Affiliation:
1. Institute of Marine Research PO Box 1870 Nordnes, N-5817 Bergen, Norway
Abstract
Abstract
Assessment of Northeast Arctic cod is based on estimates of the commercial catch in numbers at age. The age structure of the catch is estimated by sampling fish from commercial fishing trips. Although it is commonly assumed that a sample of individuals is a random sample from the population, fish sampled from the same trip (i.e. from a “cluster” of fish) tend to be more similar in age than those in the total catch. For Northeast Arctic cod, the intracluster correlation for age is positive, and therefore the effective sample size is much smaller than the number of fish aged. Given the number of fish aged, the precision of the estimated age distribution is rather low, and the number of fish aged from each trip could be reduced from approximately 85 to 20 without a significant loss in precision.
Publisher
Oxford University Press (OUP)
Subject
Ecology,Aquatic Science,Ecology, Evolution, Behavior and Systematics,Oceanography
Reference14 articles.
1. Time series analysis of catch at age observations;Gudmundsson;Applied Statistics – Journal of the Royal Statistical Society, Series C,1994
2. Use of a log-linear model with the EM algorithm to correct estimates of stock composition and to convert length to age;Hoenig;Transactions of the American Fisheries Society,1987
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