INFLUENCE OF CAGE FISH FARMING ON THE DIET AND BIOLOGICAL ATTRIBUTES OF Galeocharax knerii IN THE CHAVANTES RESERVOIR, BRAZIL
The aim of the present study was to evaluate the diet and biological attributes of the population of Galeocharax knerii residing near net cage fish farming activities in the Chavantes reservoir (Paranapanema River, Brazil) to check their possible impacts. Samples were collected from two populations:...
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Veröffentlicht in: | Boletim do Instituto de Pesca 2013-01, Vol.39 (2), p.157-167 |
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Zusammenfassung: | The aim of the present study was to evaluate the diet and biological attributes of the population of Galeocharax knerii residing near net cage fish farming activities in the Chavantes reservoir (Paranapanema River, Brazil) to check their possible impacts. Samples were collected from two populations: one near the net cages (NC) and one from an area not influenced by these cages denominated the "reference site" (RS). Monthly sampling was carried out from March 2008 to February 2009. Fish were caught with a standardized effort using gill nets deployed for 14 hours. The alimentary index (AI) and degree of repletion (RD) were calculated to determine diet composition. Analyses of the sex ratio and the gonadosomatic index (GSI) were also performed. The calculations of AI revealed that fish wastes constituted the most frequent food item in the diet in both study areas (NC = 70.43; RS = 87.55), followed by the consumption of Apareiodon affinis (AI = 29.56), which was abundant near the NC, and prawn at the reference site (AI = 12.28). The sex ratio differed from 1:1 and mature individuals were only found in the population near the NC. The findings demonstrate that G. knerii indirectly benefits from the input of organic matter, using small fish as its main food resource. We conclude that the activities of fish farming influence diet and biological attributes of the species G. knerii, evidenced mainly by higher feeding activity, numerical abundance and biomass in the area of the cages.Original Abstract: O objetivo deste estudo foi avaliar a dieta e atributos biologicos das populacoes de Galeocharax knerii residentes ao redor de uma piscicultura em tanques-rede no reservatorio de Chavantes, para verificar seus possiveis impactos. Para isto, foram coletadas amostras da populacao em torno dos tanques-rede (TR) e, em uma area sem influencia da piscicultura, denominado "controle" (CT). As amostragens ocorreram mensalmente, de marco 2008 a fevereiro de 2009. Os peixes foram capturados com rede de espera com esforco padronizado, expostas por 14 horas. Para determinar a composicao da dieta, foi calculado o indice alimentar (IAi) e o grau de replecao (GR). Foi analisada a razao sexual e indice gonodossomatico (IG). O calculo do indice alimentar (IAi) revelou que restos de peixes constituiu o item mais frequente na dieta em ambas as areas de estudo (TR = 70,43; CT = 87,55) seguido pelo consumo da especie de peixe Apareiodon affinis (IA = 29,56), abundante em torno dos tanques, |
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ISSN: | 0046-9939 |