanffy (Hum. Biol. 10, 181–213) growth model were L_∞ = 31.5 cm, K = 1.5 year⁻¹, t₀ = −0.10 year as obtained by the electronic length frequency analysis (ELEFAN I). Estimated natural, fishing, and total mortalities were 2.21, 0.673, 2.89 year⁻¹, respectively. The relative biomass per recruit (B′/R) was 0.95 and yield per recruit (Y′/R) was 0.06 using the knife-edge selection. The exploitation ratio at the maximum sustainable yield (MSY) was E_max = 1.0 year⁻¹, fishing mortality at MSY was F_max = 2.89 year⁻¹, average target F_opt = 0.5 year⁻¹ and F_limit = 1.47 year⁻¹. The catch and effort data from 1981 to 2004 (MFD, Karachi) were analyzed using the catch and effort data analysis (CEDA) computer programme. Estimated biological reference point of MSY for the Fox model was 891 tonnes (t), R² = 0.75; for the Schaefer and Pella-Tomlinson models MSY = 744 t, R² = 0.49, the outputs of which appeared to be more conservative than the Fox model which indicated a better fit. The overall situation of hilsa fishery is in severe stress and appears vulnerable to overexploitation. On the basis of the present findings, serious attention is required to provide appropriate access of the fish to the Indus River during the spawning period as well as to impose a ban on fishing during upstream migration and on undersized catch to prevent this traditional fishery in this area.

Intersexual gonads were detected in three clupeiform species, Sardinops melanostictus, Sardinella zunasi and Englaulis japonicus, collected in Tokyo Bay off Yokohama City, Japan, of which appearance rates were 18.2, 34.6 and 33.9 %, respectively. While spermatogenesis proceeded normally in these individuals, previtellogenic stage oocytes were detected outside of the testes in the hermaphrodites, appearing as a single cell or small clusters. The results suggest that these species are non-functional hermaphrodites. As intersexual gonads have been reported in other clupeiform species collected before significant pollution and/or at sites far from urban influences, such non-functional hermaphrodites may be common occurrence in the order. However, high rates of hermaphrodite appearance also suggest the possibility that the development of these oocytes were induced by environmental estrogens.

Sex steroid changes during temperature-induced gonadal differentiation were evaluated in the olive flounder, Paralichthys olivaceus. Larvae were reared at 21 ± 0.5°C, 24 ± 0.5°C and 28 ± 0.5°C from day 40 post-hatching (dph) to 90 dph. The proportion of males was 61.1, 76.7, 87.8 and 47.8% in 21°C, 24°C, 28°C and in control groups, respectively. Gonadal differentiation was circa 65 dph, when fishes were a mean 39 mm total length (TL). The gonads developed faster when fishes were reared in higher temperatures. Radioimmunoassay (RIA) analyses indicated that the level of estradiol-17β (E2) changed during the period of gonadal differentiation and peaked at an onset of ovarian differentiation in all groups. Compared with fish in control groups, the levels of E2 were lower in thermal-treated groups, especially in the highest temperature groups. The present results indicate that E2 plays a major role in the process of ovarian differentiation, and suggest that temperature-induced masculinization in P. olivaceus is mainly due to a decrease in the E2 level during the period of ovarian differentiation.

The silver pomfret (Pampus argenteus) is a commercially important species native to the Indo-western Pacific area. In the present study, the genetic structure of five P. argenteus populations from the Arabian Sea, Bay of Bengal, and South China Sea were investigated using sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. All populations showed high levels of haplotype diversity (h) and low levels of nucleotide diversity (π). Phylogenetic trees indicated that the haplotypes could be divided into three clusters, indicating the geographic distribution of the five populations. Analysis of molecular variance (amova) indicated the intra-region variation among these populations to be highly significant. The average pairwise differences and F_st values among the three regions were also found to be significant. These results suggest that P. argenteus in these regions has strong geographic genetic structure. The present results provide new information for the genetic assessment, fishery management, and conservation of this species.

Passive Integrated Transponder tags (PIT tags) are recommended as the most suitable method for tagging fish on the basis of their high retention and fish survival rates. The objective of this study was to determine the long-term effects (between 1 and 11 years) of the PIT tag on the growth of the yellow European eel (Anguilla anguilla). A difference of more than 50% was observed in the growth of marked and unmarked yellow eels. If this is a general long-term effect in all eels, it would seriously restrict the use of PIT tags for studying the dynamics of European eel populations, and so for their management.

Morphology, meristics, and molecular genetics tools were used to determine the species level identification of the most commonly landed sardine species in the Philippines. Results from this study indicated that the historical and widely applied nomenclature of the Indian oil sardine, Sardinella longiceps, is incorrect and that this species is instead the Bali sardinella Sardinella lemuru. Developing an effective strategy for managing one of the Philippines most important commodity sardine species first requires accurate identification of this species. Results of this study provide needed information that is now being applied to emerging management policies.

Total length (L_T) and total weight (W) measurements of 2576 European eels (Anguilla anguilla) immediately after sampling and again after freezing and defrosting showed that freezing significantly reduced eel L_T and W by 1.3 and 6.4%, respectively (P < 0.001). Two formulas for the correction of L_T and W of eels after defrosting are given.

Elasmobranchs are an important catch component in Tunisian artisanal fisheries. Generally, species-specific information is largely unavailable for artisanal fisheries; an increase in knowledge thereof is essential to ensure proper management of these species. The study analyzed the gillnet fishery elasmobranch catches in the Gulf of Gabès, whereby 45 fishing trips were conducted from April to June 2007 and 2008 for the capture of a total of six species: three Rajiformes and three Carchariniformes. Rhinobatos cemiculus was the most important species (52%; 4.588 ind km⁻² net per day). Among shark species, Mustelus mustelus was the most important (66.8%; 2.21 ind km⁻² net per day). Discards represented 6.87% of total catch in weight and 14.28% in number of specimens caught. Size composition of captures varied by species, but usually mature, mainly gravid females were abundant. Further investigations are needed to obtain more information on such fragile species for the development of protective measures.

