Résumé
Objetivo. Evaluar el efecto de diferentes presas vivas en la larvicultura de bagre blanco (Sorubim cuspicaudus). Materiales y métodos. Al inicio de la alimentación exógena de Sorubim cuspicaudus, se ofreció zooplancton producido en mesocosmos (T1), zooplancton silvestre (T2) y nauplios de Artemia (T3), en concentración de 10.000 zoop/L, dos veces al día, durante seis días. Se utilizaron 18 acuarios de cinco litros de volumen útil, con densidad de 25 Larvas/L, seis réplicas por tratamiento en un diseño al azar. Se estimaron la ganancia en peso (Gp) y longitud (Gl), tasa de crecimiento específico (G), sobrevivencia (S), resistencia al estrés (Re), mortalidad acumulada (Ma) y mortalidad por canibalismo (Mc). Resultados. Las larvas alimentadas con mesocosmos presentaron la mayor sobrevivencia (81.3±15.9%); aunque el mejor crecimiento lo presentaron las larvas alimentadas con zooplancton silvestre (T2) las cuales presentaron la mayor mortalidad (42.0±10.7%) y la menor resistencia al estrés (30.0±33.0%). El canibalismo se observó en todos los tratamientos, oscilando entre 4.0 (T2) y 14.3% (T1) sin diferencias significativas entre estos valores (p>0.05). Conclusiones. El uso de zooplancton producido bajo condiciones controladas permitió una alta sobrevivencia, adecuado desempeño y resistencia de las larvas, perfilándose como alternativa viable en la primera alimentación de bagre blanco.
Objective. Assess the effect of different live prey in the larviculture of Trans-andean shovelnose catfish (Sorubim cuspicaudus). Materials and methods. At the beginning of exogenous feeding, zooplankton produced in mesocosm (T1), wild zooplankton (T2) and brine shrimp (T3), in concentrations of 10.000 zoop/L, were fed twice daily, for six days. 18 five-liter useful volume aquariums were used, with density of 25 Larvas/L, and six replicas per treatment in a random design. The increase in weight (Gp) length (Gl), the specific growth rate (G), survival (S), stress resistance (Re), accumulated mortality (Ma) and mortality due to cannibalism (Mc) were measured. Results. Larvae fed with mesocosm presented the highest survival rate (81.3±15.9%), although larvae fed wild zooplankton (T2) had the highest growth (Gp, Gl, G), and recorded the highest accumulated mortality (42.0±10.7%) and the lowest resistance to stress (30.0±33.0%). Cannibalism was observed in all treatments, ranging from 4.0 (T2) to 14.3% (T1) no significant difference between these values (p>0.05) was observed. Conclusions. The use of zooplankton produced under controlled conditions allows high survival, adequate performance and resistance of the larvae, emerging as viable alternative for the first feeding of white catfish.
Sujets)
Animaux , Artemia , Aliments , LarveRésumé
This study set out to evaluate, via a mesocosm experiment, the influence of the temperature and concentration of nutrients (N and P) in the abundance of periphytic algae (except Bacillariophyceae) of the upper Paraná river floodplain. The experiment was designed using 5 treatments: a control (C), added nutrients (P+, N+, NP+) at 25C, and without added nutrients at 15C. Glass slides were used for periphytic algae colonization, and the samples were taken on the 15th and 31st days following colonization. Canonical Correspondence Analysis revealed a clear separation among treatment groups due to temperature and added nutrients. A decrease in temperature affected the abundance of periphytic algae classes, especially in the reduction of the relative density of Cyanophyceae and increase in Zygnemaphyceae. The artificial addition of nutrients especially P altered the structure of the periphytic algae communities. The relative densities of the classes, in general, increased with the addition of nutrients. Phosphorus may be considered a driver of periphytic algae, as can be seen by the rapid response after artificial enrichment.
O estudo visou avaliar, em um experimento de mesocosmos, a influência da temperatura e de concentrações de nutrientes na abundância das algas perifíticas (exceto Bacillariophyceae) na planície de inundação do alto rio Paraná. O delineamento experimental constituiu-se de cinco tratamentos: controle (C) e adição de nutrientes (P+, N+ e NP+) a 25C, e frio (F) com diminuição da temperatura a 15C e sem adição de nutrientes. Lâminas de vidro foram utilizadas para colonização das algas perifíticas, e as amostragens foram feitas entre o 15 e o 31 dia de sucessão. Pela Análise de Correspondência Canônica, pode-se observar uma clara separação entre os tratamentos devido à temperatura e adição de nutrientes. A diminuição de temperatura afetou a abundância das classes de algas perifíticas, principalmente pela redução da densidade relativa de Cyanophyceae e aumento de Zygnemaphyceae. O enriquecimento artificial de nutrientes, principalmente P, alterou a estrutura da comunidade de algas perifíticas, em termos de densidade das classes algais. As densidades relativas das classes, em geral, aumentaram com a adição de nutrientes. O fósforo pode ser considerado direcionador na densidade das algas perifíticas, como pode ser observado pela rápida resposta após os enriquecimentos artificiais.