[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.

[Peculiarities of the parasitofauna of Atlantic salmon parr (Salmo salar L.), brown trout (Salmo truttae L.), and char (Salvelinus alpinus L.) in the Utsjoki River system (Northern Finland)].

Data on the parasite diversity in Salmonidae fish parr from different parts of the Utsjoki River obtained during 1993-1995 and 2006-2007 are presented. Three fish species, Salmo salar L., S. truttae L., and Salvelinus alpinus L., were examined on the presence of helminthes. Twenty species of salmon parasites were found, the majority of which are the parasites with complicated life cycles. Infusorians C apriniana piscium, myxosporidia Chloromyxum januaricus and Myxobolus neurobius, metacercaria of the genera Diplostomum and Apatemon, and the nematode Raphidascaris acus larvae were the most numerous in salmon parasite fauna. Brown trout had the most number of specific parasite species, whereas char was infested by protozoan parasites only.

[Population dynamics of glochidia of the freshwater pearl mussel Margaritifera margaritifera L., parasitizing on juvenile Salmonidae fishes in northern water reservoirs].

This paper presents data on the population dynamics of glochidia of the freshwater pearl mussel Margaritifera margaritifera L. (1758) (a declining species of European fauna), parasitizing on juvenile Salmonidae fishes in rivers of northern Europe. It was found that the number of glochidia parasitizing on gills of juvenile salmon and trout in explored water reservoirs are stimulated by negative binomial distribution. Estimation of the distribution parameter allows us to obtain statistically valid data on the population number of pearl mussel and to judge the stable character of interactions in the host-parasite system (balance of host specimens that are resistant and nonresistant to infection).

[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.