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Fishery Bulletin 92(4), 1994 



area of 1,807 km 2 or 0.5 canoes/km 2 ). Thus, present 

 estimates of MSY and f are on the order of 20- 

 30% of earlier estimates. 



Declining levels of CPUE, catch, and effort in the 

 south Jamaican fishery and lower estimates of sus- 

 tainable yield and effort all indicate that the pro- 

 ductivity of Jamaican reef fishes significantly de- 

 clined because of overfishing. The species composi- 

 tion of the trap fishery in the 1800's appears to have 

 been broadly similar to that off Belize today (Gosse, 

 1851). By 1968-71, when the first research surveys 

 on the south Jamaican shelf were carried out, the 

 catch was already dominated by relatively low-value 

 fish: the Haemulidae, Scaridae, and Acanthuridae 

 (Munro, 1983). By 1986, when these surveys were 

 repeated, overall CPUE had declined 33%. Several 

 families across a wide trophic range that represented 

 the bulk of the catch in 1968-71 had declined by more 

 than 50% (haemulids, small serranids, and acan- 

 thurids) or virtually disappeared (large serranids and 

 large scarids) (Koslow et al., 1988). The Holocentridae 

 and Pomacentridae were the only families that in- 

 creased significantly. Thus large segments of the 

 demersal fish community may be depleted on reefs 

 overfished by traps. This is in contrast to reefs ex- 

 ploited by more selective gear, such as spears that 

 target large piscivores, where a range of unfished or 

 lightly fished species may increase because of reduced 

 predation (Bohnsack, 1982). 



Several factors in addition to overfishing may have 

 contributed to the decline in productivity of Jamai- 

 can reefs. Pollution can be severe in the coastal zone 

 (Goodbody, 1989). There has been extensive reef dam- 

 age from hurricanes in recent decades. Reduced coral 

 production is associated with coral bleaching and 

 coral overgrowth by algae, which may be exacerbated 

 by the decline in herbivorous fishes, as well as by 

 eutrophication. 



Previous estimates of sustainable yield from the 

 south Jamaican shelf may have been biased upward. 

 An important assumption of the SPM is that the fish- 

 ery is at equilibrium, such that the reported catch 

 and effort are sustainable. The progressive decline 

 of the fishery indicates that previous yields were not 

 sustainable; therefore, estimates of MSY based on 

 those catch and effort data were likely inflated. 



Despite the progressive decline of the reef fish 

 fauna on the south Jamaican shelf over recent de- 

 cades, fishery assessments based on area-based 

 SPM's indicated that the region was underutilized 

 or only moderately exploited until as late as 1981 

 (Munro, 1978; Haughton, 1988). These analyses seem 

 to have been confounded by combining data from the 

 northern and southern Jamaican shelves without 

 normalizing for the -50^ lower density of productive 



habitat on the southern shelf. The level of exploitation 

 of the southern shelf relative to the northern shelf was 

 therefore underestimated by -50% (Fig. 5). 



At present, the reef fishery on the south coast of 

 Jamaica seems to be at the point of economic self- 

 regulation (Gordon, 1954), such that effort has de- 

 clined over the past decade owing to dramatically 

 declining catch rates as a result of over fishing. In 

 view of the general lack of opportunities in the Ja- 

 maican economy, an unmanaged reef fishery will re- 

 main heavily overfished and its productivity substan- 

 tially reduced. Present landings from the southern 

 shelf (0.5 t/km 2 of productive habitat) are approxi- 

 mately half the estimated potential MSY. 



Our estimate of MSY (0.5 t/km 2 of shelf) is at the 

 low end of estimates of maximum yield for reef fish- 

 eries in the Caribbean, which have generally ranged 

 from 0.5 to 1.5 t/km 2 (Munro, 1983; FAO, 1985). Glo- 

 bally, estimates of sustainable yield from reef fisher- 

 ies have ranged as high as 20 t/km 2 , although these 

 higher yields are generally from localized reefs rather 

 than from entire shelf areas (Russ, 1991). Thus there 

 may be a problem of standardization among studies. 



In conclusion, we had only limited success in de- 

 veloping an area-based SPM for Jamaican and 

 Belizean reef fisheries despite detailed surveys of 

 catch and effort and estimation of the proportion of 

 productive habitat in different areas. The difficul- 

 ties seemed to be attributable to the nonequilibrium 

 condition of the fisheries; the heterogeneous mix of 

 species both within and between the two countries; 

 the diversity of the fisheries that target a variety of 

 spawning, sedentary, and possibly migratory ani- 

 mals; and to possible differences in productivity 

 among sites. Thus the model's assumptions seem too 

 restrictive to permit meaningful analysis of catch and 

 effort data for such complex multispecies fisheries. 

 Violation of the model's assumptions, particularly the 

 nonequilibrium condition of the fishery, seems to have 

 led to serious bias in previous analyses of sustain- 

 able yield and effort for the Jamaican fishery. More 

 generally, these problems indicate that area-based 

 multispecies SPM's should be used cautiously in guid- 

 ing the future development of reef fisheries, unless 

 the model's assumptions can be shown to be reason- 

 ably satisfied. Nonetheless, the changes in catch com- 

 position and the sharp declines in CPUE, yield, and 

 estimated MSY in the Jamaican fishery over the past 

 decade, despite declining fishing effort, are indica- 

 tive of a severely overexploited fishery. 



Acknowledgments 



We thank the many people at the University of West 

 Indies, the Belize Fisheries Unit, and the Jamaica 



