Patterns of Downstream Migration of Pink Salmon Oncorhynchus gorbuscha in the Malaya Khusi River (Sakhalin Oblast)

Abstract

Patterns of downstream migration of juvenile pink salmon Oncorhynchus gorbuscha in the Malaya Khusi River (northeast of Sakhalin island) are revealed as a result of observations conducted in 2014–2017. Downstream migration starts in May when water is warmed up to 4–5°С. The bulk of fish migrates seaward at 5–10°С. The duration of downstream migration is ~2.5 months. Downstream migration is confined to nocturnal period. Downstream migrants are distributed predominantly in the meadstream, at the line of fastest flow. Some species-specific mechanisms of downstream migration are made clear. The total number of pink salmon downstream migrants during the period of observations is calculated.