The life-history traits of Aphanius danfordii in Hirfanlı Reservoir were studied on the basis of 2252 specimens caught between April 2008 and April 2009. Maximum age was determined as five years for both sexes. The overall sex ratio of males to females was 1 : 1.21; however, this ratio varied by age and season. Mean total length at age data derived from scale readings were used to estimate growth. The von Bertalanffy growth parameters were: L_∞ = 126.63 mm, K = −0.09, t₀ = 2.35 for females; and L_∞ = 61.2 mm, K = −0.19, t₀ = 2.76 for males. The gonadosomatic index (GSI) values indicated spawning to be from May to September. Absolute fecundity varied from a minimum of 143 eggs for age one to a maximum of 698 eggs for age five. Relationships between fecundity–length and fecundity–weight were described by the equations: F = 0.0002 TL^3.3222 and F = 36.032 W^1.0053, respectively. The equation of the relation between absolute fecundity and age was F = 25.372 t^1.2343.

During exploratory surveys in the tributaries (Penganga and Satnala) of Godavari and (Bheema) Krishna basins, specimens of mahseer were collected. The morpho-meristic characteristics of these specimens conformed to the taxonomic keys for Tor tor. The mitochondrial COI sequences of these specimens clustered with the T. tor specimens from the River Narmada and were distinct from the other mahseer such as T. khudree and T. mussullah, which are known to exist in the rivers of the region. This confirmed the distribution of T. tor in the rivers of peninsular India and indicated an extended distribution of the known range. The major predominating habitat characteristics of collection areas were cobbles mixed with gravel, and a riparian cover of shrubs and trees. The occurrence of fingerling size specimens in the river suggests that the species has adapted and is likely to have established self-recruiting populations in these rivers.

This study concerns the reproductive strategy of the freshwater fish, Leporinus piau, native to the Brazilian semi-arid region. The hypothesis of this work predicts that the species would spawn during the rainy season, presenting a seasonal reproductive strategy. The study investigated the structure of total body length and body mass, sex ratio, body size at first sexual maturity, developmental stages of gonads, fecundity, gonadosomatic index (GSI), condition factor (K) and the spawning season of L. piau. Twelve monthly samplings (mean n = 18) were carried out in 2009 and environmental parameters such as rainfall, temperature, pH, electrical conductivity and concentration of dissolved oxygen of water were registered. The sampled population of L. piau (n = 211) showed a slight predominance of males (55%), but with larger and heavier females. First sexual maturation in males occurred earlier (16.5 cm total length) than in females (20.5 cm total length). The species is a total spawner with an average fecundity of 55 000 mature oocytes. Rainfall (225 ± 7.2 mm) and concentration of dissolved oxygen (8.5 ± 0.2 mg L⁻¹) acted as influential factors during the spawning season. The monthly GSI shows that spawning starts when the rainy season is at its maximum and ends synchronously (females r = 0.91; males r = 0.89) with the end of the rainy season. L. piau presents a seasonal reproductive strategy with high reproductive output, providing a population increase and exploitation of the environmental resources.

Length–weight relationships (LWR) of fish serve as building blocks in ichthyology and fishery science. In this study LWR knowledge is extended to some species, regions and sizes of fish either incomplete or missing from the literature or from the online databank (FishBase). For several species data are presented for the first time, while other entries are improved and expanded. Organisms were captured by trawl from the continental shelf of the Israeli coast, where fishes were hypothesized as being small due to low productivity and high water temperatures – a phenomenon called ‘Levantine Nanism’. Despite this, for nine of the 43 species presented here the maximum length values exceeded their L_max in FishBase. The dominance of fishes of Indo-Pacific origin among the species with exceptionally large specimens (7 of 9) is in agreement with Bergmann's rule; it is thus hypothesized here that these large specimens result from the low temperatures in the Mediterranean compared to their warm Indo-Pacific sources. This is an example of the superb adaptation of tropical species to the Mediterranean and suggests that Levantine Nanism may be limited to indigenous species.

In order to determine the present benthic fish fauna in the Sea of Marmara, sampling was conducted at a total of 10 stations for 2 weeks in August 2009, using a commercial twin beam trawling vessel with 18 and 36 mm stretched mesh sizes at the cod-end. In addition, some physicochemical parameters that play important roles, such as temperature, salinity, dissolved oxygen, and pH, were measured for each station. As a result, 31 fish species from 23 families were found at a total of 10 stations in depths of 30–1000 m. At each station, the Shannon–Weaver diversity index, Simpson dominance index, species richness index, and evenness index were estimated. This study reports on species composition of the demersal fish catches in the Sea of Marmara for a preliminary assessment of the status of these fish communities.

A comprehensive literature review on prevalence and distribution of parasites of the European eel (Anguilla anguilla) in European waters was conducted to set a baseline for future trend analyses and biodiversity considerations. The resulting checklist compiled from peer reviewed journals as well as grey literature including scientific reports, conference contributions, PhD theses and own survey data includes all protozoan and metazoan parasites of the European eel from freshwater, brackish and marine habitats. Parasites are arranged according to phylum and family. Species within families are listed alphabetically. Infected host organs, recorded habitats, localities, countries and literature citations are provided for each species. A total of 161 parasite species/taxa from 30 countries are listed. With the trypanorhynch cestode Tentacularia coryphaenae a new host record could be documented. Furthermore, three new locality records of parasitic nematodes could be added based on own survey data: Anisakis simplex from an eel caught in the Baltic Sea, Eustrongylides mergorum for German freshwaters, and Goezia anguillae from the Tagus estuary in Portugal. Special consideration was given to the distribution of the swimbladder nematode Anguillcoloides (Anguillicola) crassus. A map and table of first reported records of this neozoan parasite species for 25 countries as well as a survey map indicating all published localities documented in the checklist are provided.

