Stock Status Assessments for 12 Exploited Fishery Species in the Tsushima Warm Current Region, Southwest Japan and East China, Using the CMSY and BSM Methods

Abstract

This contribution presented stock assessments for 10 fish and 2 squid populations exploited by Chinese, South Korean, and Japanese fishing fleets in the Tsushima Warm Current region, i.e., Southwest Japan and East China. The methods used were a Monte Carlo method (CMSY) and a Bayesian state-space implementation of the Schaefer model (BSM), based on published time series of catch and abundance data (SSB and CPUE). Results showed that 2 fish stocks, Japanese jack mackerel (Trachurus japonicus) and yellowback sea-bream (Dentex hypselosomus), had a healthy status, while daggertooth pike conger (Muraenesox cinereus) appeared to have collapsed. The other 9 stocks showed varying degrees of overfishing. The cooperation of several countries would be required to recover the fishery resources in the Tsushima Warm Current region.

Commentary: Stock Status Assessments for 12 Exploited Fishery Species in the Tsushima Warm Current Region, Southwest Japan and East China, Using the CMSY and BSM Methods

“…Such a comprehensive review is a valuable trial for East Asian countries, as the beginning toward modern fisheries stock assessment and management. We also agree with one of the main conclusions drawn by Wang et al (2020b) (hereafter "WA2020"), emphasizing the importance of close cooperation among East Asian countries for stock assessment and management.…”

“…(A) shows stocks which the selection of abundance indices leads to misunderstanding of current stock status, and (B) shows stocks which the selection of abundance indices does not affect the current stock status estimation, but still leads to different view of past trajectories. We found such insufficient use of abundance indices in seven stocks by Wang et al (2020b), but could re-produce the same results for only six stocks as shown above.…”

“…The numbers shown are the estimates of B/Bmsy and F/Fmsy for the most recent year available. The percentage shown are the percentage difference between Wang et al (2020b) and this study using extended timeseries. (A) shows stocks which the selection of abundance indices leads to misunderstanding of current stock status, and (B) shows stocks which the selection of abundance indices does not affect the current stock status estimation, but still leads to different view of past trajectories.…”

“…For example, 1973-2017 data is available for T. japonicus in the referred Japanese report (Yoda et al, 2019), whereas WA2020 only used the 1996-2017 data. The arbitral data usage resulted in misunderstanding of historical trends of the six stocks Wang et al (2020b) and the black solid lines show the estimates when the same method was applied to all available abundance indices. The numbers shown are the estimates of B/Bmsy and F/Fmsy for the most recent year available.…”

“…Wang et al (2020b) used only part of the available abundance indices (shown in gray cross marks in the figures on the left) from the referred literature (shown by the black solid line in the figures on the left). The gray crossed lines show the estimate of B/Bmsy (figures in the middle) and F/Fmsy (figures on the right) byWang et al (2020b) and the black solid lines show the estimates when the same method was applied to all available abundance indices. The numbers shown are the estimates of B/Bmsy and F/Fmsy for the most recent year available.…”