INSTITUTO DE LIMNOLOGIA "DR. RAUL A. RINGUELET"
Unidad Ejecutora - UE
Effects of stocking density and natural food availability on the extensive cage culture of pejerrey (Odontesthes bonariensis) in a shallow Pampean lake in Argentina
GARCIA DE SOUZA, J. R.; SOLIMANO, P.; MAIZTEGUI, T.; BAIGÚN, C. R. M.; COLAUTTI, D. C.
WILEY-BLACKWELL PUBLISHING, INC
Lugar: Londres; Año: 2015 vol. 46 p. 1332 - 1332
An experiment was conducted for 80 days at La Salada de Monasterio Lake (Buenos Aires, Argentina) to assess the effect of stocking density and natural food availability on thegrowth and production of juveniles of pejerrey (Odontesthes bonariensis) in extensive cage culture. Ten cages were installed and stocked with 33-day-old fish, at three density treatments: 25, 50 and 75 ind.m-313. The zooplankton was sampled fortnightly and analysed in terms of abundance, biomass, and species composition considering three size classes. Caged pejerrey were sampled and measured in length and weight, and its diet was assessed regularly. The zooplankton was always dominated by the smaller size individuals, and nonetheless, the pejerrey gut contents composition was clearly different from cage zooplankton, showing a trend to contain the bigger components of zooplankton. Reared fish exhibited a tendency to diversification of the diet and to change the mean prey size depending on fish length and stocking density. A selective utilisation of the resources by juvenile pejerrey is evidenced by regression models showing a positive and direct effect of the bigger zooplankton biomass on fish growth rates, which were also inversely affected by the availability of the smaller zooplankton, highlighting the importance of zooplankton quality. The fish grew more in length and weight at lower stocking densities, the maximum fish number was obtained at maximumdensity and the final maximum fish biomass was seen at intermediate stocking density. The results demonstrate that stocking density and available zooplankton, in both quantity and quality, are key factors in regulating extensive cage culture of pejerrey. Testing the referred variables and the digestive contents, it is possible to optimise the efficiency of the system handling stocking densities in a dynamic way, regarding the zooplankton and fish diet features.