采样设计对估计矛尾虾虎鱼体长-体质量关系参数b的影响

鱼类体长-体重关系参数估计的准确与否影响进一步的渔业资源评估和管理。不同采样设计获得的生物学数据,对鱼类体长-体重关系参数b估计可能会有一定的影响。本文基于2013-2014年在黄河口水域调查获得的矛尾虾虎鱼(Chaemrichthys stigmatias)体长、体重数据,采用计算机模拟重抽样方法,选取相对估计误差和相对偏差两个指标,比较了不同采样设计对估计矛尾虾虎鱼体长-体重关系参数b的影响。结果表明,增加样本量可有效提高其体长-体重关系参数b的估计精度。不同季节数据对参数估计精度具有不同影响,应用多季节调查采样数据估计参数精度往往优于单季节采样。夏季数据对矛尾虾虎鱼体长-体重关系参数估计尤为重要。方案9(夏-冬季方案)在样本量达到540尾时,相对估计误差REE为2.08%,相对偏差RB的绝对值为0.71%,在相同样本量下该设计方案表现最好。在估计黄河口矛尾虾虎鱼等鱼类体长-体重关系参数时,应保证获得一定样本量的对参数估计具有较大影响的季节的生物学数据。

Effect of sampling design on the estimation of length-weight relationship parameter b of Chaemrichthys stigmatias

The length-weight relationship of fish stock is one of the commonly used formulas in fishery ecology study. The length-weight relationship is significant for the assessment of fishery resources. It is often used to estimate the average weight of a given length and estimate the status of the fish stock. The accuracy of the estimates of length-weight relationship parameters for fish stock affects the stock assessment and management. One way to increase the estimates of length-weight relationship parameters is to conduct sampling as frequently as possible. However, surveying in a marine ecosystem tends to be expensive and difficult, and frequent samplings may also increase unnecessary sampling mortality of fish species. Based on the biological data on the length and weight of Chaemrichthys stigmatias obtained from fishery-independent surveys conducted in June, July, August, October 2013 and February, April, and May 2014 in the Yellow River Estuary, the influence of sampling designs on the estimation of parameter b of the length-weight relationship of Chaemrichthys stigmatias was examined using computer simulation study. The results showed that the estimation accuracy of length-weight relationship parameter improved with the sample size increasing. The length and weight data in different seasons showed different impact on the estimation accuracy of the parameter, and the data in summer was particularly important in improving the accuracy and precision of estimation of body length-weight relationship parameter b for Chaemrichthys stigmatias. The precision and accuracy of parameter estimate based on the data from more seasons were usually higher than those using data in single season. Scheme 9 (sampling in summer and winter) performed the best at the same sample size among all the fifteen sampling design schemes. The relative estimation error of parameter b of length-weight relationship was 2.08%, and the absolute value of the relative bias was 0.71% for scheme 9 at the sample size of 540 individuals. Under the circumstance that there is no guarantee for fishery-independent surveys in each season, only sampling in the summer and winter seasons can provide a more accurate estimation of the length-weight relationship parameter b of Chaemrichthys stigmatias. Due to the different life history characteristics of different fish species, the estimation of the length-weight relationship parameters should be analyzed specifically. Enough biological data from representative seasons that has great effect on the estimation of parameter should be obtained when we estimate the length-weight relationship for fish population like Chaemrichthys stigmatias in the Yellow River estuary. In this paper, using Chaemrichthys stigmatias as an example, the influence of sampling design on the estimation of length-weight relationship parameter was explored, which would provide a reference for the estimation of length-weight relationship parameter of other fish stocks.