Precision estimates and suggested sample sizes for length-frequency data

Gerritsen, Hans D. and McGrath, David (2007) Precision estimates and suggested sample sizes for length-frequency data. Fishery Bulletin, 105(1), pp. 116-120.

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For most fisheries applications, the shape of a length-frequency distribution is much more important than its mean length or variance. This makes it difficult to evaluate at which point a sample size is adequate. By estimating the coefficient of variation of the counts in each length class and taking a weighted mean of these, a measure of precision was obtained that takes the precision in all length classes into account. The precision estimates were closely associated with the ratio of the sample size to the number of size classes in each sample. As a rule-of-thumb, a minimum sample size of 10 times the number of length classes in the sample is suggested because the precision deteriorates rapidly for smaller sample sizes. In absence of such a rule-of-thumb, samplers have previously under-estimated the required sample size for samples with large fish, while over-sampling small fish of the same species.

Item Type: Article
Title: Precision estimates and suggested sample sizes for length-frequency data
Personal Creator/Author:
Gerritsen, Hans D.
McGrath, David
Refereed: Yes
Journal or Publication Title: Fishery Bulletin
Volume: 105
Number: 1
Page Range: pp. 116-120
Date: 2007
ISSN: 0090-0656
Issuing Agency: United States National Marine Fisheries Service
Subjects: Biology
Item ID: 8936
Depositing User: Patti M. Marraro
Date Deposited: 27 Jun 2012 16:56
Last Modified: 27 Jun 2012 16:56

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