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Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Acknowledgements
  7. References

This study presents length-weight relationships (LWR) for 19 species captured in the Jacuí Delta in southern Brazil. Most of the species had no previous LWR estimates.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Acknowledgements
  7. References

Growth parameter estimates of fish species are of fundamental importance for the management of fisheries and understanding of the population biology. LWRs allow comparisons between and among populations based on the growth performance.

The objective of this study was to provide LWRs for 19 species occurring in the Jacuí delta area in southern Brazil.

Materials and methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Acknowledgements
  7. References

The study area comprises a region of the Delta State Park Jacuí (PEDJ) (29°58′31″S; 51°15′53″W), a component of the Guaiba hydrographic region near the metropolitan region of Porto Alegre, RS, Brazil. The PEDJ is an Environmentally Protection Area consisting of numerous islands, channels and wetlands.

The specimens were collected in monthly sampling from June 2008 to May 2009 using electrofishing and gill nets. The nets were set for 12 h at night in the pelagial and in the shallow margin areas.

Collected specimens were fixed in 10% formalin. After identification at species level, the total length was measured to the nearest mm and each individual weighed to the nearest gram. Species identification was based on Reis et al. (2003).

LWR parameters (a and b) were estimated by linear regression, expressed by the equation log W = a + b * log L, where: W = weight in grams, L = total length in centimetre, a = intercept and b = slope of the regression line (Froese, 2006).

In species with r² <0.95, the outliers were identified and removed by using log a vs b plots (Froese, 2000), and the regressions recalculated.

Results and discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Acknowledgements
  7. References

The total capture was 2380 individuals belonging to 19 species and 12 families from four orders of the class Actinopterygii. The species and number of individuals captured, biometric data, LWR parameters (a and b), and the coefficient of determination (r²) are given in Table 1.

Table 1. Length-weight parameters for Jacuí Delta species, southern Brazil.
OrderFamílySpeciesNTotal length (cm)Total weight (g)LWR parameters
MinMaxMinMaxlog a95% IC of ab95% IC of br²
  1. Numbers in bold = new maximum lengths (Froese and Pauly, 2013).

CharaciformesAcestrorhynchidaeAcestrorhynchus pantaneiro 6419.330.957.4282.10.00140.0006–0.00313.583.32–3.850.92
Anostomidae Schizodon jacuiensis 1615.1 34.8 28.7507.60.00350.0020–0.00593.343.18–3.500.99
Characidae Astyanax eigenmanniorum 955.9 14.4 336.30.01860.0121–0.02132.872.75–3.000.95
Astyanax jacuhiensis 552.511.11.218.20.01260.0088–0.01723.072.90–3.240.96
Hyphessobrycon luetkenii 1413 9.6 0.312.40.01260.0102–0.01533.062.94–3.190.95
Oligosarcus jenynsii 1406.622.52136.50.00630.0043–0.00893.193.06–3.320.95
Oligosarcus robustus 452.8 31.3 0.19307.50.00600.0048–0.00733.143.06–3.210.99
Crenuchidae Characidium zebra 153.15.80.231.40.00680.0038–0.01163.112.73–3.480.96
Curimatidae Cyphocharax voga 8894.2 24.8 1.12870.01120.0103–0.01193.103.07–3.120.99
Erythrinidae Hoplias malabaricus 577.345.54.113500.00830.0060–0.01153.092.99–3.190.99
ClupeiformesEngraulidae Lycengraulis grossidens 167.522.82.478.30.00950.0055–0.01612.812.62–3.010.99
PerciformesCichlidae Australoheros facetus 184.915.52.792.10.01860.0141–0.02433.092.97–3.210.99
Crenicichla lepidota 435.420.91.5126.50.00850.0069–0.01023.133.05–3.210.99
Geophagus brasiliensis 86322.30.43228.70.01620.0131–0.019363.083.00–3.160.99
Sciaenidae Pachyurus bonariensis 15510.9 24.6 11.2150.50.00390.0029–0.00523.363.26–3.460.96
SiluriformesCallichthydae Hoplosternum littorale 6912.2 25.4 30.5185.50.01350.0085–0.02063.122.97–3.270.96
Loricariidae Loricariichthys anus 1211432.512.4180.90.00180.0012–0.00253.303.19–3.420.96
Pimelodidae  Parapimelodus nigribarbis 11610.8 19.8 6.855.10.01020.0061–0.01662.822.63–3.020.88
Pimelodus maculatus 2009.429.537.82330.00910.0058–0.01383.002.86–3.140.90

When comparing LWR estimates of the present study with previously published values using the FishBase online log a vs b plot, most of the new LWR values fell within the ellipse. Species such as Hoplias malabaricus, Lycengraulis grossidens, Hoplosternum littorale and Pimelodus maculatus that have several published estimates, show values within or near the confidence limits of the present study. LWR estimates of Oligosarcus jenynsii, Cyphocharax voga, Australoheros facetus and Pachyurus bonariensis published in former studies fell beyond the confidence intervals of the present study, probably due to the low number of samples.

Acknowledgements

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Acknowledgements
  7. References

The authors thank the colleagues of the Laboratory of Fish Ecology, UNISINOS, for their assistance during the fieldwork.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results and discussion
  6. Acknowledgements
  7. References
  • Froese, R., 2006: Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations. J. Appl. Ichthyol. 22, 241253.
  • Froese, R., 2000: Evaluating length-weight relationships. In: FishBase 2000: concepts, design and data sources. R. Froese and D. Pauly (Eds). ICLARM, Los Baños, pp. 133.
  • Froese, R.; Pauly, D. (Eds), 2013: Fishbase, 2011. World Wide Web electronic publication. Available at: www.fishbase.org, version (06/2013) (accessed on 20 July 2013).
  • Reis, R. E.; Kullander, S. O.; Ferraris, C. J. Jr, 2003: Checklist of the freshwater fishes of South and Central America. EDIPUCRS, Porto Alegre, pp. 742.