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Fishery Bulletin 91(3). 1993 



of ages at sexual maturity and first capture, versus 

 those of refuge size and transfer rates. I suggest that 

 the former can have large influences for relatively 

 short-lived, fast-growing species like the surgeonfish 

 for which changes in age at first capture of only ±1 

 year represent a large fraction of its life span. 



Circumstantial evidence suggests that the relative 

 ages at sexual maturity and first capture can be im- 

 portant. Prior evaluations of the potential for MFRs to 

 conserve the SSB of overfished commercial stocks (e.g., 

 red snapper, Lutjanus campechanus) have concurrently 

 considered other management safeguards, such as size 

 limits in the non-closed area (Plan Development Team, 

 1990). However, nearshore reef fishes subject to recre- 

 ational harvest are often fished at sizes and ages con- 

 siderably less than those at sexual maturity, even on 

 moderately populated islands (e.g., the island of Ha- 



waii; Hayes et al., 1982). For reef fishes near densely 

 populated areas where exploitation is likely to be 

 intense on pre-reproductive fish, the potential for 

 MFRs to enhance SSB/R may be severely compro- 

 mised, even at closure sizes that are as large as is 

 practical (e.g., 25%). 



Compensatory emigration 



Density-dependent increases in the fundamental 

 transfer rate can in essence depress potential gains 

 in SSB/R in a manner analogous to that of a higher 

 but constant fundamental transfer rate. The obser- 

 vation that gains in SSB/R at increasingly large 

 refuge sizes were strongly offset by compensatory 

 movements in the jack, but not in the surgeonfish, 

 perhaps reflects the jack's slower growth rate, 

 greater longevity, and lower mortality rate. Longev- 

 ity, per se, may be important, because the model 

 that was used to describe compensatory emigration 

 is dependent upon time as well as age. 



SLOSS effects on MFR function 



Simberloff (1988) reviewed the SLOSS concept and 

 the meager results to date regarding whether mul- 

 tiple, small reserves function the same as single 

 reserves of equal total size. Historically the issue of 

 SLOSS has been applied to the preservation of 

 threatened and endangered species or the conserva- 

 tion of biotic diversity (Bell and Boecklen, 1990, 

 but see Goeden, 1979). It is increasingly apparent 

 that meaningful stewardship of the environment and 

 its biota extends beyond these simple (although of- 

 ten difficult to implement) criteria. Overexploiting 

 an ecosystem's productivity by overfishing (Russ, 

 1991) is just as detrimental as recruitment or 

 growth overfishing. 



Bohnsack (1991) recently applied the SLOSS con- 

 cept in a review of the function of artificial reefs. Obvi- 

 ously MFRs also can be evaluated in terms of SLOSS — 

 the question then may be, "Do several small reserves 

 potentially enhance SSB/R to the same extent as one 

 reserve of equivalent total size?" A realistic example 

 may be the relative fishery enhancement potential of 

 ten 1% closures versus one 10% closure. Establishing 

 a MFR of 10% may be impossible on a heavily popu- 

 lated island (like Oahu, Hawaii) where shoreline de- 

 velopment is near saturation. The siting of multiple, 

 smaller refuges, each about 1% of the total area, may 

 be feasible, however. But can a total closure of realis- 

 tic size (10%) be beneficial, and can the potential of 

 ten 1% closures approximate it? 



The simulation results suggest that a total closure 

 of 10% may enhance the spawning stock of a fast- 



