Relationship between coastal water properties and adult return of chum salmon (Oncorhynchus keta) along the Sanriku coast, Japan

We investigated the relationship between adult (age‐4) return rates for chum salmon ( Oncorhynchus keta ) originating from the Iwate Prefecture, Japan, and coastal environmental conditions during their early ocean life in coastal residency. We analyzed distributions of water properties via intensive hydrographic observations using a conductivity–temperature–depth profiler. Both the return rates and water properties vary strongly over interannual time scales. We found that the time when the return rate decreased drastically corresponded well to the time when the frequency of warm waters in the coastal residency increased.