Evaluating Stock Status of 16 Commercial Fish Species in the Coastal and Offshore Waters of Taiwan Using the CMSY and BSM Methods

Abstract

The waters around Taiwan are impacted by the Kuroshio and coastal currents, resulting in a high productivity and a high diversity of marine life. As a consequence, there are a multitude of fisheries around Taiwan, conducted by a fleet that has grown enormously in the last four decades. Here, we investigate the effect of the resulting fishing pressure on 16 commercial fish stocks including demersal and pelagic species in the coastal and offshore waters of Taiwan using the Monte Carlo Catch-Maximum Sustainable Yield (CMSY) and Bayesian Schaefer Model (BSM) methods. Both of these methods required principally catch time series, with the BSM methods also requiring catchper-unit-of-effort data. The results show that of the 16 assessed stocks, 10 stocks have collapsed, 2 are severely overfished, 2 are overfished, 1 is slightly overfished, and only 1 stock remains in a healthy status; these troubling results are attributed to excessive fishing pressure. However, climate-driven environmental variability may be another factor affecting the fishery resources around Taiwan, as evidenced by chub mackerel Scomber japonicus, the one stock deemed healthy, which is here attributed to favorable environmental condition. Using the fisheries reference points provided here, rebuilding plans could be provided for the other 15 species; however, such plans are not likely to be successful without reducing the size of the Taiwanese fishing fleet.

Assessing Summertime Primary Production Required in Changed Marine Environments in Upwelling Ecosystems Around the Taiwan Bank

“…By 2018, it had decreased to 16% (Figure 2). This dramatic decline can be attributed to high demand, unregulated fishing practices, and overexploitation [20,21]. In their evaluation of the stock status of 16 species under fishing pressure in the waters surrounding Taiwan, Ju et al [21] discovered only one species that is not overfished.…”

“…This dramatic decline can be attributed to high demand, unregulated fishing practices, and overexploitation [20,21]. In their evaluation of the stock status of 16 species under fishing pressure in the waters surrounding Taiwan, Ju et al [21] discovered only one species that is not overfished. Furthermore, climate-driven environmental variabilities such as the El Niño-Southern Oscillation (ENSO) are pivotal factors affecting the intensity of the upwelling regions in the TB.…”

Stock Assessment of 19 Perciformes in the Beibu Gulf, China, Using a Length-Based Bayesian Biomass Method

“…Recently, two methods have been applied to the assessment of fishery resources in China. One is the maximum sustainable yield (MSY) model, which uses a time series of catch and auxiliary data to estimate the MSY (Ju et al, 2020b;Liang et al, 2020;Zhai et al, 2020); The other is the length-based Bayesian biomass (LBB) model, which uses length frequency (LF) data to estimate asymptotic length, length at first capture, relative natural mortality and relative fishing mortality (Ju et al, 2020a;Kindong et al, 2020;Liang et al, 2020;Zhang et al, 2020Zhang et al, , 2021. Size measurement is the basic requirement for marine fishery resource surveys in China (Jin et al, 2012), and LF data are usually easier to obtain and cheaper than other data types (Liang et al, 2020).…”

Distribution and Catch Rate Characteristics of Narrow-Barred Spanish Mackerel (Scomberomorus commerson) in Relation to Oceanographic Factors in the Waters Around Taiwan

“…Moreover, the fluctuation of these currents is strongly influenced by the seasonal monsoons and varied topography; consequently, the currents change the oceanographic conditions in the WT in different seasons (Lan et al, 2020b;Tseng et al, 2020). Biogeographically, the Taiwan Strait (TS) and waters off eastern Taiwan are migration routes for numerous pelagic fish species; therefore, their ecosystem dynamics and biogeochemical and physical processes vary substantially in space and time (Liao et al, 2018;Ju et al, 2020;Lin et al, 2020). The WT constitute excellent spawning, feeding, and overwintering habitats (Hsu et al, 2007;Madigan et al, 2016;Hsiao et al, 2021).…”

“…This dramatic decline might be due to the high demand, unregulated fishing practices, or overexploitation of these species. Ju et al (2020) evaluated the stock status of S. commerson under fishing pressure in the WT and found that three stocks had collapsed. S. commerson species were classified as highly susceptible to the high levels of exploitation in the waters off eastern Taiwan (Lin et al, 2020).…”