Dynamics of the sanry population in the pacific ocean off northern Japan. II. Estimation of the catchability coefficient q with the shift of fishing ground.
Dynamics of the sanry population in the pacific ocean off northern Japan. II. Estimation of the catchability coefficient q with the shift of fishing ground.
复制标题
日本北部太平洋海域的桑里种群动态。
DOI：
10.2331/suisan.42.943
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发表时间：
1976
期刊：
影响因子：
--
通讯作者：
Syoiti Tanaka
中科院分区：
文献类型：
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作者：
Y. Matsumiya;Syoiti Tanaka
将渔获量、迁移量、迁出量和滞留量的影响纳入不同大小类别和不同渔场的秋刀鱼种群数量丰富度指数，建立了一个简单的动态模型。在该模型中，迁入率或迁移率与捕捞系数Q成线性关系。假设鱼群只向西南方向移动，则可根据渔场的移动来估计可能的最小迁移率。Q的可能范围是从这些最小速率得到的。结果表明，Q=0.00028除1个外，满足所有24个条件，因此被用作Q的估计值。根据各种统计数据和Q的值，计算了各年龄段和大小类别的以下数量：总渔获量、总可利用种群数量、迁徙数量、开采率、10日有效捕捞强度指数平均值和10日停留周期平均值。研究了秋刀鱼种群动态的年变化。近年来渔获量减少似乎是由于捕捞强度降低，其次是人口丰度下降所致。捕捞强度的降低表明，种群数量下降的原因不是过度捕捞。
Incorporating the effect of catch, immigration, emigration and stay of fish shoals into the abundance index in number of the saury population by size category and fishing ground, a simple dynamics model was developed. From this model, a linear relation is obtained between the rate of immigration or emigration and the catchability coefficient q. Possible minimum rate is estimated from the shift of the fishing ground, assuming that the fish shoals move only in the south-west direction. Possible ranges of q are obtained from these minimum rates. It was found that q=0.00028 meets all 24 requirements except one, and hence was adopted as the estimate of q. From various statistics and the value of q, the following quantities were calculated for every year and size category: total catch in number, total available population in number, number of the immigrants, rate of exploitation, mean of effective overall fishing intensity index in a 10-day period and mean of the number of 10-day periods of stay. The yearly variation of the dynamics of the saury population was examined. The poor catch in recent years seems to be caused, firstly by the decrease of fishing intensity, and secondly, by the decline of the abundance of the population. Reduced fishing intensity suggests that the cause of the population decline is not due to overfishing.