Interannual decrease in egg production index of western sand lance Ammodytes japonicus population in Harima-Nada, eastern Seto Inland Sea, Japan

Abstract

The reproductive potential of the western sand lance Ammodytes japonicus population during the spawning period (December–early January) was investigated based on egg production index (EPI) in Harima-Nada, eastern Seto Inland Sea for 13 years from 2008 to 2020. The EPI values showed a significant decrease since 2010 associated with decreasing density of western sand lance collected during the spawning period. Especially in the recent 5 years from 2016 to 2020, the values were much lower than those of previous years. The results indicate the critical decline in the total egg production of western sand lance in Harima-Nada. The EPI showed a significant positive correlation with total catch of age-0 western sand lance, suggesting that the EPI may be used to predict the western sand lance recruits.