Food composition and selectivity of Mysis relicta (Loven) in Lake Breiter Luzin

摘要

Mysis relicta (Crustacea: Mysidacea) is widely distributed in brackish and freshwater in previously glaciated environments in the northern hemisphere. Mysids perform diurnal vertical migrations, remaining near the bottom during daytime and ascend into upper water layers at night (Beeton Bowers 1982). Being omnivorous, they feed on small particles such as phytoplankton or detritus by filter feeding (Linden Kuosa 2004, Grossnickle 1979), and can switch to a predatory feeding mode to actively capture prey organism like zooplankton (Grossnickle 1982). Consuming both benthic and pelagic food, mysids are an important link between these habitats. Because mysids also are a major food resource for planktivorous fish (Morgan et al. 1978), they are of great ecological importance in the food web. Mysids can use a wide variety of food sources depending on availability. Thus diet composition and selectivity of mysids may differ among lakes depending on the prey community. In Germany, M. relicta occurs in four lakes, three of which are situated in the Feldberg Lake District (Scharf Koschel 2004). Information on the diet of mysids in this region are only available from a single sampling occasion (Wa-terstraat 1988). In the current study, the diet of M. relicta in Lake Breiter Luzin, the largest lake in this district, was examined. Attention was focused on food composition and selectivity in different seasons.