Abstract
This study described the variations seasonal and ontogenetic of Salminus hilarii diet. Samples were collected in the Sorocaba River, São Paulo, Brazil, one of the few rivers where individuals of the species still occur in a higher frequency. The preys consumed were analyzed by Importance Alimentary Index (AIi). To determine similarities between year seasons, the AIi data were analyzed by the Morisita-Horn index and reduced in cluster analysis, along with a statistical comparison made by one-way ANOSIM test (5%). The feeding activity was analyzed according to the stomach repletion index and compared among the year seasons using non parametric variance analysis Kruskal-Wallis test (5%). Comparison of prey consumed between immature and adult individuals was made by Spearman correlation (5%). A Pearson correlation (5%) was applied between the standard length of the fish and prey consumed, as well as between the mouth and prey heights. The analyzes of stomach contents showed that the diet of this species was exclusively piscivorous, with significant difference of prey consumption during the period, the same happening among adult and immature individuals. It was observed that these fishes use to swallow their prey whole and that significant correlations between size of predator and prey size can be observed. There is also correlation between the mouth height and the maximum prey depth. Salminus hilarii feeds on the available prey, and the species food composition and feeding activity depends on prey`s abundance, their size and morphology, as do the water temperatures.
Highlights
IntroductionThe diet analysis is important for studies about predation, competition and food chains, as it permits the access to the knowledge about fish feeding ecology (Costello, 1990)
The diet analysis is important for studies about predation, competition and food chains, as it permits the access to the knowledge about fish feeding ecology (Costello, 1990).Fish feeding behavior is the consequence of evolutionary sequences, which result in the establishment of the alimentary spectrum presented by each species, in the order to select, Braz
The Sorocaba River basin is located in the São Paulo state, Brazil, which is part of the high Parana river basin
Summary
The diet analysis is important for studies about predation, competition and food chains, as it permits the access to the knowledge about fish feeding ecology (Costello, 1990). Fish feeding behavior is the consequence of evolutionary sequences, which result in the establishment of the alimentary spectrum presented by each species, in the order to select, Braz. Variations of Salminus hilarii diet capture and digest a particular food type, and helps one to understand to figure out aspects related to the roles the several species play within the environment. Though a feeding specificity may be commonly described for fish studies, such diets may vary considerably according to the sites, year season and food availability. Seasons may influence feeding rhythms as temperatures vary and even when some activities occur during the day or night, as food resources may occur at distinct compositions (Zavala-Camin, 1996)
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