DeMartini: Potential of fishery reserves for managing Pacific coral reef fishes 



423 



inconclusive: Alcala and Russ's 

 (1990) observations of an effect 

 on reef fish catches adjacent to 

 the Sumilon Island reserve were 

 from a series of years in which 

 the reserve operated and from 

 only one year of reduced catches 

 that began 18 months after the 

 reserve's protected status ended. 

 Catches were dominated by one 

 taxon (fusiliers, family Caesi- 

 onidae; 659c of total) that used 

 the reef for nocturnal shelter but 

 whose zooplankton prey may 

 have been unrelated to reef area 

 (Alcala and Russ, 1990). Brief 

 changes in yield, rather than 

 Y/R, particularly on a small 

 (0.5 km 2 ) spatial scale, may rep- 

 resent nonequilibrium phenom- 

 ena (e.g., lagged effects on adult 

 abundance resulting from a lo- 

 calized change in recruitment). 

 Alcala and Russ's (1990) obser- 

 vations therefore are not neces- 

 sarily inconsistent with simula- 

 tion results (see Russ et al, in 

 press). 



Clearly, additional empirical 

 measures are needed for Y/R 

 as well as SSB/R of fishery re- 

 sources in exploited regions ad- 

 jacent to MFRs. For the present 

 discussion, however, this paper 

 will focus on simulated SSB/R 

 results. 



even larger countering effect (Fig. 5). The effect of com- 

 pensatory rate adjustments apparently varied with fish 

 type in a manner not directly related to fundamental 

 transfer rate. When the surgeonfish and jack were each 

 evaluated using T u - 0.1 as the fundamental rate, 

 compensatory dampening in the rate of SSB/R gain 

 at larger refuge sizes was less for the surgeonfish ( Fig. 

 5A) than for the jack (Fig. 5B). 



Discussion 



MFRs and enhanced Y/R 



Simulations to date suggest that MFRs have the poten- 

 tial to augment SSB/R, but enhance Y/R little, if at 

 all, in adjacent non-closed areas (Polacheck, 1990; the 

 present study). The only empirical study to date was 



Relative influences of input parameters 



Growth rate is a major influence of biomass accrual 

 within refuges (Polacheck, 1990), as fast-growing fish 

 can elaborate more surplus production (yield) per unit 

 time and unit area of refuge than can slow-growing 

 fish. And since growth and mortality rates are linked, 

 it is not surprising that mortality rate is important, as 

 fishes with a higher natural mortality can support 

 fisheries in which they are harvested more heavily 

 and earlier in life than can fishes with a lower mortal- 

 ity rate. 



In the basic yield model, the effects of natural mor- 

 tality and level of exploitation overwhelm those of age 

 at first capture. Proportional changes in rates obvi- 

 ously have larger effects than equal-sized changes in 

 the time period over which the rates apply. Of greater 

 interest here are the relative magnitudes of the effects 



