剩余产量模型形状参数对印度洋黄鳍金枪鱼资源评估的影响

剩余产量模型中的Schaefer模型与Fox模型在渔业资源评估中被广泛应用,但这两个模型是剩余产量模型一般形式Pella-Tomlinson模型的两个特例,分别由形状参数的两个不同值确定。由于形状参数直接影响种群的生产能力,并与种群的年龄结构、繁殖能力等紧密相关,将形状参数固定为某个值,可能会影响剩余产量模型评估结果的可靠性,为此,本文利用印度洋黄鳍金枪鱼(Thunnus albacares)数据,分析剩余产量模型形状参数对渔业资源评估的影响。结果表明:(1)形状参数较难估计,并随数据时段的不同,形状参数的最佳取值范围会有很大的不同;(2)形状参数会对承载能力、内禀增长率的估计产生显著影响;(3)随形状参数值的增加,资源被掏空率与过度捕捞程度会不断增加,因此,不同形状参数的设置会对渔业资源状态及过度捕捞程度的判断产生重要影响。

Impacts of shape parameter of surplus production model on stock assessment of Indian Ocean yellowfin tuna

Schaefer form and Fox form of surplus production model are widely used in fishery stock assessment. However, the two models are two special cases of the generalized surplus production model, i.e. Pella-Tomlinson model, with two special values of the shape parameter. Because the shape parameter has a close relationship with the age structure and reproductive capacity of the population and directly affects the modeled population productivity, fixing the shape parameter at some special values would raise doubts about the results of the stock assessment models of the model. The impacts of shape parameter on stock assessment results were analyzed based on Indian Ocean yellowfin tuna (Thunnus albacares) data. The results showed:1) the shape parameter was difficult to be estimated and its best value range would be greatly different with different data sets from different time periods; 2) the shape parameter had obvious impacts on the estimate of carrying capacity and the intrinsic rate of population increase; 3) the depletion levels of the stock and the overfished or overfishing levels were enhanced with the value of the shape parameter increasing and accordingly the shape parameter had important impacts on the inference of stock status and overfished and/or overfishing levels.