Management of glass eel fisheries is not a sufficient measure to recover a local Japanese eel population

Abstract

We evaluated whether a strict fisheries management measure of closure of fishing for recruiting juveniles (glass eels) could have resulted in the recovery of a local population of Japanese eels, Anguilla japonica, when there was no harmonized management of the other life stages, the relevant ecosystem, or local socioeconomic factors (i.e., Ecosystem-Based Management (EBM) approach not applied). The study was conducted in the Kojima Bay-Asahi River system, Okayama Prefecture, Japan, because this prefecture has not permitted commercial glass eel fisheries since 2003, which provides a unique opportunity to conduct a quasi–experimental evaluation of the effects of a glass eel fisheries moratorium. Longline eel fishery data and fishery-independent sampling data indicate that growth-phase Japanese eel (yellow eel) abundance in this water system has not increased, or maybe even decreased, since commercial glass eel fisheries in this area were closed. Based on the results obtained in this study, we concluded that the closure of glass eel fisheries was not a sufficient countermeasure to recover the Japanese eel population in the study area. To conserve and sustainably use Japanese eels, a series of management measures such as habitat restoration and management of yellow and silver eel fisheries are needed along with the control of glass eel fisheries throughout the species distribution range. The EBM approach might be helpful to progress integrated management at appropriate spatial scales.