Ecomorfologia trófica de peixes bioindicadores de riachos submetidos a diferentes graus de antropização

Abstract

Aquatic ecosystems have suffered recurrent environmental impacts that imply changes in biota, with repercussions for their conservation. In this context, the present study evaluates the variations in ecomorphological and trophic structures of assemblages of bioindicator fishes of streams under different degrees of anthropization (urban: Cambé, periurban: Cafezal, and rural: Taquara), in the Tibagi River basin (Paraná, Brazil). The diets of 20 species of fish recognized as bioindicators of the sampled streams were analyzed, using the criterion of the individual indicator value (IndVal). For each individual, 26 ecomorphological indices were calculated. Multivariate analysis of variance was applied to test whether there are significant differences among the scores of the principal component analysis performed with ecomorphological indices of the individuals, investigating whether the streams present different ecomorphological structures. Variations and similarities in diet were verified applying the detrended correspondence analysis. The canonical redundancy analysis was applied to assess the relationships between ecomorphology (ecomorphological indexes) and trophic ecology (food diets) of the bioindicator species. The null hypothesis that the ecomorphological and trophic diversifications of the assemblages of bioindicator fish in the different categories of streams studied does not depend on historical (phylogenetic) relationships between species was tested by the partial Mantel and Mantel tests. An analysis of the diets revealed the occurrence of 11 categories of food resources, for which were calculated the relative importance indexes (IIR): seaweed, insect cocoon, detritus, immature insect, adult insect, rare resources, unidentified resources, microcrustacean, mollusk, fish and vegetable. The formation of three distinct ecomorphotypes (urban, peri-urban, and rural) was verified corresponding to different degrees of anthropization of the hydrographic basins. In relation to the trophic pattern, adult insect, immature insect, detritus, and plant source presented highest values of IIR. The rural stream had the greatest diversity of food resources, in contrast to the urban and periurban. There is evidence that a more urbanized stream presents less ecomorphological diversification of fish assemblage and diversity of resources available to be potentially exploited by these species, regardless of phylogenetic relationships among species. Therefore, the body shape of the bioindicator species of the urban, periurban and rural streams has proven to be a good predictor of the feeding of these species. Trophic ecomorphology has proven to be an important tool for diagnosing responses to anthropogenic changes that commonly affect aquatic ecosystems of lesser order.