Biological characteristics of smolts of European river lamprey Lampetra fluviatilis from the Chernaya River basin (Gulf of Finland, Baltic Sea)

Abstract

Smolts of European river lamprey Lampetra fluviatilis from the Chernaya River basin are described. Expansion of variation limits is suggested on the basis of comparative analysis of taxonomically significant characters of this population and the species area. Structure of gonads and intestine of specimens preparing themselves for the feeing phase of their life cycle is described and some changes during the feeding phase are reconstructed. The scheme of analysis and description of smolts is suggested, the last may be applied to other lamprey species. The term “smolt” is rightfully used for juvenile anadromous lampreys making downstream migration. Biology of parasitic nonanadromous species of lampreys during the feeding phase (juvenile postmetamorphic phase) differs from biology of smolts.