基于Beverton－Holt模型的东海带鱼资源利用与管理

根据1959-2003年收集的东海带鱼年龄组成、肛长等生物学资料,对东海带鱼群体的利用结构进行了分析,并利用Beverton-Holt模型的单位补充量渔获量理论,分析和探讨了东海带鱼资源的合理利用.结果表明:1)东海带鱼渔获群体组成低龄化趋势明显,渔获年龄由20世纪50年代末期的0～6龄缩小为21世纪初的0～4龄,主要组成群体为0龄和1龄鱼,2龄鱼的比例由50年代末期的12.84%下降到21世纪初的6.91%,3龄鱼的下降幅度更大,由原来的4.92%下降为0.57%,渔获年龄组成进一步简单化.2)2000-2003年东海带鱼的年平均开发率E为0.864,远超过现行渔业下的最适开发率0.51,东海带鱼资源处于过度捕捞状态.3)增加东海带鱼单位补充量渔获量(YM/R)最有效的方法是提高其开捕年龄,若将带鱼开捕年龄tc由目前的0.5龄提高到1龄,其单位补充量渔获量可比2003年增加55.38%;若tc提高到1.5龄,其单位补充量渔获量可增加100.81%;若tc提高到2龄,其单位渔获量可增加130.52%;如果提高到2.75龄,其单位补充量渔获量将出现最大值,可增加145.23%左右.在当前大幅降低捕捞强度有较大困难的情况下,建议采取逐年、逐步提高带鱼开捕规格并适当降低其捕捞强度,以更好地恢复东海带鱼资源.

Utilization and management of Trichiurus japonicus resources in East China Sea based on Beverton-Holt model

In this paper, the population structure of Trichiurus japonicus in East China Sea was analyzed based on the data of its age composition and anus length in 2002-2004, and the rational utilization of T. japonicus resources in the Sea was approached by using the catch (in mass) per recruit theory of Beverton-Holt model. The results revealed that: (1) there was a miniaturization trend of the T. japonicus population in East China Sea. The range of age composition changed from 0-6 year in the late 1950's to 0-4 year in the early 21st century, and the population was dominated by the group of 0-1 year now. The percentage of 2-year old T. japonicus decreased from 12.84% in the late 1950s' to 6.91% in the early 21st century, and that of 3-year old T. japonicus decreased from 4.92% in the late 1950s' to 0.57% in the early 21st century; (2) the exploitation rate of T. japonicus in the period of 2000-2003 was 0.864, which was beyond of the optimum exploitation rate of 0.51, suggesting that the T. japonicus in East China Sea was under over-fishing; and (3) to enhance the age value at first capture (t(c)) was the best measure of increasing the catch (in mass) per recruit of T. japonicus. The age at recruitment (t(r)) and the t(c) of T. japonicus in East China Sea was 0. 25 and 0.5 at present, respectively. If the t(c) changed from 0.5 to 1, the unit catch would be increased by 55.38%, and if the t(c) changed to 1.5, 2 or 2.75, it would be increased by 100.81%, 130.52% or 145.23%, respectively. It was suggested that due to the difficulties in greatly reducing catching intensity, it could be available to properly increase the to value while decrease the catching intensity to protect the T. japonicus resources in East China Sea and realize their sustainable use.