Environmental factors influencing inshore migration in Japanese eel Anguilla japonica

Abstract

Catadromous eel species of the genus Anguilla have a long and complex life history, migrating between offshore spawning areas and continental growth habitats. The eel larvae are passively transported, metamorphosing into glass eels and colonizing continental growth habitats. However, inshore migration and recruitment mechanisms need to be better understood, notwithstanding the increasing concern for sustainable future stock. Inshore migration of glass eel, Japanese eel Anguilla japonica, concerning regional environmental factors, examined throughout the year in central Japan facing the Pacific Ocean. A total of 3534 glass eels were collected through 33 investigations, with peak recruitment occurring from February to April. The inshore migration occurred for both new and full moon phases during ebb tide, with mean daily temperature ranging from 5.8 to 23.3 °C. In various environmental factors, a clear recruitment peak was found at the timing of westerly wind, with a significant positive correlation between wind speed and CPUE (catch per unit effort). Westerly wind advects the surface seawater towards the coastal area, and the stronger wind facilitates the inshore migration of glass eels to continental habitats. Understanding the reliable environmental factors affecting the inshore migration of Japanese glass eels can help facilitate the management and conservation of regional eel stocks.