2025/07/03 by Ayano Medo, Daichi Kojima, Toshihiro Wada +3 · 1 voice
Environmental Science · Agricultural and Biological Sciences · #Fish Ecology and Management Studies #Aquaculture Nutrition and Growth #Fish Biology and Ecology Studies
paper · doi:10.3354/meps14928
openalex publication_date 2025/07/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/11
Partial migration, whereby some individuals migrate to non-natal habitats while others remain in natal habitats, can be maintained by trade-offs between survival and fecundity potential. The Japanese seabass Lateolabrax japonicus is a marine-spawning carnivorous fish that exhibits partial migration, with some juveniles and adults migrating to rivers in spring and summer and returning to the sea in winter. Given the minimal differences in growth rate at maturity between marine residents and river migrants, resource partitioning within a contingent is a potentially important factor in maintaining the river migrants. This study examined differences in feeding ecology, specifically trophic niche width and individual specialization, between marine residents and river migrants of Japanese seabass from Tango Bay and the Yura River using stable isotope analysis of multiple tissues. Stable carbon and nitrogen isotope ratios (δ 13 C and δ 15 N) of muscle and liver tissues, which reflect long- and short-term dietary information, were used to estimate trophic niche width and individual specialization. Trophic niche overlap rates between marine residents and river migrants were 17.5% for adults and 0% for juveniles in muscle tissues, suggesting niche partitioning between contingents. Total niche width was larger in river migrants than in marine residents, with individual specialization observed only in river migrants. These findings indicate that individual specialization among river migrants may enhance resource availability within contingents, reducing density dependence in the more resource-limited river habitats.