Ault et a I.: A multispecies assessment of coral reef fish stocks 
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Figure 8 
Linear regressions of estimated species spawning potential ratio (y) 
on average 1996 Monroe County exvessel price (x) for: (A) snapper: y = 
119.59 - 41.38.x; and, ( B) grouper: y = 47.35 - 15.03*. 
Single-species fishery management models 
built to maximize fishery yield and economic 
rent ignore critical biological and physical 
interactions and cumulative stresses on 
habitats. Reef fish stocks are likely to be 
regulated by trophic interactions at the in- 
dividual, population, and community levels. 
Also, application of “traditional” fishery man- 
agement models developed for temperate spe- 
cies to tropical coral reef assemblages is tenu- 
ous. In response to these problems, the Na- 
tional Research Council Committee on Fish- 
eries (1994) recommended developing multi- 
species ecosystem management programs for 
building sustainable fisheries. Successful 
implementation of such programs will require 
innovative research, new management strat- 
egies, less destructive and wasteful fishing 
methods, protection of critical and sensitive 
habitats, and more effective education. 
Our retrospective analysis emphasized fish- 
ery-independent data. Although fishery-inde- 
pendent assessments can provide reliable 
measures of fish abundance, population dy- 
namics, and community composition ( Gunder- 
son, 1993), their application in multispecies 
fishery assessments have been limited. We 
predict an increasing need to rely on such data 
for assessment purposes because fishery-de- 
pendent data will become less available and 
less useful as new regulations are imposed 
that will establish larger size limits, closed 
seasons, closed fishing areas, and species pro- 
hibited from being fished. Also, the shifting 
emphasis from commercial to recreational 
fishing makes collecting fishery-dependent 
data much more difficult and expensive. 
Results from this 18-year retrospective assess- 
ment are encouraging in providing estimates of 
stock status. However, several assumptions that 
simplify the population dynamics of the various 
species make it prudent to consider population es- 
timates first-order approximations. The error intrin- 
sic in population-rate estimates derived from sur- 
veys depends on the accuracy and precision of the 
basic survey. Errors ultimately propagate upwards 
during a series of calculations used to determine 
the average size, total mortality rates, fishing mor- 
tality rates, yield-per-recruit, and finally the spawn- 
ing potential ratio, which is the current focus of 
management decisions. Also, although the Florida 
Keys fishery represents a major fishing area, it does 
not necessarily represent the entire stock range for 
an individual species. It is possible that mature 
stock components exist outside the fishing area. 
Six actions could improve future assessments. 
First, develop suitably structured spatial models for 
linkages between habitat use and fish ontogeny to 
“fill-in” the map of population estimates for areas 
not sampled. Second, calibrate the relative statisti- 
cal power of diver surveys and headboat fishing gear. 
Ideally, diver observations should relate to what fish- 
ermen catch. Because the fishing mortality rate of 
headboats (and viewing power of divers) are consid- 
ered strictly proportional to average population abun- 
dance, we must understand the fraction of the stock 
assessed per unit of effort and the interrelationship 
of the efficiency of the two “gear” types. Third, in- 
crease temporal and spatial sampling coverage to 
increase survey precision and resolution. Fourth, 
tune fishery-independent surveys with other indices 
of stock abundance. In this retrospective analyses, 
no attempt had been made to have the two survey 
