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Changes in natural mortality of Atlantic cod (Gadus morhua) on Eastern Georges Bank

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Abstract

The assessment of Eastern Georges Bank cod with the assumption of a constant natural mortality of 0.2 has over-estimated stock productivity, resulting in a severe retrospective pattern since the late 2000s. Comparing relative exploitation rate (ratio of fishery catch at age to survey abundance indices at age) with total mortality calculated from the age distribution in surveys indicated a conflict when constant natural mortality was assumed. This inconsistency implies an increase in natural mortality since the mid-1990s. In this paper, natural mortality estimated by Virtual Population Analysis (VPA) indicated that natural mortality for this stock has increased to 0.8 since the mid-1990s for ages 6+. Potential factors contributing to this elevated natural mortality, including poor fish conditions and increased losses due to seal predation were discussed.

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  1. Fisheries and Oceans Canada, St. Andrews Biological Station, St. Andrews, New Brunswick, E5B 2L9, Canada

    Yanjun Wang

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  1. Yanjun Wang
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Correspondence to Yanjun Wang.

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Wang, Y. Changes in natural mortality of Atlantic cod (Gadus morhua) on Eastern Georges Bank. J. Ocean Univ. China 15, 879–889 (2016). https://doi.org/10.1007/s11802-016-3019-4

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  • DOI: https://doi.org/10.1007/s11802-016-3019-4

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