Feeding peculiarities of the juveniles of the Atlantic salmon (Salmo salar L.) infected with the invasive parasite Gyrodactylus salaris in the Keret River

Abstract

Extremely low feeding intensity was registered for the juveniles of Atlantic salmon inhabiting the Keret River (the White Sea basin) and infected with the invasive monogenean Gyrodactylus salaris. This was due to the asthenia observed during the summer period. The infected fingerlings and parrs were characterized by single specimens of the bottom invertebrates in their guts (larvae of caddis flies, nymphs of stoneflies and mayflies, and mollusks). The stomach filling index in these specimens was five to seven times lower comparing to the healthy individuals inhabiting the Ponoi and Kachkovka rivers (Kola Peninsula). About one-third of the infected fingerlings had empty guts, which was never observed for the juveniles of the wild populations of Atlantic salmon during the summer growth period in the rivers of Karelia and the Kola Peninsula.