The European sturgeon, Acipenser sturio, experienced a dramatic decline during the late 19^th century in Germany. Only after its confirmed extirpation in the wild were ex-situ measures introduced as the basis of a recovery attempt. In order to achieve effective population restoration, it is important to evaluate and compare efficiency of both planned and ongoing remediation measures. For this purpose, a stochastic age-structured model of this population was developed to conduct a population viability analysis and to assess different management and restoration measures. The model revealed a high susceptibility of the species to even very low fishery and by-catch pressures of below 5%. Population recovery was shown to be a very slow process, with a minimum timeframe of 30–50 years. Continuous stocking represents an important initial management measure to accelerate population recovery, reducing by two to three times the time required in comparison to only initial stocking. Habitat remediation (e.g. spawning grounds) in the Elbe River seems necessary, as according to model estimations, the present carrying capacity could sustain no more than a few thousand adults. The model showed a clear correlation between spawning habitat availability and the sustained number of adults.

Lactic acid bacteria (LAB) are often found as sub-dominant microbial components in the gastrointestinal (GI) tract of fish and have positive effects on the host. They are generally promising candidates for probiotics and can act as substances to improving both native immune responses and growth performance of animals including fish. In the present study the Persian sturgeon Acipenser persicus autochthonous intestinal LAB were investigated. A total of 90 sturgeon fingerlings were sampled and LAB were isolated and enumerated on MRS agar. Initial identification of 47 LAB isolates using standard biochemical and phenotypic tests revealed five dominant phenotypes. Twenty-one isolates, representatives from each of these phenotypes, were subsequently identified by 16S rRNA sequence analysis. The results showed that cultivable authochthonous LAB ranged from log 2.93 to 5.61 CFU g⁻¹ intestine, with a mean of 4.38 ± 0.58 CFU g⁻¹. 16S rRNA sequence analysis revealed that the LAB community was dominated by Lactococcus spp., with Lactococcus garvieae and Lactococcus lactis accounting for 42.55 and 36.17% of the LAB population, respectively. Pediococcus pentosaceus (14.90%), Weissella cibaria (4.25%) and Enterococcus faecalis (2.13%) were identified as minor components of the LAB community. This is the first report of these LAB as members of the microbial community in the intestine of Acipenser persicus. The results show that both potentially pathogenic (i.e. Lactococcus garvieae) and probiotic (i.e. Lactococcus lactis and Weissella cibaria) LAB inhabit the Persian sturgeon GI tract. Future studies should seek to elucidate the relevance of these species to the host.

The anaethetic effects of 2-phenoxyethanol (2-PE) on possible primary (cortisol level) and secondary (hematological indices and glucose level) stress responses were studied in Persian sturgeon (Acipenser persicus). Fish were first exposed to 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1 ml L⁻¹ 2-PE, and the time to induction (deep anaethesia) and recovery were measured. At a concentration of 0.1 ml L⁻¹, 2-PE failed to induce deep anaethesia in fish, whereas at concentrations of 0.7, 0.9 and 1.1 ml L⁻¹ all fish were anaethetized within 3 min of exposure. For assessing possible stress effects caused by effective concentrations of 2-PE, the hematological indices, serum cortisol and glucose were determined in the deeply anaethetized fish as stress indicators. The 2-PE exposure resulted in significant increases in red blood cell (RBC) values at 0.3 and 0.5 ml L⁻¹; parallel increases in hemoglobin values were also observed at these concentrations (P < 0.01). Moreover, a lower concentration of 2-PE (0.3 ml L⁻¹) caused a significant increase in hematocrit values (P < 0.05). Among the hematological indices, mean corpuscular volume (MCV) values decreased at 0.5 ml L⁻¹ when compared with the control and other groups (P < 0.05). Serum cortisol level was elevated at 0.3, 0.5 and 0.7 concentrations of 2-PE (P < 0.01). The glucose level followed a trend similar to that observed for cortisol. The outcome of these experiments shows that 2-PE at a concentration of 0.9 ml L⁻¹ is a suitable anaesthetic for Persian sturgeon. This study demonstrates that rapid induction of deep anaethesia with a relatively high concentration of 2-PE (0.9 and 1.1 ml L⁻¹) was associated with the lowest effects on signs of physiological stress in Persian sturgeon.

A large feeding aggregation of Atlantic sturgeon occupies the inner Bay of Fundy during summer, presumably to forage on the intertidal mudflats. The feeding habits of Atlantic sturgeon were examined during summer 2011 in Minas Basin as description of diet is important for identifying critical foraging areas. Atlantic sturgeon demonstrated an overall preference for sandy tube-dwelling polychaetes (Index of Relative Importance (IRI) = 99.7%). Major prey taxa included Maldanidae (Clymanella sp., 52.5%) and Spionidae, primarily the species Spiophanes bombyx (41.6%). Other prey items consumed included Phyllodocidae (Eteone sp., 2.1%), Nephtyidae (2.2%), Nereididae (0.7%), and Glyceridae including Glycera dibranchiata (0.6%). Seventeen additional taxa were identified in trace amounts (mean IRI = 0.02%), including Corophidae and Mysidae. There was no significant difference in the number of prey items consumed and the fork length of the fish. Analysis of gut fullness with respect to tidal state indicated no significant difference between gut fullness on the flood or ebb tide. An overall preference for sandy tube-dwelling polychaetes may indicate that particular areas of the Minas Basin intertidal region are more important than others to these foraging fish. Considerable baitworm harvesting occurs during summer months in Minas Basin and could potentially create impacts with sturgeon consumers, both directly through competition for prey items and indirectly through change in sediment and benthic community composition.

