Abstract
Iturup Island (in southern Kuril Islands) and southeastern Sakhalin Island are known by the highest catches of salmons within the Sakhalin-Kuril region. The timing of pink salmon mass return to Iturup is 5–10 days later than to Sakhalin, and the females returned to Iturup have higher relative individual fecundity, on average. In 2014, an unexpected increase of pink salmon catches occurred on southeastern Sakhalin Island, with a simultaneous sharp decrease of the catches on Iturup Island. Assumption on appearance of Kuril pink salmon in the Sakhalin waters was confirmed by analysis of the scale parameters (number of sclerites and intercirculi distance in the first-year scale zone), dynamics of catches, and individual fecundity of females. Sharp opposite changes of the pink salmon catch dynamics were noted again for these areas in 2017 and 2018. Such changes of pink salmon abundance could be reasoned by environmental conditions of reproduction in these areas or new redistribution between two areas. To clarify the issue, complex analysis (same as for 2014) was applied for pink salmon at southeastern Sakhalin and Iturup in 2017 and 2018 (187 and 215 fish samples from Sakhalin and 194 and 152 fish samples from Iturup in these two years, respectively). The results were interpreted following the hypothesis of fluctuating stocks. Taking into account the complex of traits, there is concluded that the assumption about redistribution of pink salmon between southeastern Sakhalin and Iturup Island in 2017 and 2018 is untenable.
Highlights
Iturup Island and southeastern Sakhalin Island are known by the highest catches of salmons within the Sakhalin-Kuril region
In 2014, an unexpected increase of pink salmon catches occurred on southeastern Sakhalin Island, with a simultaneous sharp decrease
Assumption on appearance of Kuril pink salmon in the Sakhalin waters was confirmed by analysis of the scale parameters, dynamics of catches, and individual fecundity of females
Summary
СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА РОСТА ЧЕШУИ У ГОРБУШИ ИЗ ВОЗВРАТОВ НА ОСТРОВА САХАЛИН (ЮГО-ВОСТОЧНОЕ ПОБЕРЕЖЬЕ) И ИТУРУП В 2017 И 2018 ГГ. На Итурупе (южные Курильские острова) и юго-восточном побережье о. На юго-восточном побережье Сахалина и в эти же годы у 194 и 152 рыб на о. Taking into account the complex of traits, there is concluded that the assumption about redistribution of pink salmon between southeastern Sakhalin and Iturup Island in 2017 and 2018 is untenable. Итуруп (южные Курильские острова) и юго-восточное побережье Сахалина характеризуются исторически наиболее высокими уловами горбуши в Сахалино-Курильском регионе по отношению к протяженности береговой линии. Уловы горбуши в сравнении с родительским поколением на юго-восточном побережье Сахалина неожиданно увеличились с 28,4 до 41,9 тыс. Т, а на юго-восточном побережье Сахалина уменьшились до 4,5 тыс. Тем не менее нельзя исключать возможность очередного перераспределения рыб между разными районами своего нереста, в связи с чем предпринято изучение характеристик роста чешуи у горбуши в возвратах в данные районы в 2017 и 2018 гг. с целью подтверждения или опровержения рабочей гипотезы
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