Indices of reproduction for pink salmon Oncorhynchus gorbuscha of southeastern Sakhalin

Results of pink salmon monitoring in southeastern Sakhalin in 2003–2025 are presented, including data on their run abundance and biological parameters of spawners, the number of spawners on spawning grounds, and quantitative censuses of the downstream migrating juveniles in reference rivers. The downstream migration index (ratio of the number of downstream-migrating juveniles to the number of spawners in the rivers) and the return rate (the percentage of adult fish returning from the sea for spawning to the total number of wild and hatchery-reared juveniles migrating from the rivers) are calculated for all year-classes. The pink salmon groupings spawned in the rivers of the northern and central parts of the coast had similar inter-annual dynamics of landing, seasonal dynamics of runs, the body length and weight, fecundity of females, and dynamics of the downstream migration index and return rate that allows to consider them as a common stock of the southeastern coast of Sakhalin Island. The southern part of this coast is a transit zone for pink salmon running primarily to the rivers in the central part and partially southwestward, to the Aniva Bay.

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