Abstract
This study aimed to identify shifts in the Serrasalmus brandtii Lütken, 1875 diet related to body size. Specimens were collected from April 1992 to January 1993 at the Cajuru Reservoir, in the Pará River, São Francisco River Basin, by seining the shore with nets of nylon, 1 mm opening, and with gill nets. Stomach contents of 152 individuals measuring 15-192 mm SL were examined. Food items were identified and weighed separately. For qualitative analysis, the frequency of occurrence method was used. The relative importance of each food component was determined based on the alimentary index (IAi). The frequencies of occurrence data were subjected to cluster analysis using the Canberra coefficient of dissimilarity and UPGMA as the cluster method. Distinctive gradual changes in food habits, associated with body size, were identified in this species. The smaller individuals fed predominantly on microcrustaceans and insect larvae. The intermediate size classes ingested insects, fish fins, fish scales, and chunks of fish flesh, in this order of importance. For the larger pirambebas, fish was the most abundant food category identified, followed by insects.
Highlights
Piranhas and pirambebas are widely spread fishes in South America that proliferate in lentic environments (Barbosa, 1980)
The purpose of this work was to evaluate the ecological role played by individuals of different sizes of the pirambeba Serrasalmus brandtii Lütken, 1875 in the Cajuru Reservoir through the analysis of their stomach contents
Study area The Cajuru Hydroelectric Power Plant reservoir belongs to the Companhia Energética de Minas Gerais (CEMIG) (Fig. 1) and is located at Carmo do Cajuru, in Divinópolis and Cláudio counties
Summary
Piranhas and pirambebas are widely spread fishes in South America that proliferate in lentic environments (Barbosa, 1980). They have piscivorous habits (Nico & Taphorn, 1988; Braga, 1975; Northcote et al, 1986; Bistoni & Haro, 1995) and are known to be mutilating predators, feeding on fish fins, scales, and other body parts of their prey (Goulding, 1980; Leão et al, 1991; Machado-Allison & Garcia, 1986; Nico & Taphorn, 1988; Northcote et al, 1987). The body growth of these fish is followed by morphological changes (MachadoAllison & Garcia, 1986) that influence their food habits (Winemiller, 1989), accounting for the different trophic levels occupied by them during their life history.
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