Aquaculture, the rearing of aquatic organisms under controlled or semi-controlled conditions to produce organisms, mainly for food, ornamental and sporting purposes, is a fastest-growing animal-food-producing sector in the world. The human-mediated introduction of exotic fish has played an important role in the success story of aquaculture. Nonetheless, many exotic fish have been implicated in the loss of native fish biodiversity, largely through the transmission of parasites and diseases amongst others. Whilst the transmission of parasites following the introduction of exotic food fish is well documented, transfer of those carried by exotic ornamental fish has received little attention. This article provides the first summary review of the global translocation of the platyhelminthes class Monogenoidea via the aquarium fish trade to draw attention to the growing parasitological risk factors associated with this form of commerce. By examining the invasive characteristics of both aquarium fish and monogenoids, I review how the monogenoids fit into the different stages that an introduced species goes through when invading the destination environment. For this, I use a theoretical framework, synthesising published reports on the aquarium fish trade with current knowledge on monogenoids to model invasion success. Next, I provide examples of invasive monogenoids on exotic Indian aquarium fish and briefly discuss the vulnerability of India to colonisation by imported aquarium fish and their parasitic monogenoids. I conclude that the aquarium fish trade is a perfect gateway for worldwide translocation of monogenoids. As this trade continues to increase and intensify, global translocation of monogenoids will expand even further.

Knowledge on the importance of associations between bacteria and microalgae in aquatic ecosystems is rather limited at the moment, mostly due to a lack of studies at the molecular and biochemical level of microorganisms. This paper discusses the current knowledge on microalgae–bacteria interactions and their potential impacts on the productivity, efficiency and sustainability of aquaculture. Current findings suggest that the interactions are complex and specific. The release of stimulatory products by bacteria that enhance the growth of microalgae, and vice versa, indicates the existence of mutualistic relations. Other factors, such as signalling between bacteria and microalgae, may also play an important role. Although these interactions may be of significant importance, to date, only a few findings have been reported on the use of consortia consisting of microalgae and bacteria for practical purposes. Interestingly, these results pointed out that a combination of microalgae and bacteria is often better than using either of them alone. Further research is needed to obtain a thorough understanding of the mechanisms behind the interactions between these microorganisms, including the identification of active compounds. This knowledge will enable the selection of appropriate consortia for different applications in aquaculture, including disease control and high and sustainable production of feed.

Because of health and environmental concerns, the use of chemotherapeutic agents has been restricted in many countries over recent years. This restriction has resulted in a demand for alternative strategies to improve aquaculture production and enhance disease resistance. Among these options, probiotics, live micro-organisms that confer a health benefit to the host by providing both a nutritional benefit and protection against pathogens, represent an important option for the management of diseases and their use may replace some of the therapeutic chemicals commonly used in aquaculture. Our review explores the current state of knowledge on the impacts of probiotics on aquaculture, with particular emphasis on the criteria used for selection and evidence of their beneficial effects.

Early gonadal development in Russian (Acipenser gueldenstaedtii Brandt, 1869) and Siberian sturgeon (Acipenser baerii Brandt & Ratzeburg, 1833) reared in controlled conditions from dph 1–439 (days post hatching) was studied using histological methods. Migrating primordial germ cells (PGCs) were observed in both species on dph 1. On dph 25 in both species gonad primordia developed in gonadal ridges. In dph 115 juveniles two types of gonad were distinguished, putative ovary and putative testicle. Meiotic activity was observed in ovaries on dph 197, while in testicles the first meiotic divisions were observed much later, on dph 439 and only in several Siberian specimens. The presence of Vasa protein was confirmed exclusively in germ cells during gonadogenesis, indicating that Vasa is a good marker of germinal cells also in Acipenseridae. Vasa protein displayed a nuage association or nuage-like localization. Some differences in the level of Vasa protein expression during male and female gonad development were also observed. In the gonads of both investigated sturgeon species the PCNA (proliferating cell nuclear antigen)-positive reaction was observed first in oogonia, while in spermatogonia at approximately 115 dph which was correlated with active mitotic divisions of germ cells. Surprisingly, meiotic oocytes arrested in diplotene also demonstrated strong PCNA-positive germinal vesicle.

