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

C. Roeckmann, U.A. Schneider, M.A. St. John, R.S.J. Tol

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

A spatially disaggregated, discrete time, age-structured model for the Eastern Baltic cod (Gadus morhua callarias L.) stock was constructed, in order to test the implications of the establishment of a marine reserve in the Baltic Sea. 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 subdivision (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. Crown Copyright © 2006.
Original languageEnglish
Pages (from-to)1-13
Number of pages13
JournalFisheries Research
Volume85
DOIs
Publication statusPublished - 2007

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marine park
cod (fish)
population dynamics
environmental conditions
environmental factors
fishing mortality
fishing
gadoid fishery
testing
fisheries
Gadus morhua
Baltic Sea
age structure
multiple regression
extinction
predation
fishery
mortality
simulation
sea

Cite this

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title = "Testing the implications of a permanent or seasonal marine reserve on the population dynamics of eastern baltic cod under varying environmental conditions",
abstract = "A spatially disaggregated, discrete time, age-structured model for the Eastern Baltic cod (Gadus morhua callarias L.) stock was constructed, in order to test the implications of the establishment of a marine reserve in the Baltic Sea. 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 subdivision (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. Crown Copyright {\circledC} 2006.",
author = "C. Roeckmann and U.A. Schneider and {St. John}, M.A. and R.S.J. Tol",
year = "2007",
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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. / Roeckmann, C.; Schneider, U.A.; St. John, M.A.; Tol, R.S.J.

In: Fisheries Research, Vol. 85, 2007, p. 1-13.

Research output: Contribution to JournalArticleAcademicpeer-review

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AU - Tol, R.S.J.

PY - 2007

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AB - A spatially disaggregated, discrete time, age-structured model for the Eastern Baltic cod (Gadus morhua callarias L.) stock was constructed, in order to test the implications of the establishment of a marine reserve in the Baltic Sea. 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 subdivision (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. Crown Copyright © 2006.

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