Feeding habits of the Macedonian shad, Alosa macedonica (Vinciguerra, 1921) in Lake Volvi (Greece): Seasonal and ontogenetic changes

Feeding habits of the Macedonian shad (Alosa macedonica), an endemic species in Lake Volvi (Macedonia, Greece), were studied during the period October 1995-September 1996. At the beginning of summer and throughout autumn, feeding was more intense, decreasing during winter as well as in May and August. Feeding intensity was found to be directly dependent on water temperature. A. macedonica fed mainly on copepods (47.7% in terms of number), but according to Pearre's electivity index, cladocerans (18.5% in terms of number) were the most preferred prey. Although rotifers represented the third trophic group (17.1% in terms of number), they seem to be avoided. The diet composition changed with season and fish size. During summer-autumn, the diversity of food increased Older fish (170-219 mm) were characterized by a consumption of larger prey, such as fish. Negative and positive selection was present for the smaller (100-200 ìm) and the larger (200-300 ìm) size class of Bosmina longirostris, respectively, only during the period of population explosion of this species.