Estimation of abundance for migrating juvenile pink salmon in the rivers of Sakhalin and Iturup Islands in 2023

Abstract

Number of juvenile pink salmon migrated from the spawning grounds in the rivers of East Sakhalin (Dagi, Malaya Khuzi, Kholodny (tributary of Poronay), Lazovaya, Pugachevka, Voznesenka, Ochepukha, Taranai, and Kura) and Iturup Island (Rybatskaya and Olya) was assessed. The downstream migration index was calculated for each of these rivers as the ratio between the number of spawners entered the river and the number of juveniles migrated down. The number of wild pink salmon juveniles from all rivers of the islands was evaluated separately for several local stocks spawned on East Sakhalin and the stock spawned on Iturup Island on the data of pink salmon spawners number for each local stock and the downstream migration index determined for the abovementioned control rivers. The total number of the fry migrated from the rivers of East Sakhalin in 2023 was assessed as 848.0∙106 ind. and from the rivers of Iturup — as 265.4∙106 ind. In addition to wild ones, the fry was released from salmon hatcheries located on East Sakhalin (145.1∙106 ind.) and Iturup Island (152.5∙106 ind.).

Keywords

• sakhalin
• iturup island
• pink salmon
• downstream migration
• juveniles abundance
• downstream migration index