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Testing the implications of a permanent or seasonal marine reserve on the population dynamics of Eastern Baltic cod under varying environmental conditions

Author

Listed:
  • Christine Roeckmann
  • Michael A. St.John
  • Uwe A. Schneider
  • Friedrich W. Koester
  • Richard S.J. Tol

    () (Economic and Social Research Institute, Dublin)

Abstract

In order to test the implications of the establishment of a marine reserve in the Baltic Sea, a spatially disaggregated, discrete time, age-structured model for the Eastern Baltic cod (Gadus morhua callarias L.) stock was constructed. Functional relationships for recruitment and predation mortality were developed by multiple regression analyses. The resultant model output compares well with observed data from the fishery. The model was then applied to simulate stock development over a 50 year time period using different management policies and a variety of environmental conditions. The investigated management policies reduce fishing mortality and range from a moratorium on the Eastern Baltic cod fishery via the establishment of a permanent or a seasonal marine reserve in ICES subdivision 25 to a fishing as usual scenario. The environmental conditions incorporated were based on the size of the reproductive volume (RV) and comprise a best case and a worst case of reproductive conditions, and two more realistic scenarios, where we assumed that a historic series of RV-sizes reoccurs over the simulation period. Our results show a strong dependence of stock dynamics on the environmental conditions. Under prevailing low RV, our model projects stock extinction by the year 2020, if fishing continues as usual. Under the restrictive scenarios, where fishing mortality is reduced either directly or by implementation of a marine reserve, the stock benefits from an increase in stock size and an improved age-structure. A seasonal closure of SD 25 as opposed to a closure of the entire Baltic Sea appears to be sufficient to prevent the Eastern Baltic cod stock from falling below safe biological limits.

Suggested Citation

  • Christine Roeckmann & Michael A. St.John & Uwe A. Schneider & Friedrich W. Koester & Richard S.J. Tol, 2005. "Testing the implications of a permanent or seasonal marine reserve on the population dynamics of Eastern Baltic cod under varying environmental conditions," Working Papers FNU-63, Research unit Sustainability and Global Change, Hamburg University, revised Jan 2006.
  • Handle: RePEc:sgc:wpaper:63
    as

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    File URL: http://www.fnu.zmaw.de/fileadmin/fnu-files/publication/working-papers/WP_FNU63_revised_Roeckmann.pdf
    File Function: First version, 2005
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    More about this item

    Keywords

    Baltic cod; management; age-structured model; population dynamics; MPA; environmental variability; reproductive volume;

    JEL classification:

    • Q22 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Renewable Resources and Conservation - - - Fishery

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