The Infl uence of History of Using and Reproducing Biological Resources on the Contemporary State of Margaritifera margaritifera L. and Salmo salar L. Populations in the Northwestern Russia
The infl uence of the history of using and reproducing the biological resources on the populations of pearl mussel and salmon was studied from the example of the Kozha river (the Onega River basin). The pearl mussel was characterized by the low levels of density (0.09 ind./m2, on the average) and reproduction. The role of the anthropogenic factor for the population is negligible; the effect of the pealing is not observed. A reason for the slowed down reproduction of the pearl mussels is a drastic decrease in the number of Atlantic salmon in the Onega River basin in the late twentieth century. The second adverse factor is ths reconstruction of the Onega hatchery in 1984 with the transition to release juvenile salmon at the age of 1+. These measures have led to the termination of mollusk reproduction due to the fact that the density of juvenile salmons on the spawning-nursery grounds became below its critical level. For the preservation of the salmon population in the Onega basin, the artifi cial reproduction should develop; it is necessary to forbid fi shing the salmon, including fi shing on the ways of its migration (except for catching for needs on the hatchery and traditional craft in distant settlements).