Although aquaculture continues to be the fastest-growing food-producing industry worldwide, the sector faces important challenges with respect to controlling infectious diseases. Indeed, the frequent use of antibiotics, which are traditionally the most important line of defence against bacterial disease, has raised problems related to the development and spread of resistance. As a result, we currently are in a race to develop novel therapeutics that should allow us to continue controlling bacterial disease in the future. In this respect, scientific progress of the past years has allowed us to start understanding the mechanisms by which bacterial pathogens are causing disease. This knowledge in its turn opens up novel possibilities to combat infections by interfering with these mechanisms, a strategy that has been termed antivirulence therapy. In this review, the current knowledge with respect to pathogenicity mechanisms of bacterial aquaculture pathogens is discussed, including adhesion mechanisms, production of extracellular polysaccharides and biofilm formation, production of lytic enzymes (e.g. haemolysins and proteases), mechanisms of iron acquisition, secretion systems and regulatory mechanisms such as quorum sensing and host–pathogen signalling with catecholamine stress hormones. Furthermore, an overview is given of the first steps towards antivirulence therapy for aquaculture, with a focus on quorum sensing disruption as a proof of concept.

The natural productivity of semi-intensively managed shrimp ponds is frequently represented by a diverse trophic structure that forms part of the diet of farmed organisms. As in natural ecosystems, these dietary components exhibit differing isotopic signatures that vary with diet and trophic level. These isotopic differences can be used to infer the transfer of nutrients, as the isotopic values of prey items and consumers can be integrated in mass-balance mixing models, allowing the quantification of the relative contribution of multiple nutritional sources to the growth of a specific organism. By applying such methodology, it has been possible to estimate the relative dietary contribution of several elements that belong either to the biota of the farming environment or that are part of formulated diets. Careful sampling methods and isotopic analysis of these samples provide valuable information, not only in terms of what the consumer organism has selected, captured and ingested, but also in terms of the proportions of assimilated nutrients in the consumer's tissues. Results from several studies indicate that the natural productivity found in semi-intensively managed ponds frequently supplies higher proportions of dietary carbon and nitrogen to shrimp growth than the formulated feed, emphasizing the nutritional relevance of the former. A synthesis of field and laboratory studies applying isotopic techniques to determine the relative contribution of nutrients derived from different biota elements and formulated feeds to the growth of farmed shrimp is presented.

Indonesia has a long history of aquaculture, dating from the 15th century. Subsequently, the country has become a significant contributor to global aquaculture production, destined for both international and domestic markets. In 2009 the Government of Indonesia announced its vision to see Indonesia become the highest (volume) producer of aquaculture products in the world by 2015, with production targets equivalent to an overall increase in production of 353% between 2009 and 2014. This paper comprises a PEEST (policy, economic, environmental, social, technical) review undertaken as a background study for a SWOT (strengths, weaknesses, opportunities, threats) analysis, the outcomes of the SWOT analysis and a discussion of possible approaches to support sustainable aquaculture development in Indonesia. To meet the vision of a dramatic expansion of aquaculture production, one or more of the following strategies is required: intensification and production segmentation, areal expansion, and/or production diversification. Most likely the continued development of aquaculture in Indonesia will be a combination of these three strategies, with the relative influence of each depending on production sector and market demands. A key issue identified in the PEEST review and SWOT analysis is the dominance (in terms of number) of Indonesian aquaculture by smallholder aquaculture farmers. We argue that a range of influences, including aquaculture production expansion and changing international market requirements, have the potential to negatively impact smallholder aquaculture farmers in Indonesia, and that further policy development should specifically address these issues.

