Updated stock assessment of Japanese eels using Japanese abundance indices

Abstract This paper updates the stock assessment of Japanese eels Anguilla japonica in East Asia (Tanaka in Fish Sci 80:1129–1144, 2014) using the previous method of the maximum likelihood estimation with the same dynamical models of stock abundance and adding new available data since 2011. The data for estimations include catch history in East Asia (1894–2022) and standardized catch per unit effort of commercial fishery for the exploitable stock (1954–2006 and 1968–2008) and glass eels (1954–2022, 1972–2004, and 1973–1977). From the results of the base case scenario of the estimations, the estimated stock size of individuals aged 1 year and older was 21 thousand tons in 2023, which was 28% of the carrying capacity. The estimated stock size has recovered since 1990. The estimate of the maximum sustainable yield was 4440 tons if only the exploitable stock was utilized and 282 tons if only the glass eel was utilized. That of the sustainable yield as allowable biological catch for glass eels in 2022 was 129 tons, which was greater than the actual catch record (60 tons). The paper further discusses these results and issues relating to estimation and management for reducing the impact on the stock.