Argued that, where the nature of the relationship between population size and recruitment is unknown, a precautionary approach would be to aim to maintain populations above 40% of their unexploited size.
Used a bioeconomic model to examine effects of different reserve areas on economic yields from the Barents Sea cod fishery. Reserves reduced economic yield from the fishery but increased cod population size. The system was also modeled with an ecological shock - a ten year period of recruitment failure. Reserves supported populations through this recruitment failure and were found to be bioeconomically beneficial when there were moderate levels of movement of cod from reserves to fishing grounds (40 to 60% of cod leave reserve in a year). This allowed reserve benefits to be captured by the fishery. The largest reserves modeled, covering 70% of the management area, offered the greatest future security for stocks, but had the highest cost in terms of current yields. How large reserves should be depends on the degree to which populations are subject to external shocks, and the degree of risk managers are willing to accept. In general, reserves covering 30 to 50% of the area provided significant protection for stocks without greatly reducing current economic benefits.
Man et al., 1995:
Modeled the persistence of an exploited metapopulation distributed across a series of habitat patches. Reserves (protected patches) became highly beneficial to population persistence as the local extinction rate in patches increased (due to increasing fishing intensities). This is because reserves provided a source of offspring to replenish fished out patches. Reserves became beneficial as exploitation rates increased, reaching a maximum of 50% of the patches protected at the highest levels of fishing. However, over a wide range of fishing intensities, optimal reserve fractions ranged between 20 and 40%.
Soh et al., 1998:
Modeled the effects of closing hotspot areas for catches of two species of rockfish in the Gulf of Alaska. The fishery for these species is unselective and currently there are high levels of discards of over-quota fish, ranging from 15 to over 60% of catches. Three areas of reserves were simulated, covering approximately 4, 9 and 16% of the trawlable shelf area of the region. Because reserves