Farming freshwater prawns with fish in rice fields is widespread in the coastal region of southwest Bangladesh because of favourable resources and ecological conditions. This article provides an overview of an ecosystem-based approach to integrated prawn–fish–rice farming in southwest Bangladesh. The practice of prawn and fish farming in rice fields is a form of integrated aquaculture–agriculture, which provides a wide range of social, economic and environmental benefits. Integrated prawn–fish–rice farming plays an important role in the economy of Bangladesh, earning foreign exchange and increasing food production. However, this unique farming system in coastal Bangladesh is particularly vulnerable to climate change. We suggest that community-based adaptation strategies must be developed to cope with the challenges. We propose that integrated prawn–fish–rice farming could be relocated from the coastal region to less vulnerable inland areas, but caution that this will require appropriate adaptation strategies and an enabling institutional environment.

There is a constant need to increase productivity in aquaculture, particularly to improve growth rate, feed utilization as well as stress resistance of fish. Because of consumer concerns and strict regulations in many countries, the use of synthetic chemicals, hormones and antibiotics is becoming unviable and natural compounds are more acceptable to the public. A wide variety of chemical compounds are found in plants, and many of them have been shown to have beneficial effects on appetite, growth and the immune status of fish acting through different mechanisms. Phytochemicals contained in herbs may enhance the innate immune system, possess antimicrobial capabilities, and are redox active molecules with antioxidant characteristics that may help to improve the general physiological condition of fish. Many studies have discussed the values of phytochemicals as feed additives. Another paramount concern related to phytochemicals is their endocrine modulator effect that can be applied both in aquaculture targeting the production of table fish and the growing sector of ornamental fish production. Different mechanisms such as the effects at the steroid receptor level, effects on steroid synthesis, distribution and excretion, actions on the hypothalamus–pituitary–gonad axis, as well as indirect mechanisms including thyroid and growth hormone disruption have been postulated for the reproductive endocrine disruption in fish populations by phytochemicals. This paper reviews the results of a great number of studies focusing on phytochemicals such as essential oils, saponins, flavonoids and phytosterols discussing their effects on productive traits and the putative mechanism of action.

Based on the fact that farmed fish experience different environments, stocking densities and feeding regimes compared with wild fish, several techniques have been developed to discriminate the wild or farmed origin of fish. These techniques quantify differences between genetics, chemical characteristics, fatty acid compositions, trace elements, pollutants, stable isotopes, morphology and organoleptic characteristics. Gilthead sea bream and European sea bass are the most important marine fish in Mediterranean aquaculture and are highly appreciated by commercial and recreational fisheries. A total of 60 studies that used techniques to discriminate farmed from wild fish for sea bream and sea bass form the basis of this review. The most common technique used differences in the lipid and fatty acid composition of fish. Many of these studies dealt with food science and product quality, rather than tracing escapees. A wide range of identification tools is useful in determining the correct origin of captures and proper labelling of marketed fish. External appearance and morphometry are useful for rapid assessments and can be achieved with high accuracy and little cost, especially for sea bream. This makes these methods suitable for detecting large and recent escape events, applicable in fisheries studies, and for ensuring that wild and farmed fish are separated in the marketplace. Techniques using differences in chemical or genetic composition are more useful for environmental monitoring, as they have higher accuracy and can detect escapees long after the escape incident. Regulatory bodies should legislate protocols that describe the technique(s) that must be applied in specific circumstances.

In aquaculture, nutrient loading is defined as the difference between nutrients supplied with fertilizers and feed and nutrients harvested in the form of finfish, crustaceans, molluscs and seaweeds. On average, the production of finfish and crustaceans results in a net nutrient loading, while for the production of molluscs and seaweeds the nutrient loading is negative. In marine and brackish water aquaculture, on a global scale, more nutrients are extracted than added to the environment. However, in freshwater, more nutrients are loaded than extracted. In 2008, the global aquaculture production of finfish and crustaceans resulted in an environmental loading of 1.7 million metric tonnes of nitrogen (N) and 0.46 million metric tonnes of phosphorus (P). This nitrogen loading represents 0.9% of the human input to the N-cycle and 0.4% of the global N-cycle. For phosphorus, the loading from finfish and crustacean aquaculture represents 2.3% of the global annual fertilizer supply. With cage aquaculture, nutrients are directly discharged to the environment. Mitigation measures should be shared equally between all polluters involved. For land-based aquaculture, the development of water re-use systems is still in its infancy. Although still a minor contributor to global aquaculture production, recirculation technology shows that control and mitigation of pollution from aquaculture is possible. A 15–20 year goal should be to have all inland aquaculture operations applying water re-use and purification technology and generating useful (waste) outputs in addition to standard aquaculture products.

