The effect of including length structure in yield-per-recruit estimates for northeast Arctic cod
<qd> Kvamme, C., and Bogstad, B. 2007. The effect of including length structure in yield-per-recruit estimates for northeast Arctic cod – ICES Journal of Marine Science, 64. </qd>For northeast Arctic cod ( Gadus morhua ), traditional age-based estimates of yield per recruit (YPR) are com...
Published in: | ICES Journal of Marine Science |
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Main Authors: | , |
Format: | Text |
Language: | English |
Published: |
Oxford University Press
2007
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Subjects: | |
Online Access: | http://icesjms.oxfordjournals.org/cgi/content/short/fsl027v1 https://doi.org/10.1093/icesjms/fsl027 |
Summary: | <qd> Kvamme, C., and Bogstad, B. 2007. The effect of including length structure in yield-per-recruit estimates for northeast Arctic cod – ICES Journal of Marine Science, 64. </qd>For northeast Arctic cod ( Gadus morhua ), traditional age-based estimates of yield per recruit (YPR) are compared with alternative, though comparable, YPR estimates calculated using an age–length-structured model. In the age–length-structured model, growth, fishing mortality, and natural mortality depend only on length, not on age. This model considers possible changes in size-at-age caused by, for example, a length-selective fishery, and therefore, by comparing the different YPR estimates, the importance of considering the stock's length structure can be evaluated. Length- and weight-at-age of stock and catches were influenced by exploitation pattern and pressure. Such changes are not considered in traditional estimates of YPR, for which weight-at-age is fixed and strictly speaking only representative for the current fishery. Consequently, traditional YPR estimates were somewhat higher than the age–length-based estimates for exploiting smaller fish than at present, and the other way round for exploiting larger fish. Both models indicated a gain in YPR for reducing just exploitation pressure (traditional YPR, 13%; alternative model, 20%) or both reducing exploitation pressure and postponing exploitation (traditional YPR, 23–31%; alternative model, 33–48%), compared with the current fishery. |
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