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ICES Journal of Marine Science: Journal du Conseil 2005 62(1):65-74; doi:10.1016/j.icesjms.2004.10.003
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© 2004 International Council for the Exploration of the Sea

Effect of changes in reproductive potential on perceived productivity of three Northwest Atlantic cod (Gadus morhua) stocks

M. Joanne Morgan* and John Brattey

Department of Fisheries and Oceans PO Box 5667, St. John's, Newfoundland A1C 5X1, Canada

*Correspondence to M. J. Morgan: tel: +1 709 772 2261; fax: +1 709 772 4105. e-mail: morganj{at}dfo-mpo.gc.ca.

Variation in maturity-at-age, sex ratio, and potential egg production (through changes in length at age) were examined for northern cod (NAFO Division 2J + 3KL), southern Grand Bank cod (3NO), and southern Newfoundland cod (3Ps). All showed significant interannual variability in each stock. Estimates of reproductive potential were produced by sequentially incorporating estimates of proportion mature at age, sex ratio at age, and potential egg production. The estimates of reproductive potential produced by each method were broadly similar, but there were important differences. This leads to differing perceptions of stock productivity, as measured by relative rate of recruitment of a stock and in the spawning stock produced per recruit. These differing perceptions can have a major impact on expectations for the recovery of depleted stocks and the sustainability of various levels of fishing. Efforts should be made to improve estimates of reproductive potential by further exploring the impacts of changes in the spawning characteristics of populations, and by collecting such basic information as fecundity data.

Keywords: fecundity, Gadus morhua, maturity, reproductive potential, sex ratio, stock recruit

Received 11 May 2004; accepted 9 October 2004.


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