Order-restricted Bayesian estimation of the age composition of a population of Atlantic cod

• 成果类型: Article
• 署名作者: Nandram, B; Sedransk, J; Smith, SJ
• 署名单位: University System of Ohio; Case Western Reserve University; Fisheries & Oceans Canada; Bedford Institute of Oceanography
• 刊物名称: JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION
• ISSN/ISSBN: 0162-1459
• DOI: 10.2307/2291447
• 发表日期: 1997
• 页码: 33-40

摘要

The management of a commercial fishery often requires estimates of the age composition. These estimates are typically based on age and length data obtained from sampling the commercial landings from the fishery and the catches from a research vessel survey. We use data from annual research cruises of Georges Bank conducted by the Canadian Department of Fisheries and Oceans to show how inferences for Atlantic cod (Gadus morhua) can be improved. Traditionally, two-phase stratified sampling is used with fish length (or weight) as the stratification variable. Letting P-i. denote the proportion of fish belonging to length stratum i, and pi(ij) denote the proportion of fish belonging to age class j in stratum i, we use Bayesian methods to estimate P.(j) = Sigma(i) P-i.pi(ij), the proportion of fish that are age j. Specifications of smoothness, expressed as unimodal order relations among the pi(ij) (within and between the length strata), are incorporated into the prior distributions. Uncertainty about both the locations of the modes and the unimodality itself are included as part of the probabilistic specification. With computations facilitated by using the Gibbs sampler, we show that the smoothness conditions provide very large gains in precision. For the data analyzed in this article, one can obtain similar precision by using (a) a conventional analysis or (b)an analysis with order restrictions and a sample of half the size in (a). We also show that better estimates of the age composition provide improved estimates of the quantities used by fisheries managers to forecast the catches from cohorts of fish.