东海带鱼的最适可捕规格

带鱼是中国东海的重要经济渔获种类,其可捕规格会随不同时期的捕捞强度而变化。为确定目前东海带鱼最适可捕规格,根据2016—2020年拖网、帆张网及延绳钓等主捕带鱼作业方式采集的带鱼样品和数据,利用FiSAT II软件对其生长、死亡参数进行估算,进而计算可捕规格。结果表明: 带鱼的拐点肛长、临界肛长、1龄鱼肛长分别为382.84、397.12、216.05 mm,50%带鱼性成熟肛长为230.38 mm,最小可捕肛长为219.23 mm。利用Beverton-Holt模型分析带鱼单位补充量渔获量可知,带鱼当前渔业参考点为:t_c=0.38 a,F=2.11,处于捕捞过度区域,并得出最适可捕肛长为364.64 mm。但过高的可捕规格会导致短期内带鱼产量急剧下降,渔民难以接受,因此,本研究综合考虑采用接近1龄鱼肛长与50%性成熟肛长作为最适可捕规格较为合适,即220 mm。

Optimum capture size of Trichiurus japonicus in the East China Sea

Trichiurus japonicus is an economically valuable species in the East China Sea, whose allowable capture size varies with fishing effort in different years. To clarify the optimum capture size for T. japonicus in the East China Sea, we collected samples and data from T. japonicus targeting fishing gears such as trawls, canvas spreader stow nets and longlines from 2016 to 2020. We estimated growth and mortality parameters using the FiSAT II software, and calculated the size limit standards for capture. The results showed that the inflection point of anal length, the critical anal length and the anal length of one-year-old T. japonicus was 382.84, 397.12, and 216.05 mm, respectively. The anal length of maturity was 230.38 mm, and the minimum capture size (anal length) was 219.23 mm. Based on the yield per recruitment analysis using Beverton-Holt model, the current fishery reference points were under overfishing condition (t_c=0.38 a, F=2.11), and the suggested optimum capture size was 364.64 mm. There would be a sharp decline of T. japonicus catches in the East China Sea if the suggested minimum capture size was substantially higher, which might be non-practical for local fishermen. Therefore, we suggested 220 mm as the capture size limit, which was close to the anal length of one-year-old fish and the anal length of maturity.