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The influence of life historyattributes and fishing pressure on the efficacy of marine reserves.

Leah R. Gerber, Peter M. Kareiva,and Jordi Bascompte, 2002.
Biological Conservation, 106: 11-18.

ABSTRACT: Two key questionsregarding "no-take" marine reserves are: (i) how effective are reserveslikely to be, and (ii) how does effectiveness vary with life history attributesand the relative size of reserves. To investigate these questions, we usea simple Ricker model that includes fishing, larval dispersal, and larvalloss while in a planktonic pool, and that tracks protected and unprotectedpopulations. We applied two different measures of reserve effectivenessto our simulation results. One metric was intended to reflect goals orientedtowards conservation and the second was intended to reflect fishery enhancementgoals. Both metrics compare the situation before reserves are establishedto after the reserves have been in place and a new equilibrium was reached.Yield effectiveness is defined as the total equilibrium annual harvestafter reserves are established divided by the total annual harvest beforereserves are established. Conservation effectiveness is defined as theaverage adult density inside the reserve divided by the average densityin the same area prior to reserve establishment. A substantial fractionof the 5120 simulated parameter combinations representing different harvestrates and life history attributes went extinct in the absence of a reserve,and these scenarios leading to extinction could be predicted accurately(85% aptly classified) simply on the basis of exploitation rate and populationgrowth rate. Of the cases that did not go extinct, we compared the performanceof reserves as measured by each effectiveness metric. Few of the cases(less than 8%) produced effective reserves as measured in terms of increasedharvest; whereas over half of the cases resulted in effective reservesas measured by conservation effectiveness. Moreover, the two measures ofreserve effectiveness were only weakly correlated. Simple linear regressionor polynomial regression could explain at most 23% of the variation inreserve effectiveness as measured by either metric. As expected, the sizeof the reserve area had a marked and typically negative effect on totalannual yield, which suggests that while marine protected areas may do agood job of conserving protected populations, there will generally be pressurefrom the fishery industry to keep them small because of their tendecy toreduce total catch.

The influence of life historyattributes and fishing pressure on the efficacy of marine reserves.

Leah R. Gerber, Peter M. Kareiva,and Jordi Bascompte, 2002. Biological Conservation, 106: 11-18.

Leah R. Gerber, Peter M. Kareiva,and Jordi Bascompte, 2002.
Biological Conservation, 106: 11-18.