Seasonal variation in the diet of the sardine Triportheus guentheri (Garman, 1890) (ACTINOPTERYGII: CHARACIDAE), in the Sobradinho Reservoir, São Francisco River, BA

Abstract

This study aims to evaluate the use of food resources by T. guentheri and verify possible seasonal variations in diet in response to water level oscillation of Sobradinho reservoir. Bimonthly night samplings were conducted between November 2007 and September 2009, in the lotic, transitional and lentic stretches of the reservoir, using gillnets (12, 15, 20, 25, 30 and 35 mm between adjacent nodes). The stomach content analysis was based on the frequency of occurrence and gravimetric methods. A total of 1,029 specimens, with standard length (SL) ranging between 37 and 150 mm were analyzed. The diet was mainly composed of aquatic insects, especially Ephemeroptera item (subimages), which predominated in both periods. Trophic niche amplitude values were low, regardless of the sampling period (Ba = 0.18 during flooding, and Ba = 0.03 in the dry season). The diet composition showed no correlation with the seasonal variation of the reservoir water level.