Sockeye salmon of Itupup island. 1. New status data populations in lakes Sopochnoe and Krasivoe

Abstract

   The aim of the work is to present the first data on the size and age characteristics of juveniles and adults of sockeye salmon in the lake Sopochnoye in comparison with the data characterizing the juveniles and adults of sockeye salmon in the lake Krasivoye.
   The material of the study was the collection of juveniles and adults of sockeye salmon from lakes Sopochnoye and Krasivoye, obtained in the course of various studies in the period from 1995 to 2020.
   Methods used: comparative data analysis, descriptive statistics methods.
   Results. It was established that most of the juvenile sockeye salmon from both lakes migrated to the sea at the age of 1+, and most of the adults belonged to two age groups — 1.2+ and 1.3+. The share of fish of these groups was 80.0 % in the lake Krasivoye and 89.7 % — in the lake Sopochnoe. Three more age groups — 1.4+, 2.2+ and 2.3+ were represented symbolically. At the same time, in the population of lake Krasivoye 85.0 % of all individuals, both males and females, spent only two years at sea. The proportion of such fish in the lake Sopochnoe was also significant — 35.9 %, but most of the producers spent a year longer at sea. The mass of females and males in the first of the lakes averaged 2.01 and 2.18 kg, and in the second 1.76 and 2.11, respectively.
   Practical significance. Since almost all sockeye salmon from the lake Krasivoye and Sopochnoye migrates to the coast at the age of 1+, and with rare exceptions (both females and males) spends only 2–3 years in the sea, it can be characterized as relatively early maturing. This fact significantly increases the attractiveness of Iturup Island sockeye salmon as a potential object for artificial reproduction.