Laparoscopy is a reliable, minimally-invasive technique to obtain reproductive information from wild and captive sturgeon. While generally considered safe, the physiological consequences of laparoscopy in sturgeon are unknown. Therefore clinical pathology changes in juvenile, Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) following experimental laparoscopy at 10 and 22°C were described. Control fish were anesthetized with MS-222 according to the same protocols as surgical fish, but were not incised. Surgical procedures did not affect heart and ventilation rates, signs of stress (skin redness) or time to recover from anesthesia in comparison to control fish. Anesthesia with MS-222 produced a transient (by 1 h) hemo-concentration (elevated protein and electrolytes), erythrocyte swelling (increased PCV and MCV) and stress response (elevated cortisol and glucose); and a delayed (by 24 h) increase in RBC, leukopenia and increased N : L ratio. Surgical procedures resulted in a delayed (by 24 h) decrease in plasma proteins, electrolytes, RBC and PCV relative to control fish, which may have resulted from surgically-induced hemorrhage. Plasma enzyme activities increased in response to anesthesia and surgery and may indicate general stress and tissue damage. Anesthesia had a greater effect on blood value response than surgery, and the proportion of effect increased with temperature as MS-222 potency and toxicity increases with water temperature. Repeated handling and blood draws within 24 h resulted in a 7% increase in cortisol, 10–14% increase in CK and 9–11% increase in LDH values. Except for plasma enzyme activities, blood values of all fish recovered within 1 week following anesthesia and surgeries. Relative experience of surgeons had no effect on hematology and biochemistry of fish, but healing rates of incisions were improved with better suture technique. Results of this study conclude that the physiological effects of laparoscopy are largely related to the anesthetic, MS-222, and are generally mild and short-lived. Improvements in laparoscopic technique might be gained by exploring alternate anesthetic protocols with faster induction and recovery times and reduced physiological effects.

A 9-week experiment was designed to study the effects of partial replacement of monocalcium phosphate (MCP) with neutral phytase on growth, body compositions, serum biochemical statuses and intestinal digestive enzyme activities of grass carp, Ctenopharyngodon idellus. The control diet (designated as P2.0) was prepared with 2.0% MCP but without phytase. The three other diets (designated as PP1.5, PP1.0 and PP0.5, respectively) were supplemented with 1.5, 1.0 and 0.5% MCP, respectively, along with 500 FTU of neutral phytase kg⁻¹ diet in each. After a 9-week feeding trial, fish (initial body weight: 43.44 ± 2.37 g) fed with PP1.5 and PP1.0 had no significant change in weight gain (WG), specific growth rate (SGR), protein efficiency rate (PER) or feed conversion ratio (FCR) compared with the control (P > 0.05) whereas fish fed with PP0.5 showed significantly lower growth performance in the above parameters. The crude lipid content in whole body or muscle of the fish fed with PP1.5 was significantly lower than the control while significantly higher in fish fed with PP0.5 (P < 0.05), whereas no obvious change was observed in the fish fed with PP1.0. For serum indices, higher serum alkaline phosphatase (Alkp), phosphorus (P) and calcium (Ca) contents were observed in fish fed with phytase-supplemented diets in comparison with the control. In addition, dietary phytase supplementation increased amylase activity and decreased lipase activity in both foregut and hindgut. The present study suggests that dietary MCP can be reduced when neutral phytase is added to the grass carp diet, and that the maximum MCP reduction level can be up to 1% when neutral phytase is supplemented at 500 FTU kg⁻¹ diet.

The reproductive cycle of the blue jack mackerel, Trachurus picturatus, had not been described for the Canary Islands. Between March 2005 and March 2006 monthly samples of T. picturatus were collected randomly at the central fishery wharf from the commercial catches of purse-seiners in Tenerife Island waters (Canary Islands). Some 2472 specimens were analysed, with total lengths from 10.4 to 31.9 cm. Although females outnumbered males in summer, males were more abundant in the sex ratio (1.36 : 1). Based on the monthly evolution of the gonado-somatic index and the proportion of mature individuals, the spawning season occurred between January and April, peaking in February. Lengths at first maturity (LFM) were calculated from the maturity ogives by the Gompertz model for all specimens (22.79 cm), for males (21.20 cm) and for females (23.05 cm). In this area the minimum legal size for T. picturatus is actually smaller than the length at first maturity and should be revised to avoid depletion of the stock.

Atlantic cod Gadus morhua L. were fed high plant protein diets added to either shrimp-shell meal or crab-shell meal. The aims were to investigate if diluting dietary energy would reduce the liver index (HSI) and if marine ash would add value to plant protein-based diets. Two control diets were used: a high plant protein control diet (PP) with no marine ash addition, and a fishmeal-based diet (FM) with no marine ash addition. All diets were evaluated in small cod (initial weight 79 ± 15g) and in market-size cod (initial weight 1579 ± 20 g). Addition of crab-shell meal up to 20% and shrimp-shell meal up to 10% did not influence liver size in either small or market-size cod. An addition of up to 20% crab-shell meal and 10% shrimp-shell meal improved growth compared to the PP control diet, and stimulated increased feed intake. However, 10% shrimp-shell meal and 20% crab-shell meal diets resulted in a similar intake of energy and protein as the control groups. Increasing shrimp-shell meal to 20% resulted in reductions in feed intake, fat digestibility and growth, and in altered gut histology. All diets, except the 20% shrimp added diet, resulted in normal ranges of plasma nutrients and blood hematological values, showing good fish health with or without the marine ash addition.

