Active feeding of anadromous white-spotted char Salvelinus leucomaenis at the southern latitudinal rivers

Abstract

Although starvation poses a serious risk of death, it is a common phenomenon among anadromous salmonids that fast after returning to the river following oceanic feeding migration. To address the effects of geographic environmental factors on their feeding, we examined the river feeding patterns and condition of sea-run migrants of white-spotted char ( Salvelinus leucomaenis) in rivers with latitudinal variation from 38°N to 46°N along the Sea of Japan. The river feeding patterns showed a significant latitudinal trend: char were observed to feed at lower latitudes and fast at higher latitudes. In contrast, the condition factor did not exhibit any latitudinal trends. These findings suggest that the environmental conditions encountered by individuals prior to and after river entry may influence their river feeding. Active feeding by the southern sea-run migrant char may be an adaptive strategy to maintain their body condition in response to the local conditions. This study highlights the importance of rivers not only as spawning and growth habitats for juveniles, but also as feeding habitats for certain anadromous salmonids.