Seaward migration of pink salmon Oncorhynchus gorbuscha (Walbaum) fry in the Malaya Khuzi River (North-Eastern Sakhalin) in 2018

Abstract

Counting pink salmon Oncorhynchus gorbuscha fry, migrating seaward in the Malaya Khuzi River (NorthEastern Sakhalin), revealed the total half-million stock of the migrants in 2018. Forming such generation from extremely poor parental stock, entered the river in 2017 had been possible due to a high survival rate in the course of incubation. Seaward migration was about 1.5 month long and finished 7–10 days earlier than in previous years. Major part of the fry stock emigrated during the I decade of June. Dense aggregations of ice on the seashores during the mass seaward migration could bring negative effects on survival of the fry. Migration occurred at night. Day time migration was observed in case of decreasing water transparency on flooding. The migrants in most cases did not have yolk sack residuals. Mean values of the body length and weight of the migrants did not exhibit extensive changes for the period of migration.