An experimental approach was used to analyze preferences of the burbot (Lota lota) with regard to water depth, substrate type and flow velocity. In total, 30 burbots used in the experiments were caught in the middle reaches of the River Elbe by electro-fishing. Immediately after capture, they were placed in a 180 L transportation box with aerated freshwater and taken to the research aquarium of the Zoological Museum Hamburg where they were divided into two groups according to total length: group I, 10.0–16.5 cm; group II, 20.0–30.0 cm. Prior to the experiments the fish were adapted to laboratory conditions for four weeks at 20°C in four tanks, each containing 720 L water. For each experiment, three L. lota were transferred to an additional 1350 L experimental tank. After a one-day adaptation phase each experiment ran for three continuous day and night phases. Burbot preferences were tested for (i) water depth, (ii) substrate size, (iii) water depth and substrate size combined, and (iv) water depth, substrate and flow velocity in combination. Diurnal and nocturnal activities were recorded and analyzed throughout all experiments. Burbots of both length groups showed a significant preference for deeper water depths and large cobble substrate. Substrate type was found to be the dominant factor determining habitat preferences of L. lota when investigated in combination with water depth. In experiments combined with flow velocity, substrate and water depth were the most important factors determining burbot habitat preferences, and flow velocity of minor importance. In general, burbots were most active at night, while daytime activity was much lower. However, in all experimental approaches in the smaller length group the burbots displayed much higher day- and night-time activity than did the individuals in the larger length group.

Piscivory of perch can occur within a few weeks after perch hatch, leading to the development of two size-cohorts, with the larger perch becoming cannibals. However, the possibility of early piscivory is assumed to depend on the hatch timing of the prey and predator. Two species, bream (2006) and roach (2007), were tested as the prey fish. The bream (hatching 12 days after perch) were preyed upon by the perch, leading to the predicted development of two sizes of cohorts as well as to cannibalism. With roach (hatching simultaneously with perch), however, no piscivory or cannibalism occurred and the perch population was unimodally distributed. The results of this experimental pond study underpin recent theoretical findings that size differences between predator and prey, determined through differences in the timing of hatching as well as differences in juvenile growth rates, foster the occurrence of early piscivory in YOY perch that may lead to bimodality and finally to intra-cohort cannibalism.

The length-weight relationship (LWR) was used to test differences in the fish somatic condition factor among four populations of the endangered desert pupfish, Cyprinodon macularius, from the Lower Colorado River Basin, Mexico. Bimonthly fish sampling and habitat assessments were carried out from September 1996 to August 1997 for four sites in Baja California and Sonora. Slope b of the WLR varied from 3.238 (Cerro Prieto population) to 3.613 (Welton-Mohawk population), showing in all populations a positive allometric growth. Male b values were higher than those of females for Cerro Prieto (3.303 vs 3.071), Welton-Mohawk (3.866 vs 3.579), and Flor del Desierto (3.357 vs 3.169) populations. The Cerro Prieto population showed the highest somatic condition (y-intercept, a = −11.759). Water depth and salinity were the ecological variables that better accounted for most of the variation in the somatic condition of this pupfish, with a negative and a positive effect, respectively.

To investigate the effect of Coriolus versicolor polysaccharides (CVPS) on the immune response of crucian carp (Corassius auratus gibelio), fish were fed diets containing CVPS at different concentrations including 0.5, 1.0 and 2.0 g kg⁻¹ for 5 weeks. Other groups of fish were vaccinated by intraperitoneal injection (i.p.) against Aeromonas hydrophila with a killed bacterin at the beginning of the experiment and fed the same diets as described above. Additionally, control fish and vaccinated-only fish were fed basal diets without CVPS supplementation. The phagocytosis, lysozyme activity, complement components C3 and C4, E-C3bRR (Erythrocyte-C3b rosette rate) and E-CIRR (Erythrocyte-immune complex rosette rate) levels and circulating antibody titers in the serum were monitored. Five weeks after feeding the prescribed diet, fish were challenged with A. hydrophila and the mortalities recorded. Results showed that feeding non-vaccinated and vaccinated crucian carp with CVPS stimulated the phagocytosis of leukocytes, lysozyme, complement components C3 and C4, erythrocyte immune adherence, and circulatory antibody titers in serum in vaccinated crucian carp. Immune parameters increased to their highest levels after 3 weeks of feeding the diet containing 0.5 or 1.0 g kg⁻¹ CVPS. These doses also resulted in the highest protection in the challenge experiment. Best survival (85%) was in the vaccinated group fed the diet containing 1.0 g kg⁻¹ CVPS, whereas almost 80% of control fish (negative control) and 50% of vaccinated-only fish (positive control) died.

Experimental trawl surveys in Izmir Bay (Aegean Sea) were taken seasonally between 2007 and 2009. A total of 1353 specimens were sampled ranging from 5.9 cm (1.4 g) to 44.4 cm (670 g). The main size group of Merluccius merluccius was between 14 and 25 cm total length (TL). In total, the mean catch per unit effort (CPUE) for hake by number and weight was 101.4 ± 18.4 ind h⁻¹ and 10.7 ± 1.5 kg h⁻¹, respectively. Highest mean CPUE by number and biomass was determined as 257.1 ± 15.1 ind h⁻¹ and 15.1 ± 4.9 kg h⁻¹ in summer. Mortality (M, F, Z) ratios of hake were 0.58 year⁻¹, 1.66 year⁻¹ and 2.24 year⁻¹, respectively. Because of the many smaller specimens caught in this study, this seems to indicate that there may be heavy fishing pressures on the hake population; the high exploitation rate (E = 0.74) appears to confirm this conclusion.

