Diet and trophic structure of the fish fauna in a subtropical ecosystem: impoundment effects

Abstract

This study examined the diet and trophic structure of the fish fauna, over temporal and spatial scales, as affected by the impoundment of the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Sampling was conducted before (March 1997 - February 1998) and after the impoundment (March 1999 - February 2000), at four sampling sites. The stomach contents were analyzed by the volumetric method. The species could be organized in 10 trophic guilds: algivores, carcinophages, detritivores, herbivores, aquatic insectivores, terrestrial insectivores, invertivores, omnivores, piscivores, and planktivores; the first and last guilds were represented only in the post-impoundment period. Similarity patterns and feeding changes were summarized by a non-metric Multi-dimensional Scaling (nMDS) analysis and statistically tested by a Permutational multivariate analysis of variance (PERMANOVA). Most species showed feeding changes, except for the piscivores and detritivores. These changes were related to the temporal factor (impoundment phases), such as reduced intake of benthic organisms and allochthonous food, which were usually replaced by resources from the reservoir itself (algae, microcrustaceans, and fish), simplifying the food spectrum of the fish fauna. A different indicator of food resources (IndVal) corroborated these changes in the feeding of the species. The proportions of the trophic guilds evaluated based on the catch per unit of effort (CPUE) and tested by ANOSIM were significantly different before and after the impoundment. Herbivores and piscivores were the guilds that contributed (SIMPER) to these differences, especially the high increase in biomass of the piscivore guild after the impoundment. Variations in the abundance of trophic guilds were more directly related to changes in the feeding habits of the fish fauna than to increases in the number and biomass of the species that constitute these guilds.

Influence of limnological zones on the spatial distribution of fish assemblages in three Brazilian reservoirs

“…In São Simão Reservoir, however, the lacustrine zone supported more individuals than the riverine zone. One of the explanations for this is the high abundance of piscivorous species in this reservoir, which also was observed by Delariva et al (2013) at Salto Caxias Reservoir. Visual predators are well adapted to lacustrine habitats with high transparency (Guthrie and Muntz, 1993).…”

Does the oscillation of the water volume of the reservoir influence in the same way in fish diet?

“…The strategy of using the most available resources is essential because allows the species to persist in the environments, once it allows them to broaden their resource range (Delariva et al, 2013) allowing tolerate the most severe impacts.…”

Variação temporal e espacial na dieta de Trachelyopterus galeatus (Siluriformes, Auchenipteridae) em dois reservatórios no semiárido Neotropical

“…Seguindo a teoria do forrageamento ótimo (MacArthur & Pianka, 1966), em que os organismos são adaptados para obter alimento com o maior valor energético gastando o mínimo possível de energia, observou-se que a espécie também consumiu peixes, insetos, além de vegetais, detrito/sedimento e material orgânico. A maioria das espécies de peixes de água doce apresenta mudanças sazonais em suas dietas, decorrente das diversas táticas alimentares associadas à captura de itens, que contribui para o maior sucesso na predação e exploração dos recursos alimentares disponíveis no ambiente (Abelha et al, 2001;Delariva et al, 2013). Essa estratégia é essencial, pois possibilita que as espécies possam persistir nos ambientes, uma vez que permitem alargar sua gama de recursos (Delariva et al, 2013).…”

“…A maioria das espécies de peixes de água doce apresenta mudanças sazonais em suas dietas, decorrente das diversas táticas alimentares associadas à captura de itens, que contribui para o maior sucesso na predação e exploração dos recursos alimentares disponíveis no ambiente (Abelha et al, 2001;Delariva et al, 2013). Essa estratégia é essencial, pois possibilita que as espécies possam persistir nos ambientes, uma vez que permitem alargar sua gama de recursos (Delariva et al, 2013). Para um peixe se especializar em determinado recurso, duas regras devem satisfazer esta condição: o peixe deve apresentar estrutura morfológica hábil para exploração do alimento e o recurso deve estar em quantidade suficiente, em biomassa, para suprir as necessidades do predador (Lagler et al, 1977).…”