Features of Spatial Structure of Mikizha Parasalmo mykiss in the Kol River, Western Kamchatka: On the Problem of the Population Integration in the Complex River System

Resumo

The features of within-river migrations, biological and morphological characteristics, and allozyme variation are studied in mikizha Parasalmo mykiss in the Kol River basin, Western Kamchatka. In this river system with a complex geomorphology, mikizha spawns in tundra-type tributaries, and each tributary is characterized by a certain combination of size, water content, hydrological, and thermic regime. Therefore, the spawning conditions, as well as spatial distribution and biological characteristics of the progeny, are variable. Based on the mark-recapture data, mikizha intensively migrates within the river system, and it does not show any fidelity to certain sites; the spawners can enter different tributaries in various years. Based on the variation of morphometric characters, the difference between the juveniles from various tributaries is absent. The results of allozyme variation show that, despite a mosaic structure of the habitats, mikizha of the Kol River is represented by a single population with a common genofond. Based on the results of this study, it is concluded that mikizha of the Kol River is a single and highly integrated population despite the factors facilitating the diversity. A mechanism of a stable population unity is connected with the within-river migrations, and the spawners are redistributed in different tributaries of the river during each year. This redistribution is directed against the founder effect and gene drift.