Histological and ultrastructural analyses of gills were observed in Nile tilapia collected from three different waterbodies in southeast Brazil: an urban lake in a park in the city of São Paulo, a reservoir in a rural city, and a commercial aquaculture facility. These waterbodies were analyzed and classified as hypereutrophic, eutrophic, and supereutrophic, respectively, with 310.00, 94.00, 28.00 of phosphate ( μg L⁻¹) and 65.49, 24.95, 12.83 of chlorophyll (μg L⁻¹). A significant difference in the histological alterations index (HAI) was observed only in fish from the urban lake, with the presence of cell hypertrophy, hyperplasia, aneurism, and other alterations. When compared to the other groups, a large quantity of rodlet cells was also observed in the urban group. These results demonstrate the correlation of eutrophic states of water with gill morphology. Also discussed is the premise that large amounts of organic material dissolved in water can alter the morphology of the fish gills.

Age, growth, and mortality of the edible crab, Cancer pagurus, were determined for the native population in South Wales (UK). Sampling was carried out on a monthly basis between February 2001 and September 2002. Carapace width ranged between 10.4 and 163 mm. Based on the carapace width frequency distribution, the Swansea and Gower population was composed mainly of males belonging to the first and second age-class (1 and 2), and of females belonging to the third and fourth age-class (3 and 4). Sex ratio was 1.126 ± 0.27 in favour of males. Carapace width frequency distributions and weight-at-age data were used to estimate the von Bertalanffy growth equation parameters. For the population as a whole, these were: L∞ = 199 mm, W∞ = 1179.56 g, K = 0.24 year⁻¹, t₀ = −0.1004 years. The overall carapace width–weight relationship was: W = 0.38(CW^2.69). Analysis of covariance indicated a significant difference in the carapace width–weight relationship between males and females in the study area. Total mortality Z and natural mortality M rates for combined sexes were 1.245 year⁻¹ and 0.567 year⁻¹, respectively. The exploitation ratio E was estimated to be 54.43%.

The declining trend in the catches of santer seabream, Cheimerius nufar (Val. 1830), and sizable capture of immature and mature fish from the Arabian Sea at the coast of Oman have led to questioning the hypothesis that the fishery is in a state of decline due to inappropriate management. The lack of data on the basic biology and landing statistics for exploited fish species have made the management of fish resources in western Indian Ocean complicated. This paper presents data on the population biology of C. nufar in the Arabian Sea, with a view to contributing towards the development of management plans for a sustainable exploitation. A total of 4132 fish were obtained from the artisanal hand-line fishery catch at the Lakbi and Salalah landing sites from April 2005 to March 2007. Size distribution ranged from 16 to 64 cm [total length (TL)]. About 67.5% of the catch was composed of fish measuring <32 cm TL. Neither sex dominated the population nor were there significant differences in the monthly and annual sex-ratios tested by chi-squared. Spawning is from May to October. The declining trend in the hepatosomatic indice (HPI) values from September to February was almost identical to the declining trend in the gonado-somatic indice (GSI) values. The rise and fall in the condition factor (CF) values could not be related to the spawning period. Females and males mature at 31.9 and 33.7 cm TL, respectively. Otolith readings indicated the life span to be about 13 years. The instantaneous rate of natural mortality was estimated with M = 0.62 year⁻¹.

Over the past few decades, fish resources have declined severely owing to the river–lake disconnection within the Yangtze River floodplain. Studies on fish migrations between rivers and floodplain waters are imperative for fish resources restoration and lake management. However, few studies have as yet documented the migration rhythms of river–lake migratory fishes. Monthly investigations of the fish assemblage structure were conducted in three regions of the Dongting Lake, which is connected to the Yangtze River. Main results were: (i) Fish catches varied greatly, depending on the water level and area of the lake; (ii) Ten river–lake migratoty species were caught during the study, 80% of these during July–October when the water level was high. Species richness and relative abundance both decreased with increasing distance from the river, and the timing of peak abundance occurred later in the year; (iii) Abundance of grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) peaked in July and August and were mainly composed of 0 + fishes. The results revealed that the key time for migration into the lake is July–August. Combining the results from previous studies, a comprehensive view is given of migration patterns of four domestic Chinese carps; (iv) Brass gudgeon (Coreius heterodon), appeared to migrate into the Dongting Lake as two separate shoals, differentiated by body size. They also appeared to remain close to the lake mouth area. Based on the above results, two recommendations can be made for river–lake migratory fish conservation in the Yangtze floodplain: prolonging the current fishing ban period of April–June to April–September; and opening sluice gates for as long as possible during April–September in order to maximize the opportunities for fish migration.

An eight-week feeding trial was conducted to determine the dietary histidine requirement of Indian catfish, Heteropneustes fossilis (6.20 ± 1.25 cm, 4.65 ± 0.48 g) in 75-L flow-through circular troughs. Six isonitrogenous (40%) and isoenergetic (17.90 kJ g⁻¹) amino acid test diets with graded levels of l-histidine (0.25–0.75%, dry diet), in gradation of 0.10% histidine were formulated. Fish were randomly stocked in triplicate groups and fed experimental diets at 4% BW per day at 08:00 and 18:00 h. Maximum live weight gain (288%), best FCR (1.40) and PER (1.78) were occurred at 0.55% dietary histidine level. For the live weight gain, FCR, PER and body protein deposition data were examined using quadratic regression analysis, the breakpoints indicating requirements for histidine at 0.58, 0.54, 0.53 and 0.54% of dry diet, respectively. Significantly (P < 0.05) low moisture and higher whole body protein content were obtained in the 0.55% histidine diet, while body fat showed an increasing trend with the increase in dietary concentrations. Ash content remained insignificantly (P > 0.05) low among all dietary groups, except in diet I and diet II. Based on the above results, the recommended diet for young H. fossilis should contain histidine at 0.54% of dry diet, corresponding to 1.35% of dietary protein for optimum growth and efficient feed utilization.

