Assessment and management recommendations for the status of Japanese sardine Sardinops melanostictus population in the Northwest Pacific

Abstract

Japanese sardine (Sardinops melanostictus) is one of the main species caught in the high seas purse seine fishery in the Northwest Pacific Ocean and its resources gradually recovered in recent years. This paper used the historical yearly catch data of Japanese sardine from 1990 to 2021 and biological data (manily for body length) in April-November 2020–2022 to assess its maximum sustainable yield (MSY) and stock resource status using Catch-MSY and LBB models, respectively. And then based on the evaluation results of Japanese sardine MSY, we analyzed the stock management strategies on this species by the Kobe II Strategy Matrix (K2SM). The results were as follows: (1) the Catch-MSY model assessed its MSY as 170.0 × 104 t with a 95 % confidence interval of 134.1 × 104 t ∼ 211.4 × 104 t; (2) the LBB model assessed the biological parameters for the last three years (2020–2022) with the interval range of Lc/Lc_opt was 0.76–0.95, B/BMSY was 0.79–0.84, and B/B0 was 1.9–2.3, which indicate that Japanese sardine resource is healthy and recovering; (3) the results of these two models and the Kobe Ⅱ management strategy matrix are combined to predict future resource status probability values. The management target range for the medium term (5-10 years) should be set 100 % TAC to MSY values, i.e., 102.0 × 104 t–170.0 × 104 t as TAC, and for the long term (10–20 years) can be set to 120 % TAC to MSY values, i.e., 122.4 × 104 t–170.0 × 104 t. Japanese sardine fishery resource can be sustainably used on a longer time scale.