Assessing the precision of the estimated age distribution of the commercial catch of Northeast Arctic cod
Working paper
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http://hdl.handle.net/11250/100487Utgivelsesdato
2001Metadata
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Sammendrag
The assessment of Northeast Arctic cod is based on estimates of the commercial catch
numbers at age. The age structure of the catch is estimated by sampling individuals from
commercial fishing trips. Though it is commonly assumed that the 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 have more similar ages than those in the total catch. For
Northeast Arctic cod, the intra-cluster correlation for age is positive and thus the effective
sample size is much smaller than the number of fish aged. It is shown, given the number
of fish aged, that the precision of the estimated age distribution is rather low, and that the
number of fish aged from each trip could be reduced from approximately 80 to 20
without a significant loss in precision.
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ICES CM documents2001/P:01