期刊
ICES JOURNAL OF MARINE SCIENCE
卷 75, 期 2, 页码 610-620出版社
OXFORD UNIV PRESS
DOI: 10.1093/icesjms/fsx177
关键词
catchability coefficient; data limited; data-poor; fishing effort; mean length; natural mortality rate; Nephrops; non-equilibrium conditions
资金
- Virginia Sea Grant: Stock Assessment Analytical Methods (SAAM) [NA14OAR4170297]
- Malaysian Ministry of Higher Education-University of Malaya scholarship
Gedamke and Hoenig (2006) (Transactions of the American Fisheries Society, 135: 476-487) developed a non-equilibrium version of the Beverton and Holt estimator of total mortality rate, Z, based on mean length and thereby increased the usefulness of length-based methods. In this study, we extend their model by replacing period-specific Z parameters with the year-specific parameterization Z(y) = qf(y) + M where q is the catchability coefficient, f(y) is the fishing effort in year y, F (= qf) is the fishing mortality rate, and M is the natural mortality rate. Thus, the problem reduces to estimating just three parameters: q, M and residual variance. We used Monte Carlo simulation to study the model behaviour. Estimates of q and M are highly negatively correlated and may or may not be reliable; however, the estimates of corresponding Z's are more precise than estimates of F and are generally reliable, even when uncertainty about the mean lengths is high. This length-based method appears to work best for stocks with rapid growth rate. Contrast in effort data may not be necessary for reliable estimates of Z's. This approach forms a bridge between data-limited models and more complex models. We apply the method to the Norway lobster Nephrops norvegicus stock in Portugal as an example.
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