Dietary patterns of five freshwater fish species in a large Mediterranean lake

The diet of five freshwater fish species of Lake Trichonis, the largest natural lake of Greece, was studied. Specifically, the studied species were Atherina boyeri, Luciobarbus albanicus, Leucos panosi, Scardinius acarnanicus and Tropidophoxinellus hellenicus. The diet analysis was based on stomach content analysis of seasonal samples collected during 2019 by experimental Nordic multimesh gillnets. Additionally, trophic indices were estimated (Shannon-Wiener, Levins', Schoener, Trophic level) so as to investigate each species' feeding diversity, trophic niche breadth, trophic level as well as their trophic competition and overlap. Moreover, the annual and the seasonal relative condition factor was estimated. The diet analysis indicated a tendency of the studied species to omnivorous feeding strategy and a seasonal fluctuation in their diet composition. In addition, the estimated trophic indices revealed similar feeding behavior and significant diet overlap between species, suggesting narrow partitioning of the food resources. However, the relative condition factor ranged between 0.973 and 1.041, indicating a state of wellbeing for the fish species and possibly sufficient food availability.