Characteristics of adult chum salmon Oncorhynchus keta from the commercial stock at Iturup Island in 2023

Abstract

Adult chum salmon Oncorhynchus keta specimens returning to spawn were caught in the Prostor and Kurilsky Bays of Iturup Island and examined in the period from September 18 to October 31, 2023. The males dominated among sexually mature or close to sexually mature individuals; the portion of females had a tendency to increasing from the beginning to the end of the run. Most of the fish were aged 3+ (76.8% and 77.9% on average in the Prostor and Kurilsky Bays, respectively), the average portion of fish at the age 2+ was 10.6% and at the age 4+ and 5+ — 12.0 %, although the portion of three-year-old fish varied very much between the samples that was not observed in previous 10 years. The weight of adult chum salmon in corresponding age groups was similar in these two bays, on average 2.47 and 2.72 kg for females and males at age 3+, respectively, that was slightly below the values in previous 9 years.