SEASONAL VARIATION OF INVERTEBRATE ABUNDANCE AND DIET COMPOSITION OF ARCTIC CHARR IN AN ICELANDIC SPRING SYSTEM
The seasonal dynamics of invertebrate abundance and diet composition of fish as top predators were studied in the thermally stable environment of freshwater springs. We conducted a mark-recapture study on small benthic Arctic charr (Salvelinus alpinus) in the spring sources of a stream in South-Iceland, and sampled their stomach contents repeatedly over the course of a year. In addition, benthic invertebrate samples were taken at each sampling occasion to estimate the invertebrate availability in the habitat. Among a total of 635 processed fish, 55 were recaptured, some of them several times. Recaptured fish were usually re-captured at the same locations of the sampling area, which suggests site fidelity of fish in this system. Seasonal variation in invertebrate availability was reflected in the composition of prey items in the Arctic charr stomachs. While Chironomidae larvae were the most common prey items all year round, Plecoptera nymphs were most abundant in May, and Ostracoda and groundwater Amphipoda were more common during the wintermonths. The results indicate a clear seasonal shift in the diet of Arctic charr in the spring system, and lay the ground for future studies on spring food webs.
Agnes-Katharina Kreiling (Primary Presenter/Author), University of Iceland, email@example.com;
Eoin O'Gorman (Co-Presenter/Co-Author), University of Essex, firstname.lastname@example.org;
Jón S. Ólafsson (Co-Presenter/Co-Author), Marine and Freshwater Research Institute, Iceland, email@example.com;
Bjarni K. Kristjánsson (Co-Presenter/Co-Author), Hólar University College, Iceland, firstname.lastname@example.org;
Snæbjörn Pálsson (Co-Presenter/Co-Author), University of Iceland, email@example.com;