Abstract
AIM: The aim of this study was to identify the cladocerans species from the gut contents of fishes sampled in an oxbow lake from Taquari River Basin, MS, with the specific view of investigating the importance of these crustaceans in the fishes diets; METHODS: Sampling was carried out in April and August of 2005 (dry season) and January of 2006 (wet season). The fish were captured with a sieve. In the laboratory, individuals were identified and stomachs were removed and weighed. The stomach contents were identified, and a Feeding Index calculated; RESULTS: The items most consumed by fishes were filamentous algae, Cladocera and detritus. The Cladocera were especially important in the August and January samples, and consisted primarily of Chydoridae; cladocerans were most consumed by species of Serrapinnus and by Mesonauta festivus. Fish fed more in April, with decreases occurring in stomach fullness on the other two sampling dates. CONCLUSIONS: Cladocerans associated with macrophytes may be an important food source for small fish individuals in marginal lakes from Taquari River Basin. The relative importance of the Chydoridae in the guts may have been due to the high relative abundance and species richness of this group in the environment. A short discussion on fish feeding habits was included in the text.
Highlights
Marginal lakes of floodplain rivers are shallow environments, generally with extensive macrophyte communities that provide a great variety of habitats, representing a rich source of food and protection from predators for the associated invertebrates and fish (Fernando, 1994; Agostinho et al, 2003).Cladocerans are important components of the invertebrate communities of aquatic macrophytes, presenting elevated richness and abundance (Wisniewski et al, 2000; Güntzel et al, 2010), being an important source of food for various vertebrates and invertebrates (De Bernardi et al, 1987).According Elmoor-Loureiro and Soares (2010), this group of microcrustaceans was found in the gut content of several Brazilian fishes
The objective of the present study was to analyze the trophic relationships between small fish individuals and cladocerans associated with macrophytes of a marginal floodplain lake, with the aim of determining the importance of this group of microcrustaceans in the fish diets
The greatest degrees of fullness occurred in April, as indicated by the Repletion Index values (April: 0.0241; August: 0.0087 and January: 0.0099)
Summary
Marginal lakes of floodplain rivers are shallow environments, generally with extensive macrophyte communities that provide a great variety of habitats, representing a rich source of food and protection from predators for the associated invertebrates and fish (Fernando, 1994; Agostinho et al, 2003).Cladocerans are important components of the invertebrate communities of aquatic macrophytes, presenting elevated richness and abundance (Wisniewski et al, 2000; Güntzel et al, 2010), being an important source of food for various vertebrates and invertebrates (De Bernardi et al, 1987).According Elmoor-Loureiro and Soares (2010), this group of microcrustaceans was found in the gut content of several Brazilian fishes. Marginal lakes of floodplain rivers are shallow environments, generally with extensive macrophyte communities that provide a great variety of habitats, representing a rich source of food and protection from predators for the associated invertebrates and fish (Fernando, 1994; Agostinho et al, 2003). Cladocerans are important components of the invertebrate communities of aquatic macrophytes, presenting elevated richness and abundance (Wisniewski et al, 2000; Güntzel et al, 2010), being an important source of food for various vertebrates and invertebrates (De Bernardi et al, 1987). According Elmoor-Loureiro and Soares (2010), this group of microcrustaceans was found in the gut content of several Brazilian fishes. The objective of the present study was to analyze the trophic relationships between small fish individuals and cladocerans associated with macrophytes of a marginal floodplain lake, with the aim of determining the importance of this group of microcrustaceans in the fish diets The preference of fish for Cladocera has been attributed to their body form and size, conspicuous swimming motion, and less efficient escape response, as compared to the Copepoda (Maia-Barbosa and Matsumura-Tundisi, 1984). Twombly and Lewis Junior (1989) provided evidence that cladocerans (at least the planktonic taxa) in floodplain lakes can suffer high degrees of fish predation.
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