The baikal amphipod Gmelinoides fasciatus (Amphipoda, Crustacea) in the diet of perch in the littoral zone of Lake Onega (age and seasonal characteristics).
This paper focuses on the role of the invasive amphipod Gmelinoides fasciatus in the food web of Lake Onega, the northern range limit of the amphipod in the European part of Russia. Its significance as food is evaluated for the European perch Perca fluviatilis (L.) a populous fish species which is most common in the littoral zone of the lake. This invader is established to have become dominant in the diet of perch throughout the year. Its occurrence in the perch diet when the fish is 1-3+ years old averages about 80%, decreasing at older fish ages and being replaced by other representatives of the benthos, as well as by young fish. As to biomass, the role of the invader in the feeding of young perch (1-7+ years old) averages 50% (up to 79%, for 1-2+ years old) during the year. The percentage of invaders in the perch diet is decreased down to 3-10% with distance off the shore (at depths of more than 1.5 m). The introduction of G. fasciatus to Lake Onega is regarded to be positive, as it has increased the potential productivity of fishing in the lake.