Several chemicals have been tested as growth promoters in aquaculture but they cannot be endorsed for commercial processes due to their residual effects in the body of prawns, lobsters and crabs. The concern over environmental hazard, human health and food safety have led to a search for alternative growth promoters significantly to improve the growth of crustaceans with no such effects. Neurohormones, regulatory signalling molecules of crustaceans that coordinate multiple developmental and physiological processes, are major determinants underlying phenotypic integration. Competitive inhibitors for the moult inhibiting hormone receptor are expected to have a direct growth promoting effect on crustaceans by direct involvement in interference with the receptor in the Y-organ, which can cause a surge the production of ecdysteroids. Competitive inhibitors therefore can be regarded as growth promoters in crustacean fishery in addition to various other benefits. This review emphasizes the manifold effects of moult inhibiting hormone, a most versatile animal hormone, with an emphasis on the target sites and competitive inhibition.

Tilapia is the second most farmed fish group worldwide and over the past decade has quadrupled in production, largely due to their many characteristics conducive to aquaculture conditions as well as to the high marketability and relatively stable market prices. To keep pace with this rapid expansion, tilapia aquaculture will rely increasingly on more sustainable practices, but this must not be at the expense of decreased productivity, increased cost or compromised product quality. Since feed constitutes the major operating cost of tilapia farming, understanding their nutritional requirements, factors that may influence these requirements and implementing the most appropriate feeding management strategy is essential for the continued sustainability and scalability of the global tilapia industry. This review addressed these concerns by providing an overview of published nutrient requirement data and offered practical recommendations to the nutrition and feeding management of farmed tilapia, from broodstock to finishing feeds. The first section of this review extensively discusses the dietary protein/amino acids, lipids/fatty acids, carbohydrates, vitamin and mineral requirements of tilapia. Alternatives to marine-based ingredients, which are used increasingly in tilapia feeds, are also discussed. This is followed by discussing practical feed management aspects at the commercial farm level including feed formulations, feed types and feeding rates/frequency throughout the culture cycle. Recent research indicating significant differences in nutrient requirements and utilization efficiencies of improved tilapia strains versus non-improved strains are highlighted. This review aims to provide a comprehensive overview of tilapia nutrition and thus contributes to the continued global expansion of tilapia farming and the demand for their products.

Global aquaculture has expanded rapidly to address the increasing demand for aquatic protein needs and an uncertain future for wild fisheries. To date, however, most farmed aquatic stocks are essentially wild and little is known about their genomes or the genes that affect important economic traits in culture. Biologists have recognized that recent technological advances including next generation sequencing (NGS) have opened up the possibility of generating genome wide sequence data sets rapidly from non-model organisms at a reasonable cost. In an era when virtually any study organism can ‘go genomic’, understanding gene function and genetic effects on expressed quantitative trait locus phenotypes will be fundamental to future knowledge development. Many factors can influence the individual growth rate in target species but of particular importance in agriculture and aquaculture will be the identification and characterization of the specific gene loci that contribute important phenotypic variation to growth because the information can be applied to speed up genetic improvement programmes and to increase productivity via marker-assisted selection (MAS). While currently there is only limited genomic information available for any crustacean species, a number of putative candidate genes have been identified or implicated in growth and muscle development in some species. In an effort to stimulate increased research on the identification of growth-related genes in crustacean species, here we review the available information on: (i) associations between genes and growth reported in crustaceans, (ii) growth-related genes involved with moulting, (iii) muscle development and degradation genes involved in moulting and (iv) correlations between DNA sequences that have confirmed growth trait effects in farmed animal species used in terrestrial agriculture and related sequences in crustacean species. The information in concert can provide a foundation for increasing the rate at which knowledge about key genes affecting growth traits in crustacean species is gained.

