Morphological diversity and differentiation of populations of Kamchatka ruver of chum salmon Oncorhynchus keta (Walbaum

A morphological study of nine samples from four Asian populations of keta of the rivers of Eastern Kamchatka: Avacha, Semlyachek, Zhupanova and Kamchatka was carried out. To quantitatively describe the appearance of chum salmon, a scheme was used that included the determination of 17 measurements. The magnitude of the Friedman test, determined for 17 measurements in nine samples, indicates statistically signifi cant heterogeneity between males and females. It is curious that, on average, for all measurements, the value of the Friedman test is higher in females than in males. This is most likely due to the higher variability of the body openings of females in diff erent populations compared to males. Among the measurements considered, the highest Friedman test scores are for measurements related to the location of the fins. Cluster analysis of the samples made it possible to distinguish two clusters among females: the fi rst includes samples from the Avacha and Semlyachek rivers and tributaries of the Kamchatka river — Andrianovka and Kozyrevka, the second group includes the Zhupanova river and tributaries of the Kamchatka river — the Kavycha, Klyukvenaya and Kimitina rivers. Samples of male chum salmon are divided into 2 clusters having the same sample composition. According to the modern ecogeographic zoning of rivers where Pacific salmon are caught, the Kamchatka River belongs to its region, the Semlyachek and Zhupanov rivers to the northeastern region, the Avacha River to the southeastern region. However, the samples we studied from these rivers do not form clasteres in accordance with the indicated zoning. Perhaps this is due to the presence of smaller ecogeographic units in each ecogeographic area, some have not yet been identifi ed. Infl uence of non-equilibrium sex ratio, loaded in a number of samples, is considered. Limiting for the eff ective size of the population is a small sex. Determination of the sex ratio during the spawning run should be included in the monitoring of the population size.