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August 16, 2025Open Access

A decade after being listed as Endangered: Japanese eel stock inferred from fishery-dependent and independent monitoring records (Preprint)

Key Points

Substantial declines in yellow and silver eel populations were observed, indicating a loss of abundance over the past decade.
Catch-per-unit-effort data indicated reductions of 79.2% to 99.9% in seven out of eight datasets available for analysis.
The study integrated new freshwater data and scientific monitoring to enhance reliability of the population indicators.
Findings highlight urgent conservation needs for endangered species like the Japanese eel, calling for effective management strategies.

Abstract

Abstract This study assesses recent trends in the abundance of Japanese eels ( Anguilla japonica ), which have been listed as Endangered on the IUCN Red List of Threatened Species since 2014, by updating previously reported coastal fisheries datasets and incorporating new freshwater data and scientific monitoring records for glass eels in Japan and Taiwan. Catch-per-unit-effort (CPUE) data for yellow and silver eels revealed statistically significant declines in seven of eight datasets, with projected reductions over three generations (24 years) ranging from 79.2% to 99.9%. In contrast, no significant temporal trends were detected in the CPUE of glass eels, likely due to high interannual variability driven by oceanic conditions. The integration of freshwater and coastal data, along with fishery-independent monitoring, enhances the reliability of these indicators. The results provided in this study represent the best currently available indicators of Japanese eel population dynamics.

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