Chile is the second largest producer of farmed salmon in the world. After reaching a peak harvest of 631 000 tonnes in 2008, a severe sanitary and production crisis triggered a major legal and operational reorganization, and an imminent expansion of the industry into the Aysén Fjords System (AFS). This expansion has caused increasing national and international concern about its potential negative impact upon this pristine area, which holds a mosaic of unique ecosystems and three World Biosphere Reserves. This paper reviews and provides some upper bounds to potential impacts under two feasible production scenarios. It is concluded that severe but highly localized mid-term damage to the sea-floor bottom may affect up to 6200 ha. Although this surface area represents only 0.5% of the AFS, the high heterogeneity and limited scientific knowledge of local ecosystems increase the risks of damaging sensitive habitats, communities or populations. While additional inputs of up to 60 000 t of nitrogen and 8000 t of phosphorus can be predicted, the estimation of carrying capacities is a pendant and urgent task to be accomplished in this area. If current escape rates are not reduced, the average number of escaped salmon may exceed 4.4 million individuals each year, able to consume up to 6600 t of pelagic prey from local ecosystems. We recommend following a strict precautionary approach, not granting new farming leases until sufficient information about the risk and magnitude of these impacts is obtained and transformed into effective management actions.

The issue of sustainability of salmonid culture has been the focus of considerable media coverage and debate between environmental activists and aquaculture industry stakeholders, particularly regarding the use of ingredients derived from wild fisheries (fishmeal and fish oil) in salmonid feeds. This study attempts to summarize recent data and to calculate the conversion efficiency of feed resources by Canadian farmed salmon in order objectively to assess the sustainability of this industry in this regard. Using updated information regarding domestic aquafeeds this review reports advances that have been made in diet formulation, fish in–fish out (FIFO) and feed conversion ratios (FCR) and demonstrates that production efficiency of farmed salmonids has significantly improved over time due to continued innovations in the aquafeed sector. The results suggest that the Canadian salmon aquaculture industry efficiently converts wild fish resources into high-value fish products.

A bio-economic model was used to analyse the risks of intensive production of shrimp and to propose alternative schemes of risk management by controlling aeration, pond size, stocking density and duration of cultivation. The model was calibrated from databases of farm operations in the State of Nayarit, Mexico. Improving management allowed us to project an increase in the annual net revenue from $3900 to $26 600 ha⁻¹ and to improve the benefit–cost ratio from 1.14 to 1.55. Managing an early start of aeration, small-sized ponds, high stocking densities and long cultivation periods maximized economic outcomes. Operating a small farm (consisting of a single 2.5 ha pond) involves more risk than operating a large one (50 ha, consisting of 20 ponds of 2.5 ha each). Improving management also resulted in diminished risk, as indicated by increased values of return per unit risk from 0.14 to 0.21 or from 0.42 to 0.51 (depending on farm size). From sensitivity analysis, we concluded that small ponds are recommended for intensive production of Litopenaeus vannamei and that white spot disease is a major risk factor that can be partly controlled by managing dissolved oxygen levels and aeration.

Artificial foods have been proposed in aquaculture as a complement or substitute for live food and the quality has been evaluated by considering nutritional value, acceptability, digestibility and water stability, but because of the filter-feeding behaviour of larvae of the cultured shrimp and the diversity of food found in the market for larviculture, it is important to define the size of food ingested by the different larval stages until the postlarval stage where raptorial habits are more evident than the filter feeding lifestyle. Selectivity assays in the pink shrimp Farfantepenaeus duorarum larvae were made using polystyrene DVB particles with a diameter between 1 and 50 μm as food. A group of organisms between zoea I and postlarval I stages were put into the particle suspension for 15 min to let the particles be ingested. The particle distribution in the medium and the content of the gut of the animals were characterized with digital-image processing analysis. The results were compared using the Ivlev selectivity formula, which contrasts the frequency distribution of each particle size in the medium and in the gut of larvae. The results of selectivity were adjusted with a third-order polynomial regression to determine the optimum and the preferred size of the food for each larval stage. The optimum sizes of the food ingested for the different stages of F. duorarum were between 6.17 and 12.02 μm and the preferred were found to be between 2.68 and 18.65 μm.

