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Marine Ecology Progress Series

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MEPS 240:225-233 (2002)  -  doi:10.3354/meps240225

Risk of collapse in the eastern Baltic cod fishery

Niclas Jonzén1,2,*, Massimiliano Cardinale3, Anna Gårdmark2, Fredrik Arrhenius3, Per Lundberg2

1Department of Biology and Environmental Sciences, University of Jyväskylä, PO Box 35, 40351, Jyväskylä, Finland
2Department of Theoretical Ecology, Ecology Building, Lund University, 22362 Lund, Sweden
3National Board of Fisheries, Institute of Marine Research, PO Box 4, 45321 Lysekil, Sweden
*Correspondence address: Department of Theoretical Ecology, Ecology Building, Lund University, 22362 Lund, Sweden. E mail:

ABSTRACT: The eastern Baltic cod fishery, as many fisheries worldwide, is experiencing a major crisis. The combination of current environmental conditions, fishing mortality rates, and stock size indicates that this fishery is not sustainable. In order to rebuild the population and sustain the fishery in the future, it is essential to define a biologically appropriate exploitation level. In this paper, we take a decision-theoretical approach and use risk analysis to compare different management actions in terms of fishing mortality rates, and predict stock size in a short, medium and long-term perspective. We consider alternative hypotheses about the stock biomass in 1999 and analyse the risk of stock decline below three thresholds: quasi-extinction (Bext, defined by us), the safe biological limit, and the precautionary approach limit as defined by the International Council for the Exploration of the Sea (ICES). Results show that the current fishing mortality implies a tremendous risk of driving the Baltic cod stock below Bext (1000 t) within 10 yr. This result is robust to alternative assumptions about model structure as well as to the magnitude of environmental stochasticity. Hence, we consider a substantial reduction of the fishing mortality to be the only way of avoiding the far-reaching ecological and socio-economic consequences of continued exploitation at current levels.

KEY WORDS: Risk analysis · Stochastic population dynamics · Time series analysis · Gadus morhua · Baltic Sea

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