Marine Protected Areas Tools for Sustaining Ocean Ecosystems (2001) / Chapter Skim
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Appendix G: Description of Studies Estimating Marine Reserve Area Requirements
Appendix G: Description of Studies Estimating Marine Reserve Area Requirements
Pages 247-256
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From page 247... ...
OBJECTIVE: RISK MINIMIZATION Lauck et al., 1998: Examined the combined effects of variation in stock productivity, and errors in estimating mortality and population size, on the probability of managers successfully maintaining populations above target levels. In a simple model showed that, in the face of uncertainty in fishing mortality, reserves covering between 31 and 70% of fishing grounds would be needed to maintain populations above 60% of their unexploited size (argued to be an economic optimum)
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From page 248... ...
Roughgarden, 1998: Recommended maintaining exploited populations at 75% of their unexploited size in order to avoid recruitment overfishing. Gue'nette et al., 2000: Used a spatially explicit model to examine whether reserves could have prevented the collapse in 1992 of the migratory northern cod (Gadus morhua)
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From page 249... ...
Reserves (protected patches) became highly beneficial to population persistence as the local extinction rate in patches increased (due to increasing fishing intensities)
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From page 250... ...
The maximum long-term catch was from a reserve area of 25% and a moderately heavy level of fishing outside. The highest catch levels can be maintained using a range of reserve sizes provided fishing effort outside can be adjusted to appropriate levels.
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From page 251... ...
As fishing intensity increases, larger and larger reserves are required to sustain catches. In the most intensively exploited areas of the Caribbean, reserves covering 75-80% would be needed to maximize catches.
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From page 252... ...
in order to produce catches and spawning stock levels equivalent to those of an optimally controlled fishery (one where stock size is held at 60% of the unexploited level)
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From page 253... ...
Nevertheless, increases in spawning stock biomass reduce risk of overexploitation, and reserves ranging from 20 to 50% of the management area would offer significant levels of insurance against overfishing, although at increasing cost to present catches. Like Polacheck (1990)
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From page 254... ...
The results suggested a combined management strategy would be successful for the three species, with one third of the area protected distributed into reserves between 7 and 22km long across the coast of South Africa. Quinn et al., 1993: Used a population model to explore the role of reserves in managing the fishery for the red sea urchin (Stronglyocentrotus franciscanus)
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From page 255... ...
A 10% reserve decreased directional selection by 60%, while a 20% reserve would eliminate the selective effects of fishing from the population entirely. OBJECTIVE: INCREASE CONNECTIVITY AMONG RESERVES Roberts, in review a: Used a simple model in which reserve size and the fraction of the management area covered by reserves were varied to explore connectivity among reserves.
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From page 256... ...
He also examined connectivity as the 'target size' of reserves for dispersing propagules, expressed as the number of degrees of horizon covered by reserves. Target size increased steeply as the proportion of the management area protected grows, and was four times greater at 30% of the area in reserves compared to 5%.
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