Feeding ecology of vimba (Vimba vimba L., 1758) in terms of size groups and seasons in Lake Sapanca, Northwestern Anatolia

Abstract

The seasonal changes of diet in the guts of 298 vimbas (Vimba vimba L.) caught on a monthly basis in Lake Sapanca from August 2003 to July 2004 were analyzed. V. v i m b a fed on ostracods, gastropods, Dreissena polymorpha (mollusks), fish larvae, macrophytes, oligochaetes, chironomids, phytoplankton, and detritus. Te gut fullness index (GFI) indicated that vimbas increased their feeding activity in summer and decreased it in winter. Te correlation between GFI and temperature was significant (0.839, P < 0.01). Te water temperature shif was one of the critical environmental factors affecting the feeding of vimbas in Lake Sapanca. Te lowest similarity of diet composition was between the juvenile vimbas in autumn and the adult vimbas in spring (cluster analysis), while the highest similarity of diet composition was between adult individuals in autumn and winter (cluster analysis). In both size groups and in all seasons, the main food items were macrophytes, D. polymorpha, and phytoplankton (particularly bacillariophytes). Of animal food items, adult individuals fed mostly on D. polymorpha, while ostracods were consumed only by juvenile fish in spring, summer, and autumn. Te benthic-omnivorous strategy of vimba is demonstrated by the high abundance of plant foods in their guts, confrming this mixed type of diet. © TÜBİTAK.