Stomach content of whitefish, Coregonus lavaretus (Actinopterygii: Salmoniformes: Salmonidae), off the Åland Islands, Baltic Sea

The Aland Islands are major feeding grounds for threatened whitefish, Coregonus lavaretus (Linnaeus, 1758), in the Gulf of Bothnia, Baltic Sea. Diet of the foraging whitefish, however, has been poorly studied in this area. In the presently reported spot-check study we analysed stomach content of whitefish (n = 88), sampled by gillnets at hard bottom shallows during spring and summer (June-August) 2012. Molluscs and benthic crustaceans were the main prey items, where the rank order of abundance and biomass of food items was Theodoxus fluviatilis > Idotea spp. > Gammarus spp. > Hydrobia spp. > Mytilus trossulus > Radix spp. A shift towards T. fluviatilis was observed from June to July-August. The acquired knowledge on the diet composition could help to shed more light on the ecology of whitefish in the Baltic and may serve to indicate food web alterations due to climate variations and long-term change.