11 research outputs found
Composição e abundância de peixes da interface entre as águas abertas e bancos de macrĂłfitas e sua dinâmica nos perĂodos de crepĂşsculos matutino e vespertino, no lago CatalĂŁo, Amazonas, Brasil (Composition and abundance of fishes in the interface between open water and macrophyte banks, and the dynamics of this interface during morning and evening twilight, in lake Catalao, Amazonas, Brazil)
This work studied the composition and abundance of the fishes that move between macrophyte
banks and open water during the morning twilight (CM) and afternoon twilight (CV). The collections
were made using gillnets, along banks of Paspalum repens, at CatalĂŁo lake, in Amazonas, Brazil. A
total of 222 individuals and 37 species were collected. Of these, 130 individuals were collected
during the CM and 92 during the CV; 80 individuals were leaving during the CM and 40 individuals
were leaving during the CV. Auchenipterus nuchalis, Pellona castelnaeana, Triportheus angulatus and
T. albus were the most common and concentrated species collected in the CM and Pimelodus blochii
was the most common species collected in the CV
Contribution of anadromous fish to the diet of European catfish in a large river system
Many anadromous fish species, when migrating from the sea to spawn in fresh waters, can potentially be a valuable prey for larger predatory fish, thereby efficiently linking these two ecosystems. Here, we assess the contribution of anadromous fish to the diet of European catfish (Silurus glanis) in a large river system (Garonne, southwestern France) using stable isotope analysis and allis shad (Alosa alosa) as an example of anadromous fish. Allis shad caught in the Garonne had a very distinct marine delta(13)C value, over 8 per thousand higher after lipid extraction compared to the mean delta(13)C value of all other potential freshwater prey fish. The delta(13)C values of European catfish varied considerably between these two extremes and some individuals were clearly specializing on freshwater prey, whereas others specialized on anadromous fish. The mean contribution of anadromous fish to the entire European catfish population was estimated to be between 53% and 65%, depending on the fractionation factor used for delta(13)C
Trace Elements and Carbon and Nitrogen Stable Isotopes in Organisms from a Tropical Coastal Lagoon
Trace elements (Fe, Mn, Al, Zn, Cr, Cu, Ni, Pb, Cd, Hg, and As) and stable isotope ratios (δ13C and δ15N) were analyzed in sediments, invertebrates, and fishes from a tropical coastal lagoon influenced by iron ore mining and processing activities to assess the differences in trace element accumulation patterns among species and to investigate relations with trophic levels of the organisms involved. Overall significant negative relations between trophic level (given by 15N) and trace element concentrations in gastropods and crustaceans showed differences in internal controls of trace element accumulation among the species of different trophic positions, leading to trace element dilution. Generally, no significant relation between δ15N and trace element concentrations was observed among fish species, probably due to omnivory in a number of species as well as fast growth. Trace element accumulation was observed in the fish tissues, with higher levels of most trace elements found in liver compared with muscle and gill. Levels of Fe, Mn, Al, and Hg in invertebrates, and Fe and Cu in fish livers, were comparable with levels in organisms and tissues from other contaminated areas. Trace element levels in fish muscle were below the international safety baseline standards for human consumption