[Peculiarities of the biology and parasite fauna of juvenile Atlantic salmon (Salmo salar L.) in the Pista River (White Sea Basin), according to the Gyrodactylus salaris infestation].

Juvenile salmon Salmo salar m. sebago Girard from the Pista River system (the White Sea Basin) was investigated. The data on species composition and occurrence peculiarities of Gyrodactylus salaris Malmberg, 1957 are given. This monogenean is the alien species for the river system and it is recorded for the first time. It is shown that the distribution of the parasite abundance is can be described as the negative binomial distribution; variations of its parameters (k and p) were also characterized. Parasitological data obtained, as well as the data describing the characteristics of growth and age structure of juvenile salmon population, suggest the potential influence of G. salaris infection on the degree of survival of fishes in the lake-river system examined.

[Long-term changes in the epizootic of juvenile salmon (Salmo salar L.) in the Keret River (White Sea basin) depending on the invasion of Gyrodactylus salaris Malmberg, 1957].

Results of long-term investigations on the population dynamics of juvenile Atlantic salmon (Salmo salar L.) in the Keret' river (White Sea drainage basin) depending on the invading of Gyrodactylus salaris (Malmberg, 1957) and mass infestation of salmon with this parasite are presented. Gyrodactylus salaris was for the first time recorded in the Keret' river in 1992. During the period lesser than five years the parasite spread along the river. The rise in the infestation of salmon parr with G. salaris caused death of the fish host. As the abundance of juveniles decreased, adult salmon stocks dropped more than 25 times. It was shown, that after the decreasing in number of salmon juveniles following acute epizootic, infestation parameters dropped, and in some years G. salaris was not even found at all.

[Parasite fauna of young landlocked salmon (Salmo salar m. Sebago girard) in the Pista River (the White Sea Basin)].

A native population of landlocked salmon of the Pista River was investigated in 2000-2002. Adult salmon in Pista River has smallest size among other populations of landlocked salmon in Karelia. Data on the biology and parasite fauna of young salmon are presented. The presence of local salmon populations in lakes of the river system is apparently one of the mechanisms keeping the magnitude of population. The presence of Gyrodactylus salaris, a harmful parasite of the young landlocked salmon, is established in this territory for the first time. This monogenean species is believed to have been introduced into the Pista River via stocking from Finland.

[Seasonal dynamic of the infestation of young landlocked salmon (Salmo salar morpha sebago, Girard) by the monogenean species Gyrodactylus salaris].

Seasonal dymanic of the infestation of young landlocked salmon (Salmo salar morpha sebago, Girard) by the monogenean species Gyrodactylus salaris Malberg, 1957 was studied in the river Lizhma, Karelia. It is established, that the temperature optimal for the development and reproduction of the parasite is about 3-8 degrees C. It is stated, that the abundance of G. salaris in the river Lizhma do not reach so high values, as it was observed in the regions outside the natural area of the parasite.