One of the main concerns of shrimp fisheries is the associated impact on ecosystem biodiversity, particularly on fish assemblages that are poorly characterized yet likely very relevant to the health of the ecosystem. The continental shelf along the eastern coast of the mouth of the Gulf of California is a region of high biodiversity that harbors highly productive fisheries. This study aimed to analyze the changes in the soft bottom fish assemblages caught as bycatch in the shrimp fishery located in this region. Sampling was conducted with commercial trawls at 16 fixed stations during the 2006–2007 shrimp-fishing season. A total of 103 fish species from 80 genera and 47 families were collected. The ecological and taxonomic diversity as well as the composition and abundance of the fish community caught as bycatch in the shrimp trawl fishery were found to be significantly different in the autumn and winter. Ordination and similarity analyses also revealed differing patterns. Species abundance was strongly associated with sea bottom temperature, depth and latitude. The effects of these abiotic variables on the observed diversity patterns and the possible influences of the fishery are discussed.

Pre-spawning water level increase (PWLI) is a recently discovered parameter of water level dynamics affecting juvenile year-class strength (YCS) in shallow-water-spawning fish. By analysing a time series of commercial common bream (Abramis brama) yields in Lake Constance from 1950 through 2007, this study showed that the differences in juvenile YCS are conserved until the adult life stage. Adult YCS was best explained by complex interactions of PWLI with both stock-intrinsic and extrinsic environmental variables. The correlation between PWLI and YCS of adult bream became more pronounced as the trophic state of the lake increased. It is argued that this mediator effect of the trophic state results from increased growth of the algal biofilms during high trophic state periods. These biofilms are known to impair safe attachment of the eggs to the substratum and affect mortality rates of the eggs. Furthermore, reproductive stock size exhibited a positive effect on the resulting YCS. However, a marginally significant interaction between reproductive stock size and PWLI indicates that the two positive effects of PWLI and reproductive stock size on YCS were not fully additive, probably because the very large year-classes resulting from the combined positive effects suffered from strong intra-specific competition. This study demonstrates that anthropogenic water level regulation, e.g. for flood protection or for the generation of hydroelectric power, and climate change altering PWLI have the potential to affect YCS throughout the whole life cycle of bream, particularly in eutrophic water bodies. Similar effects of PWLI are anticipated in other shallow water spawning species.

It is important to understand parental effects on early life history of fish as manifested, for example, in individual fitness of offspring. Immediately after fertilization, parental contributions (both genetic and non-genetic) to embryos will affect larval ontogeny, physiology, morphology and survival. In marine fish, rates of natural mortality are highest during early life and are negatively correlated with rates of growth and body size. In these early life stages (eggs, larvae, young juveniles) subtle differences in mortality can cause large differences in recruitment and year-class success. Therefore, it is particularly critical to understand factors that contribute to variability in mortality during early life. This study focuses on evaluating the potential influence of paternity on rates of mortality and development in eggs and larvae of Northwest Atlantic cod, Gadus morhua. To accomplish this 12 males and two females were crossed using a full-factorial breeding design. Paternity had a strong influence on fertilization success, hatching success, cumulative embryonic mortality, larval standard length, eye diameter, yolk-sac area, and cumulative larval mortality. Female 1 showed an overall ‘weaker’ performance of offspring than Female 2, indicating that deviances can stem from differences in female quality. Nevertheless, paternal contributions to embryonic and larval development were still evident despite differences in female quality, showing that sire effects on offspring are undeniable and can serve as important sources of variation during early life stages in fishes. Overall, these findings have implications for furthering the understanding of recruitment variability and can be used to optimize reproductive output for the aquaculture industry. In addition, the data suggests that the choice of mate during spawning can play a large role in offspring fitness.

The aim of this study was to assess plasma biochemistry parameters with the potential of being used as indicators of the nutritional status for healthy gilthead seabream juveniles. Triplicate groups of 18 seabream (body weight of 58 g) were kept unfed for 24 h, 7 or 14 days. Nine fish per treatment were then sampled randomly for blood collection and the following parameters analyzed in the plasma using standard clinical methods: glucose; protein; triglycerides; cholesterol; calcium; magnesium; inorganic phosphorus; alkaline phosphatase (ALP); aspartate aminotransferase (AST); lactate dehydrogenase (LDH); gamma-glutamyl transferase (GGT); creatine phosphokinase (CPK); and lipase. Biochemical parameters showed lower variability among individuals than did enzymatic parameters. Plasma glucose, protein, cholesterol, calcium and inorganic phosphorus levels were inversely related to the duration of starvation. On the contrary, plasma triglycerides decreased significantly during the first week of starvation and remained stable in the second week. Plasma ALP, AST and LDH decreased significantly after 1 week of starvation and then remained constant. In healthy seabream juveniles, plasma glucose, protein, cholesterol, calcium and inorganic phosphorus are responsive to starvation and may be useful indicators of the nutritional status of the animals. Indicative baseline reference values for gilthead seabream juveniles starved for 24 h and held at optimum temperature are: protein, 3.7–4.9 g dl⁻¹; cholesterol, 341–407 mg dl⁻¹; calcium, 13.1–8.0 mg dl⁻¹; and inorganic phosphorus, 10–14.2 mg dl⁻¹. Plasma triglycerides, along with plasma enzyme activities, may be useful as indicators of short term starvation. For these parameters baseline values after 1 week of starvation were: triglycerides: 138–230 mg dl⁻¹; ALP: 58–125 U L⁻¹; AST: 15–127 U L⁻¹; and LDH 61–677 U L⁻¹. Plasma glucose is only responsive to longer starvation periods, remaining relatively stable during the first week of starvation, and ranging from 59 to 196 mg dl⁻¹.