As an alternative food source to wild fisheries, aquaculture shows a great potential to help meet the growing demand for seafood and animal protein. The expansion of aquaculture has been achieved partly by system intensification, which has drawn vast criticisms of aquaculture for its environmental, social and economic sustainability issues. Life cycle assessment (LCA) has become the leading tool for identifying key environmental impacts of seafood production systems. A LCA evaluates the sustainability of diverse aquaculture systems quantitatively from a cradle-to-grave perspective. It provides a scientific basis for analysing system improvement and the development of certification and eco-labelling criteria. Current efforts focus on integrating local ecological and socio-economic impacts into the LCA framework. A LCA can play an important role in informing decision makers in order to achieve more sustainable seafood production and consumption. This article reviews recent applications of LCA in aquaculture, compares the environmental performance of different aquaculture production systems, explores the potential of including biodiversity issues into LCA analysis and examines the potential of LCA in setting criteria for certification and eco-labelling.

The results of bioeconomic analysis informed by a survey of 80 small-scale mud crab farmers in Vietnam are presented in this paper. Mud crab farming in Vietnam is profitable, with net revenue being approximately 135 and 41 million VND/year (USD 7000–USD 2100 per year) in the central and southern regions, respectively. Profitability was significantly higher in the centre compared with the north, as almost three times the biomass is harvested in the centre compared with the south (in turn, due to higher aquaculture area and survival rates). The benefit–cost ratio (the ratio between total revenue and total costs) is 3.55 in the centre and 1.97 in the south. The crabs are fed almost exclusively on low-value finfish in the centre and the south. Feeding rates were found to be low, with 95% of biomass gain coming from natural feed in the environment rather than supplementary feeding by the farmer. If pellets are to be adopted widely by mud crab farmers, negative perceptions regarding the poor adaptability of mud crab to pellets (northern farmers only), relatively slow growth rates compared with low-value finfish and lack of availability of pellets need to be overcome.

Temperature is one of the most important physical factors influencing fish growth. Under optimal temperatures, food energy partitioned into fish growth can be maximized. However, when a marine carnivorous species is cultured in an environment where temperature falls outside the optimal range of a fish, growth will be affected. The nutrient–environment interaction is important for optimizing a fish’s nutritional requirements throughout the grow-out period. The most current global issue for the aquaculture industry is the inclusion of alternative ingredients into formulated diets to produce a sustainable seafood product. This requires the substitution of fish meal and fish oil with alternative ingredients from plant and terrestrial animal sources. This review discusses the changes in nutritional requirements (protein, lipid and energy) and physiology of some commonly cultured marine fishes as a consequence of seasonal changes in temperature during the grow-out period. This review also discusses the effects of replacing fish meal and fish oil with alternative protein and lipid sources on the nutritional–environmental interactions of fish performance at different temperatures.

A semantic model for overall welfare assessment of Atlantic salmon reared in sea cages is presented. The model, called SWIM 1.0, is designed to enable fish farmers to make a formal and standardized assessment of fish welfare using a set of selected welfare indicators. In order to cover all welfare relevant aspects from the animals’ point of view and to create a science-based tool we first identified the known welfare needs of Atlantic salmon in sea cages and searched the literature for feasible welfare indicators. The framework of semantic modelling was used to perform a structured literature review and an evaluation of each indicator. The selected indicators were water temperature, salinity, oxygen saturation, water current, stocking density, lighting, disturbance, daily mortality rate, appetite, sea lice infestation ratio, condition factor, emaciation state, vertebral deformation, maturation stage, smoltification state, fin condition and skin condition. Selection criteria for the indicators were that they should be practical and measureable on the farm, that each indicator could be divided into levels from good to poor welfare backed up by relevant scientific literature. To estimate each indicator’s relative impact on welfare, all the indicators were weighted based on their respective literature reviews and according to weighting factors defined as part of the semantic modelling framework. This was ultimately amalgamated into an overall model that calculates welfare indexes for salmon in sea cages. More importantly, the model identifies how each indicator contributes (negatively and positively) to the overall index and hence which welfare needs are compromised or fulfilled.