鱼类自然死亡系数评估研究进展

自然死亡系数是渔业资源评估中不可或缺的重要参数,其准确度直接决定了资源评估结果的可靠性,进而影响渔业管理策略的制定。本文从生活史参数、标志回捕和年龄结构3个方面列举了国内外自然死亡系数的常用评估方法,讨论了相关方法的优缺点及影响因素,并以犬齿牙鲆(Paralichthys dentatus)和中国近海鱼类为例对比分析不同模型的计算结果。在此基础上,着重介绍了Pauly经验公式在中国近海主要经济鱼类自然死亡系数评估中的应用进展及存在问题。根据渔业资源调查和研究数据现状,认为现阶段使用Pauly经验公式评估中国近海经济鱼类自然死亡系数具有积极作用。

Assessment of natural mortality coefficients in fish stocks: a review

Natural mortality coefficient (M) is a key parameter in fisheries stock assessment. Its accuracy directly determines the reliability of assessment results and also influences the establishment of fisheries management. Most mathematical models of fish stock dynamics incorporate M, either directly or indirectly. Fishery scientists have explored accurate estimates of M for a long time, in order to develop a more precise understanding of fish populations and to establish a more scientific basis for managing fisheries resources and sustainable development. The present study introduces and evaluates the most common models for estimating natural mortality coefficients for fish populations from three aspects, namely life-history parameters, tag-return, and age-structure. The first approach to estimate the instantaneous rate of natural mortality in fish stocks is based on the observation that M is strongly correlated with life history parameters, such as maximum observed age, age at reproductive maturity, asymptotic fish length, and growth rate. The Pauly empirical equation, Gislason empirical equation, and Tanaka''s maximum observed age''s method are among the most commonly used methods for assessing inshore fisheries in China. By classifying tagging data, based on catch per unit effort, size at release, and the probability of tag loss, Chapman, Hampton, and Treble have each constructed their own models, and some scholars have combined these methods to develop a model that is superior to any of the individual models. The assessment results of using tag-return methods would have a high reliability, but the huge costs of investigation, lower credibility of recapture, and prior model assumptions contribute to poor generality. Considering that age is the potentially most important factor affecting estimates of M, virtual population analysis (VPA) and cohort analysis (CA) are established using catch-at-age data. These methods could be used to reliably estimate fish stocks with long-term catch data. However, considering the incomplete and inaccurate statues of historical catch data in Chinese coastal fishes, the practicality of the VPA or CA models is relatively low. Meanwhile, taking Paralichthys dentatus and some coastal fish stocks as examples, this study compared estimation results through different methods and found that Pauly empirical equation is more reasonable to calculate M. Then, this paper introduced the misapplications of Pauly empirical equation in inshore fisheries of China. The main misapplications were equation error, unit error and calculation mistake. According to the limited data and fishery exploitation status, we suggest that Pauly empirical equation has a positive meaning to assess the M for major economic fish stocks in China.