Based on length frequency data of miter squid (Uroteuthis chinensis) collected in the northeastern South China Sea in 1975–1977, 1997–1999, and 2018–2019, asymptotic length, optimal length at first capture, relative mortality, and relative biomass of the stock were estimated using length-based Bayesian biomass estimation (LBB). The LBB-estimated asymptotic length for 2018–2019 was smaller. Optimal lengths at first capture for the later far exceeded average lengths in catches because of a major increase in fishing intensity. Between 1975 and 1977, relative total mortality (Z/K) was low, but it increased in the latter two periods, while relative natural mortality (M/K) showed a downward trend. Relative biomasses (B/B0 and B/Bmsy) indicated that the stock was close to unexploited between 1975 and 1977, but they declined to the levels of 6% and 4% in the later periods, which correspond to growth in fishing horsepower. Indeed, by 2018, fishing horsepower increased by nearly four times the optimal level. The analysis suggests that the stock of miter squid has been overfished since the mid-1980s and is now under heavy fishing pressure. To recover the stock, it is imperative to reduce fishing intensity and enforce size-at-first-capture regulations.

中文翻译：

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使用 LBB 工具评估南海东北部的斜角鱿鱼种群

基于 1975-1977、1997-1999 和 2018-2019 年在南海东北部采集的斜角鱿鱼（Uroteuthis chinensis）的长度频率数据，其渐近长度、首次捕获最佳长度、相对死亡率和相对生物量使用基于长度的贝叶斯生物量估计 (LBB) 估计种群。LBB 估计的 2018-2019 年渐近长度较小。由于捕捞强度大幅增加，第一次捕获的最佳长度远远超过捕获的平均长度。1975年至1977年，相对总死亡率（Z/K）较低，但后两个时期有所增加，而相对自然死亡率（M/K）呈下降趋势。相对生物量（B/B0 和 B/Bmsy）表明，1975 年至 1977 年间，该种群接近未开发，但在后期下降到 6% 和 4% 的水平，这与捕鱼马力的增长相对应。事实上，到 2018 年，捕鱼马力增加了近四倍于最佳水平。分析表明，自 1980 年代中期以来，斜角鱿鱼的种群已被过度捕捞，现在正面临沉重的捕捞压力。为了恢复种群，必须降低捕捞强度并执行首次捕捞规模规定。