Features of the spatial distribution and size structure of the Pacific lamprey <Emphasis Type="Italic">Lampetra tridentata</Emphasis> in the North Pacific

Results of long-term research on the spatial and vertical distribution of the Pacific lamprey Lampetra tridentata (Richardson, 1836) (the family Petromyzontidae) in the North Pacific, and data on its size structure are submitted. It was shown, that L. tridentate reached its greatest number in the Bering Sea. The maximum concentration of the Pacific lamprey was observed all year round about Navarin Cape, in the Koryak shelf area, at the East Aleutian Islands and at the west coast of the USA, which, apparently, spoke of the increased number of its prey there. On the bottom, the Pacific lamprey was the most numerous at depths of less than 500 m, and in the pelagic, in the upper 100-meter layer. The length of individuals varied in catches from 12 up to 85 cm. The existence of several size groups may indicate that the Pacific lamprey spend several years in the sea. No correlation was revealed between the length of body and fishing depth. The correlations between body length and body weight, body length and condition factor were analyzed. Seasonal dynamics of these parameters were considered.