Abstract
AIM: The aim of the present study was to evaluate the diet and biological attributes of the population of Apareiodon affinis residing near net-cage fish farming activities in the Chavantes reservoir. METHODS: 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 Mar/2008 to Feb/2009. Fish were caught with a standardized effort using gill nets deployed for 14 hours. After all individuals were measured (standard length) and weighed (total weight, carcass weight , body weight without gonads). To determine the composition of the diet, the alimentary index was calculated (AI). We also calculated the length-weight relationship, condition factor, gonad-somatic index (GSI ) and reproductive potential. RESULTS: A total of 3050 individuals were caught. The results of the (AI) revealed that the item detritus was the main food used for populations of A. affinis studied in two areas (NC = 73.1% and RS = 95.7%). The use of feed on diet A. affinis was recorded for the populations of NC adding (20.5%) of the total items consumed by the population. The resident populations residing near net-cage showed higher condition factor and more reproductive period. CONCLUSIONS: The results show the ability of the species to benefit from the input of organic matter from fish farming activities, inserting a new item in their diet (ration). This work indicates that the species A. affinis managed to establish near net-cage, allocating enough energy to increase their reproductive period and maintain viable populations close to net-cage, evidenced by the high abundance. This study suggests that systems of fish farming in net-cage influence diet and biological attributes of the species A. affinis residents Chavantes reservoir, Brazil.
Highlights
In recent decades, Brazilian hydrographic basins have been dammed in order to generate hydroelectricity, according to government guidelines, to meet the growing energy demanding
This study aimed to evaluate the influence of fish farming in Chavantes reservoir, Paranapanema River on the diet and biological attributes of the fish species Apareiodon affinis captured around a system of fish farm cages, compared to a reference site
The length-weight relationship was examined in two manners; firstly, we considered the total wet weight of the fish and, secondly, we considered the wet weight of carcasses
Summary
Brazilian hydrographic basins have been dammed in order to generate hydroelectricity, according to government guidelines, to meet the growing energy demanding. Encouraged by the government, cage-farming activities are currently expanding in reservoirs of hydroelectric plants, where the inclusion of these systems may be a new source of impact on the ichthyofauna of reservoirs (HenrySilva and Cardoso 2008; Lachi and Sipaúba-Tavares, 2008; Brasil, 2009, 2011). According to the Agência Paulista de Tecnologia dos Agronegócios (APTA, 2008), there are 360fish farmers in the middle Paranapanema River region, and at least 40 species of freshwater fish in Brazil are used in aquaculture, which represents only 1.5% of all known species (Godinho, 2007). Fish farming activities have been increasing and becoming an important source of protein for human consumption. Brazil has a great potential for the development of aquaculture, due to its vast territory and favorable climate conditions, which is internationally acknowledged (Pavanelli et al, 2008)
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