NOTE Sluka and Sullivan: Spear fishing on species composition and size of groupers on reefs 
391 
the smaller number of spear fishermen. However, the 
lower number of spear fishermen may exert a more 
directed selectional effect on grouper species because 
they can be highly selective for the largest individuals. 
The growth and reproductive characteristics of 
groupers render these species especially susceptible 
to overfishing (Bannerot et al., 1987; Shapiro, 1987; 
Huntsman and Schaaf, 1994). Groupers that are tar- 
geted by fishing grow slowly to a large maximum size 
(Manooch, 1987). The removal of larger individuals 
leaves behind smaller individuals to spawn. Over 
many generations, this can result in a decrease in 
the size and age at sexual maturity (Ricker, 1981) 
and also decrease the average size of the population 
(Roberts and Polunin, 1991). Many grouper species 
are protogynous hermaphrodites, changing sex from 
females to males later in life (Shapiro, 1987). Larger 
groupers are generally males, and at intensive fish- 
ing levels, the number of males in the population can 
be drastically reduced. If too many males are re- 
moved, sperm are reduced for reproduction (Bannerot 
et al., 1987). If sperm are reduced, protogynous stocks 
are more vulnerable to overfishing than are gono- 
choristic stocks (Huntsman and Schaaf, 1994). Spe- 
cies that are protogynous may experience a drastic 
reduction in reproductive capacity, even at moder- 
ate levels of fishing (Huntsman and Schaaf, 1994). 
However, there may be mechanisms by which the 
population can compensate for a changing sex ratio 
in the presence of overfishing (Claro et al., 1990; 
Huntsman and Schaaf, 1994). Huntsman and Schaaf 
(1994) showed that these types of compensation 
mechanisms can reduce the detrimental impacts of 
fishing pressure on protogynous species. In addition 
to protogyny, the reproductive behavior of groupers 
may increase their susceptibility to overfishing. Many 
species of grouper aggregate to spawn during one or 
two months of the year (Smith, 1972; Shapiro, 1987; 
Claro et al., 1990). These spawning aggregations are 
subject to intense fishing pressure (Olsen and 
LaPlace, 1978, Claro et al., 1990; Sadovy, 1994). In 
many parts of the Caribbean, aggregations have dis- 
appeared as a result of overfishing (Sadovy, 1994). 
Sluka et al. (1997) showed that reproduction (the 
total number of eggs produced per hectare) was six 
times greater in a marine fishery reserve in the cen- 
tral Bahamas than in the surrounding unprotected 
region. 
It is concluded that the ban on spear fishing in the 
upper Florida Keys has significantly benefitted the 
size distribution of groupers. However, it appears that 
a ban on spear fishing alone has not resulted in re- 
covering population levels of grouper in this region. 
Bohnsack et al. (1994) has clearly shown a decline 
in commercially and recreationally targeted grouper 
landings throughout the Florida Keys. Sluka and 
Sullivan (1996) have shown that the offshore grou- 
per assemblage over shallow bank reefs of the upper 
Florida Keys is dominated numerically by graysby 
(88%), a small, nontargeted species. Densities of tar- 
geted species are low compared with regions where 
fishing was prohibited or had not yet taken place 
(Sluka and Reichenbach, 1996; Sluka et al., 1997). 
It is recommended that marine fishery reserves 
be considered as a management measure because of 
their success in other regions and because of a strong 
theoretical basis (PDT, 1990). Grouper assemblages 
inside marine fishery reserves are more dense, of 
greater average size, and produce greater numbers 
of eggs per hectare than in similar, unfished sites 
(Bohnsack, 1982; Russ and Alcala, 1989, Roberts and 
Polunin, 1993; Watson and Ormond, 1994; Sluka et 
al.,1997). Although management measures, such as 
bans on spear fishing, have some beneficial effects, the 
available evidence suggests that the establishment of 
marine fishery reserves is the most successful method 
for restoring and conserving grouper assemblages. 
Acknowledgments 
The authors would like to thank the staff of the Na- 
tional Undersea Research Program Florida Keys 
Program for logistical support. Fieldwork was as- 
sisted by M. Chiappone, T. Potts, G. Meester, and J. 
Levy. Figure 1 was prepared by R. Wright. This re- 
search was funded by NOAA’s National Undersea 
Research Program under NURC/UNCW grant 
UNCW-9420 to K.M. Sullivan and was conducted in 
the Florida Keys under National Marine Sanctuary 
Permit 93-27. Support was also obtained from Uni- 
versity of Miami (Department of Biology) and The 
Nature Conservancy’s Florida Keys Initiative and 
Caribbean program. Research was conducted as part 
of a doctoral dissertation completed by R. Sluka at 
the University of Miami. This manuscript benefit- 
ted significantly from readings by J. Bohnsack, S. 
Bolden, N. Ehrhardt, J. Prince, C. R. Robins, and 
three anonymous reviewers. 
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