East Asia includes some of the countries with the highest domestic fisheries catch in the world, notably China and Japan. The status of their fisheries matters to the world because these countries also deploy huge fishing fleets into the high seas and the Exclusive Economic Zones of other countries, tasked with compensating for stagnating or even declining local fisheries resources.

Rebuilding East Asian fishery resources is a challenge, however, because their status is often unknown. This situation is due, at least in part, to the fact that time series of data suitable for analysis requiring sophisticated, but data-demanding methods, being scarce or not available in the region.

This dissatisfying state of affairs is now gradually being overcome, notably through the development, by Froese et al. (2017, 2018), of stock assessment methods that require less data, but still produce results that are reliable results enough to inform fisheries management.

These approaches consist of:

These methods were introduced to Chinese scientists via a highly successful training course held in Qingdao during June 16–20, 2019. The course was taught by the authors and Dr. M.L. Deng Palomares, with Dr. Rainer Froese participating remotely.

During the course, multiple stock assessments were run which eventually evolved into the bulk of the articles presented here. A few articles that were written previously and/or independently of the course are also included.

Altogether, 161 East Asian marine stocks were assessed, of which 132 pertained to finfishes and 29 to invertebrates, especially squids. Of these, 83 stocks were exploited along the coast of the Chinese Mainland (Liang, Xian, Pauly et al.; Liang, Xian, Liu et al.; Wang, Wang, Liu et al.; Wang X. et al.; Zhai and Pauly(a); Zhai et al.; Zhang L. et al.), 22 from around Taiwan (Ju, Chen et al.; Ju, Tian et al.; Liang Xian, Liu et al.), 50 around Japan (Liang, Xian, Liu et al.; Ren and Liu; Wang, Wang, Liang et al.; Wang, Liang et al.; Zhang S. et al.) and 6 around South Korea (Liang, Xian, Liu et al.).

As is the case for all stock assessment methods, the CMSY/BSM and LBB methods rely on reliable input data, i.e., catch (and catch-per-unit-effort) time series for CMSY/BSM and length-frequency data for LBB. Problematic inputs, and unrealistic constraints (“priors”) will lead to biased parameter estimates, and a few of the 161 estimates presented here will be biased up- or downward. However, there is no reason to assume a systematic bias.

Overall, these assessments jointly represent the most comprehensive evaluation of the Status of Marine Fisheries in East Asia, and they paint a very sobering picture. Thus, if one gives each stock a similar weight, one can compute from these assessments, for each region, the average biomass (or fish resource abundance) currently remaining as a percentage of its inferred biomass or abundance in the absence of fishing.

These mean percentages are 25% for the Chinese Mainland, 16% for Taiwan, 30% for Japan and 26% for South Korea; all of these averages are well below 50%, the level the classical stock assessment model of Schaefer (1954, 1957) requires for Maximum Sustainable Yield to be generated (Pauly and Froese, 2020). The regional means were derived from several ratio estimates that were higher, i.e., there are stocks in East Asia that are not overfished. However, there were far more stocks that had extremely low values of current to unfished biomass, with the result that the mean ratio for East Asia was 25%.

That overfishing is prevalent in East Asia was previously known (Srinivasan et al., 2012; Li et al., 2017). However, most of these assessments include estimates of the parameters also required to compute the time needed for overfished stocks to recover, given a reduction of fishing pressure (see Demirel et al., 2020). Thus, this makes it possible for fisheries scientists in East Asia to straightforwardly compute fishing quotas allowing for increasing stock sizes by a factor of two in the average, but which would allow for the social cost of a reduction of fishing effort to be smaller than the benefits gained from abundant stocks embedded in functioning ecosystems.

Indeed, at least for the Chinese Mainland, Zhai and Pauly(b) found, based on the conversion of 19 food web models into particle-size distribution spectra, that the functioning of coastal marine ecosystem of East Asia are gradually eroded due to the fisheries-induced disappearance of large fish species and miniaturization of the remaining species.

Thus, rebuilding stocks in East Asia would not only benefit fisheries economically, in terms of their catches, but also re-establish the functioning, rich marine ecosystems that enable fisheries to flourish in the longer term.