The ecology of the freshwater form of the Atlantic salmon Salmo salar L., the brown trout Salmo trutta L., and the freshwater pearl mussel Margaritifera margaritifera L. in Syuskyuyanyoki River (Basin of Lake Ladoga)

The locations and the area of the spawning–growing grounds have been assessed in the Syuskyuyanyoki River (the basin of Lake Ladoga), as has the population density of the juveniles of the freshwater form of the Atlantic salmon and the brown trout. The Atlantic salmon spawns at present on the rapids downstream of the hydroelectric power plant because of the insurmountable dam; the population density of this species has decreased dramatically. Only the landlocked form of the brown trout was found; the anadromous form was not. The brown trout has resettled along the major part of the river. We suggest that there are two subpopulations of the freshwater pearl mussel that differ with regard to the host for their larvae. The intensity of invasion of the juveniles of salmonids by the larvae of the freshwater pearl mussel and the survivability of glochidia did not depend on the host species. The growth rate of the mollusks and the age–size structure of the freshwater pearl mussel population have been assessed.