Habitat use of Japanese eel, Anguilla japonica, in brackish water lake, revealed by acoustic telemetry

Abstract

The Japanese eel, Anguilla japonica, is one of the most important fishery species in Japan, however, population of this species has been decreased, with the species listed as endangered (EN) on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. To investigate habitat use of Japanese eel inhabiting brackish water lake, behavior of 10 individuals were monitored using acoustic biotelemetry. Eels with ultrasonic transmitter were released into study area that included rock revetment area, reed area, concrete revetment area and offshore. Acoustical signals were received by 14 receivers and position of each individual was estimated when possible. Signals were recorded more frequently in the night time than in the day time, indicating nocturnal behavior of this species. Some eels spent longer time near shore but others spent most of time offshore, and we could not find any clear tendency shared by the majority of the eels tested in this study. For about eels that used shore area, rock revetment area appears to be preferred than reed or concrete revetment areas. The results obtained in this study indicate that Japanese eels inhabiting brackish water lake utilize both shore and offshore areas.