Effects of fish density distribution and effort distribution on catchability

Ellis, Nick & Wang, You-Gan (2007) Effects of fish density distribution and effort distribution on catchability. ICES Journal of Marine Science, 64(1), pp. 178-191.

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The effects of fish density distribution and effort distribution on the overall catchability coefficient are examined. Emphasis is also on how aggregation and effort distribution interact to affect overall catch rate [catch per unit effort (cpue)]. In particular, it is proposed to evaluate three indices, the catchability index, the knowledge parameter, and the aggregation index, to describe the effectiveness of targeting and the effects on overall catchability in the stock area. Analytical expressions are provided so that these indices can easily be calculated. The average of the cpue calculated from small units where fishing is random is a better index for measuring the stock abundance. The overall cpue, the ratio of lumped catch and effort, together with the average cpue, can be used to assess the effectiveness of targeting. The proposed methods are applied to the commercial catch and effort data from the Australian northern prawn fishery. The indices are obtained assuming a power law for the effort distribution as an approximation of targeting during the fishing operation. Targeting increased catchability in some areas by 10%, which may have important implications on management advice.

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23 citations in Web of Science®

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ID Code: 90518
Item Type: Journal Article
Refereed: Yes
Keywords: aggregation, catchability, catch and effort data, density distribution, effort distribution, stock assessment, northern-prawn-fishery, dependent catchability, spatial-distribution, catch equations, technology, abundance, models, impact, cpue
DOI: 10.1093/icesjms/fsl015
ISSN: 1054-3139
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Deposited On: 18 Nov 2015 01:40
Last Modified: 24 Nov 2015 02:04

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