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When reproductive value exceeds economic value: an example from the Newfoundland cod fishery

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Cailin Xu, Ocean Sciences Center, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada A1B 3X7
Tel.: (709) 725 5663
E-mail: cailinx@mun.ca

Abstract

The Northern Cod (Gadus morhua) fishery supported the removal of approximately 200 000 tonnes per year for centuries until collapse in the late 1980s and closure in 1992. Long recovery times, on the order of a decade or more, are now known to be regular concomitant of steep population declines in fish populations. We investigated reproductive value as an alternative to economic value in assessing fisheries sustainability. Our analysis showed that in cod, price-driven heavy fishing (i.e. fishing mortality positively related to body mass and its dollar value) dramatically impaired reproductive capacity by sacrificing future egg production of large fish. Management based upon current value (either in terms of biomass or equivalently dollar value) substantially underestimates the value of large individuals to the stock; this drove the Northern Cod stock towards collapse by failing to protect individuals with high future value. Our results provide a general explanation for the erosion, collapse and prolonged recovery of a long-lived species where reproductive value increases rapidly with increasing size. Failure to compute and communicate future value relative to current dollar value to resource harvesters leads to unrealistic perceptions of sustainable resource use.

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