浙北近海曼氏无针乌贼增殖放流效果评估

为修复浙北近海曼氏无针乌贼(Sepiella maindroni)资源,2013—2016年实施了大规模放流,累计增殖放流受精卵7835×104粒,同期还开展了跟踪监测调查。本研究利用放流前后的定点资料和补充采样数据,估算了生长参数和死亡系数等指标,并构建资源评估模型,模拟分析了渔获产量和残存率的变化趋势。结果表明,2013—2016年浙北海域放流曼氏无针乌贼极限体长为138 mm,年生长系数K为2.354,t0为–0.05237 a,年总死亡系数Z为2.83,年自然死亡系数M为1.74,年捕捞死亡系数F为1.09;现行捕捞强度下,每投放1×104粒受精卵,可形成137.3 kg产量,同时还补充了502 ind性成熟个体,增殖放流在一定程度上起到了种群修复和增产增收的目的。评估结果显示,将开捕时间推迟2个月,捕捞产量可增加10.0%,发育至性成熟个体增加27.5%;捕捞强度也是影响放流效果的重要因素之一,若将年捕捞死亡系数降至0.76,捕捞产量最高可达155.6 kg,发育至性成熟个体增加29.4%。最后,针对研究结果提出提高曼氏无针乌贼放流效果和合理利用资源的建议。

Effect and assessment of enhancement release of Sepiella maindroni in the northern coastal water of Zhejiang

In order to restore the Sepiella maindroni resources in northern coastal water of Zhejiang Province, the large-scale release had been carried out from 2013 to 2016. A total of 7835×10⁴ ind. fertilized eggs were released, and at the same time, the follow-up monitoring survey were carried out. Considering the certain point information and supplementary sample data, we estimated several indicators including growth equation and death coefficient, built the model of fishery stock assessment, finished the simulation analysis of the variation trend of fishery production and residual rate. Meanwhile, we introduced the supplementary abilities of breeding population to quantitatively evaluate the enhancement effect. The results indicate that, the released Sepiella Maindroni in northern area of Zhejiang Province between year 2013 to 2016, its limited body length is 138 mm, the growth parameters K is 2.354, t₀ is -0.05237 a., the total mortality coefficient (Z) is 3.04, the natural mortality coefficient (M) is 1.74, the fishing mortality coefficient (F) is 1.09. Under the current fishing intensity, releasing 1×10⁴ ind. fertilized eggs could receive 137.3 kg production, when still supplement 502 ind. sexually mature individuals into study area. Generally speaking, stock enhancement serves the purpose of population restoration and increases both production and income in certain degree. The model estimation analysis shows:if people could postpone the capture two month, the capture production may add 10.0%, and the growth of the sexually mature individuals will also increase 27.5%. On the other hand, if the fishing mortality coefficient could reduce to 0.76, the production may increase to 155.6 kg/a, and the proportion of sexually mature individuals may add 29.4%. Finally, we hope could put forward the suggestions about improving the effect of releasing Sepiella maindroni and using the resources reasonably according to the research.