The present study was undertaken with the objective to investigate the intraspecific variation of Channa punctatus on the basis of morphometric characters using the truss network system that was constructed from the fish body. Fish samples were collected from the Narora (n = 62) and Kanpur sites (n = 46) of the Ganga River, the Firozabad site in the Yamuna River (n = 66) and at the Lucknow site of the Gomti River (n = 60). Data were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. The first principal component (PC I) analysis explained 47.75% of total variation while PC II and PC III explained 8.18 and 7.48%, respectively. The step-wise discriminant function analysis retained seven variables that significantly discriminated the populations. Using these variables 81.85% of the original groups were classified into their correct samples. Misclassification was higher for the samples from Ganga River (19.6% at the Kanpur site and 19.4% for the Narora site). Of the total 27 transformed morphometric measurements, 23 exhibited significant differences among the populations. These findings indicate the presence of different stocks of fish from the three rivers.

Fish hybrids provide genetically manipulated products of excellent value for the commercial aquaculture industry. However, if handled or marketed incorrectly, they can cause great financial loss to producers as well as threaten the native species. Herein, molecular markers are established to identify hybrid lineages of pimelodids and characterize them in relation to their parental species, Pseudoplatystoma corruscans, Pseudoplatystoma reticulatum, Phractocephalus hemioliopterus and Leiarius marmoratus. The results show that the mitochondrial genes are useful for identification of the cross-direction through the characterization of the maternal lineage. The nuclear genes allow identification of the interspecific hybrids. Use of genetic markers can avoid misidentification of hybrids that occur in simple morphological analysis. Thus, the present results allow the routine monitoring of pimelodid hybrids for their correct management and trade in aquaculture.

Temperature is considered an important factor that influences the life cycle of annual fishes, however the thermal preferendum of Austrolebias nigrofasciatus reproduction has not been defined. The hypothesis was that the fecundity of the species would respond differently within the temperature range analyzed, presenting an optimum thermal. Thus, this study investigated the effect of temperature on the fecundity of A. nigrofasciatus for the first time under laboratory conditions. Pairs of A. nigrofasciatus were placed in aquaria with temperatures of 17, 21 or 25°C, with four pairs (replicates) for each treatment, for five weeks. Contrary to expected, there were no significant differences in fecundity parameters among the tested temperatures, but the weekly fecundity at 17 and 21°C was more homogeneous than at 25°C. During the experimental period, the temperature did not affect male growth; however, at 25°C there was a negative effect on female body growth. The condition factor was also influenced, suggesting a tendency towards a negative energy balance with increasing temperature. The results indicate that temperatures between 17 and 21°C are suitable for broodstock maintenance.

The present study was carried out to investigate the carcass traits of farmed freshwater Labeo rohita in relation to body size as important information to calculate yield and/or support for machine/manual processing. For this purpose ninety specimens were collected for nine weight groups from 600 to 1100 g, each group with a 100 g increment. Specimens were collected from grow-out culture ponds of the Central Institute of Freshwater Aquaculture (CIFA), Bhubaneswar. The carcass evaluation technique was followed to evaluate carcass yield, offal yield and carcass cutability. Head size percentage of rohu increased as the body mass increased, which in turn increased the processing yield. Dry matter and ether extract percentage also increased with the body mass; however, moisture percentage showed a decreasing trend. The fore cut showed a distinctly higher ether extract percentage followed by the middle and posterior cuts. There was a good correlation development to describe the relationship between yield traits and body weight.

Length–weight relationship parameters (a and b) are presented for three fish species in the Beimen lagoon, Taiwan.

This study presents length-weight relationships for nine neotropical fish species collected from four shallow lakes from the southeastern Pampean region, representing the first record for these species. Also, new sizes for six species are also provided.

Length–weight (LWR) relationships were estimated for nine fish species collected in the Wujiang River located near the city of Chongqing, China. The value of the exponent ‘b’ in the LWR was between 2.594 and 3.528, which shows that the species exhibit an allometric growth pattern. All relationships between total length (TL) and body weight (BW) were linear (in all cases: r² > 0.913).

This study presents the first references available for length–weight relationships (LWRs) of ten endemic fish species: Oxynoemacheilus eregliensis (Banarescu & Nalbant, 1978), Seminemacheilus lendlii (Hankó, 1925), Cobitis turcica Hankó, 1925, Capoeta antalyensis (Battalgil, 1943), Capoeta caelestis Schöter, Özulug & Freyhof, 2009, Capoeta pestai (Pietschmann, 1933), Gobio gymnostethus Ladiges 1960, Gobio hettitorum Ladiges, 1960, Pseudophoxinus antalyae Bogutskaya, 1992 and Scardinius elmaliensis Bogutskaya, 1997 from the inland water systems of Turkey.

This study describes the length–weight relationship (LWR) of Pseudophoxinus alii from the Yamansaz Lake, a coastal freshwater lake in Antalya, Turkey. A total of 105 specimens were obtained using a variety of nets between April 2007 and March 2008. Total lengths ranged from 3.4 to 14.3 cm. The length–weight relationship showed a positive allometric growth (b = 3.012; R² = 0.988). The study presents the first reference on LWR for this threatened species. The results also indicate a new maximum total length not previously reported in the international literature.