CanGammarus aequicauda(Amphipoda) suppress a population ofBaeotendipes noctivagus(Chironomidae) in a hypersaline lake? A case of Lake Moynaki (Crimea)

Abstract

The ecosystems of hypersaline waters are characterized by the simplified trophic webs with the ‘loss’ of predators. In the absence of predators, their role can be effectively performed by omnivorous as Gammaridae species. In Lake Moynaki, a small hypersaline lake, Gammarus aequicauda is one of the most abundant animal species along with chironomid larvae Baeotendipes noctivagus. Both these species are promising objects to use in polyaquaculture, and this adds an importance to know their trophic relations. To analyse G. aequicauda feeding on B. noctivagus, the field and experimental studies were conducted in 2018 and 2019. In two habitats (Ruppia thickets and free water), the abundance of both species significantly differed, and in the thickets of Ruppia, the Gammarus abundance was higher, and of chironomid larvae was less. Taking into account our experimental results and chironomid larvae abundance in the lake during the study period (from 460 to 3,200 ind./m2), the authors conclude that larvae abundance did not limit the rate of their consumption in the lake by G. aequicauda, and one can consume up to 4 larvae per day. Thus, G. aequicauda could receive a diet of about 45% of their weight consuming about 2% of the available larvae daily in areas without the marine grass Ruppia thickets. In Ruppia thickets, chironomid larvae are not important food of G. aequicauda because the Ruppia leaves play a more important role in gammarid diet. With sufficient plant food resources, G. aequicauda can be successfully cultivated together with chironomid larvae.