ABSTRACT
Hg accumulation in fish is influenced by several factors including seasonality. In the Amazon, ecosystems are marked by strong seasonal variation in precipitation, which leads to drastic changes in the water level of lakes and rivers. The aim of this study was to evaluate Hg levels in muscle of detritivorous, herbivorous and omnivorous fish from an Amazon lake (Madeira River Basin, Amazonas, Brazil) over four seasons (rising water, high water, falling water and low water). We hypothesized that total Hg concentration varies during the seasons. The results indicate that total Hg levels in detritivorous fish were higher in rising and low water seasons while in herbivorous and omnivorous fish the total Hg concentration was higher during the rising water season. The hypothesis was supported by the results. Additionally, the study provides evidence that Hg levels in fish with different feeding habits are influenced by the flood pulse of the Amazon region.
Subject(s)
Diet , Environmental Exposure/analysis , Fishes/metabolism , Floods , Lakes , Mercury/metabolism , Water Pollutants, Chemical/metabolism , Animals , Brazil , Environmental MonitoringABSTRACT
The total supply of fish available for human consumption will depend more of the expansion of low trophy level fish farming than of wild-caught fish. Aquatic plants used at treatment of aquaculture wastewater have been showed like an alternative to exclusive diet feed. The aquatic fern, Azolla filiculoides is an example with high level of protein. Consequently, more research on feed requirements of herbivorous fish is required. The aim of this study was to evaluate the growth performance and feed efficiency of juvenile grass carp (Ctenopharyngodon idella) fed with three different diets using low lipid feed and water fern (Azolla filiculoides). The experiment was carried out in nine (9) tanks of 300 L capacity with three fish per tank (initial body weight = 55,43g). Feeding rate was 2.5% Fish were fed on two times a day with three treatments (R= Diet/Azolla on dry weight) R= 2.5; R = 5 and R= 10. The specific growth rate (SGR = 1.39%), daily growth gain (DGG = 1.06 g / day) and were significantly (p 0.05) affected by treatment and were highest at R= 5.
A oferta de pescado para o consumo humano dependerá mais da expansão do cultivo de peixes que se alimentam dos primeiros níveis tróficos do que daqueles oriundos da pesca extrativa. Plantas aquáticas usadas em fitotratamento de efluentes de aquacultura vêm sendo referidas como uma alternativa alimentar ao uso exclusivo de rações. A Azolla filiculoides é uma pteridófita que apresenta alto nível protéico. Assim, pesquisas sobre as exigências nutricionais de espécies herbívoras são necessárias. O objetivo principal deste estudo foi avaliar o crescimento e eficiência alimentar de juvenis de carpa capim (Ctenopharyngodon idella) alimentadas com três relações (R) entre ração com baixo teor lipídico e a planta aquática in natura (Azolla filiculoides). O experimento foi conduzido em nove reservatórios com capacidade de 300L e três indivíduos por unidade (Peso Inicial = 53,43g). A taxa alimentar diária foi de 2,5%, dividida em duas refeições, constituindo três tratamentos com diferentes relações entre a ração e a Azolla filiculoides na matéria seca (R=Ração/Azolla), R=2,5, R=5 e R=10. A taxa de crescimento específico (TCE = 1,39%) e o ganho peso diário (GPD = 1,06 g/dia) foram melhores na relação Ração / Azolla R = 5.
ABSTRACT
The total supply of fish available for human consumption will depend more of the expansion of low trophy level fish farming than of wild-caught fish. Aquatic plants used at treatment of aquaculture wastewater have been showed like an alternative to exclusive diet feed. The aquatic fern, Azolla filiculoides is an example with high level of protein. Consequently, more research on feed requirements of herbivorous fish is required. The aim of this study was to evaluate the growth performance and feed efficiency of juvenile grass carp (Ctenopharyngodon idella) fed with three different diets using low lipid feed and water fern (Azolla filiculoides). The experiment was carried out in nine (9) tanks of 300 L capacity with three fish per tank (initial body weight = 55,43g). Feeding rate was 2.5% Fish were fed on two times a day with three treatments (R= Diet/Azolla on dry weight) R= 2.5; R = 5 and R= 10. The specific growth rate (SGR = 1.39%), daily growth gain (DGG = 1.06 g / day) and were significantly (p 0.05) affected by treatment and were highest at R= 5.
A oferta de pescado para o consumo humano dependerá mais da expansão do cultivo de peixes que se alimentam dos primeiros níveis tróficos do que daqueles oriundos da pesca extrativa. Plantas aquáticas usadas em fitotratamento de efluentes de aquacultura vêm sendo referidas como uma alternativa alimentar ao uso exclusivo de rações. A Azolla filiculoides é uma pteridófita que apresenta alto nível protéico. Assim, pesquisas sobre as exigências nutricionais de espécies herbívoras são necessárias. O objetivo principal deste estudo foi avaliar o crescimento e eficiência alimentar de juvenis de carpa capim (Ctenopharyngodon idella) alimentadas com três relações (R) entre ração com baixo teor lipídico e a planta aquática in natura (Azolla filiculoides). O experimento foi conduzido em nove reservatórios com capacidade de 300L e três indivíduos por unidade (Peso Inicial = 53,43g). A taxa alimentar diária foi de 2,5%, dividida em duas refeições, constituindo três tratamentos com diferentes relações entre a ração e a Azolla filiculoides na matéria seca (R=Ração/Azolla), R=2,5, R=5 e R=10. A taxa de crescimento específico (TCE = 1,39%) e o ganho peso diário (GPD = 1,06 g/dia) foram melhores na relação Ração / Azolla R = 5.