238 
Fishery Bulletin 109(2) 
100 
80 
60 
offshore 
nearshore 
40 - 
1 
0.0 
n I I 
0.4 0.6 
Sex ratio (M:F) 
08 
1.0 
Figure 4 
Frequency distribution of hogfish ( Lachnolaimus maximus) sex 
ratio nearshore (<30 m depth; n= 229 transects) and offshore 
(30-45 m depth; n = 54 transects) recorded during visual tran- 
sects. A value of 0.0 indicates that no males were observed; a 
value of 1.0 indicates that only males were observed. Sex ratios 
were not calculated for sites >45 m due to limited survey time. 
The spatially explicit demographic patterns 
evident within this study were not detected in 
previous research in the eastern Gulf of Mexico, 
probably because the data were analyzed in ag- 
gregate from collections over a broad geographic 
area (McBride and Richardson, 2007; McBride 
et al. 2008). These new results reveal distinct 
demographic structure across the shelf. Near- 
shore, hogfish occurred in higher densities and 
were younger, smaller, and slower growing than 
those offshore. Moreover, fish changed sex at a 
smaller size and younger age nearshore — per- 
haps as a response to social cues that maintain 
harem structure and increase spawning success. 
Given these facts, the potential would be great 
for fishing-induced genetic shifts, except for the 
existence of larger, faster growing fish offshore. 
Potential mechanisms are evaluated in the follow- 
ing sections to synthesize these ecological findings 
and elucidate the resilience of these reef fishes to 
fishing and environmental factors. 
Cross-shelf dynamics 
Spatial variation in demographic parameters is not 
unusual for widely distributed reef fishes (Gust, 
2004; DeVries, 2006; Allman, 2007; Lombardi- 
Carlson et al., 2008). It is likely that the underlying 
cross-shelf gradients of density and life history param- 
eters observed for hogfish reflect their bipartite life cycle. 
Hogfish are broadcast pair-spawners whose larvae are 
planktonic for 30-45 d (Colin, 1982) before settling in 
shallow inshore habitat such as seagrass beds (Roessler, 
1965; Victor, 1986; Lindeman et al., 2000). Along the 
west coast of Florida, juvenile hogfish use as nursery 
areas Tampa Bay, Charlotte Harbor, and the shallow 
inshore waters off Tarpon Springs and the Big Bend 
region (McMichael, unpubl. data 3 ). 
Ontogenetic migration offshore is suspected but is 
difficult to verify without tagging studies. Our research 
provides strong support for this hypothesis. Immature 
females were not collected from depths >22 m, and the 
youngest fish collected offshore (>30 m) was 2 years 
old, indicating that it takes at least two years to mi- 
grate from inshore settlement areas to offshore habitat. 
Although many reef fish have limited home ranges af- 
ter settlement (e.g., Williams et al., 1994), ontogenetic 
habitat shifts to deeper water are not uncommon (e.g., 
surgeonfish [Acanthurus chirurgus] and parrotfish [Sco- 
rns spp.], Nagelkerken et al., 2000; gag grouper [Myc- 
teroperca microlepis], Brule et al., 2003; gray snapper 
[Lutjanus griseus], Faunce and Serafy, 2007). 
It is likely that nearshore and offshore differences in 
maximum fish size and age were also, at least partially, 
related to the persistent, severe red tide ( Karenia bre- 
vis) that occurred off the west coast of Florida during 
3 McMichael, Robert. 2011. Unpubl. data. Fish and Wildlife 
Research Institute, Fisheries-independent monitoring group, 
100 8th Avenue SE, Saint Petersburg, Florida 33701. 
2004-05, the year before this study began. Nearshore 
benthic communities in the study area suffered sig- 
nificant mortality during and following that red tide 
(Landsberg et al., 2009), when widespread fish kills and 
dead or reduced benthic fauna were reported in waters 
<30 m deep off Tampa Bay (Hu et al., 2006; Gannon 
et al., 2009). 
During the last red tide outbreak of similar severity 
(in 1971), hogfish died or were displaced from many 
reefs in 13-30 m (Smith, 1975) but recolonized the af- 
fected areas within 4-10 months (Smith, 1979). Smith 
did not report length data, and therefore it was not 
possible to identify whether the source of recovery was 
new recruits or transient fish from unaffected reefs. 
Our findings regarding nearshore demographics may 
partially reflect the recovery of the population in that 
area after a major (but uncommon) toxic event. 
Resiliency to localized environmental perturbations 
such as red tides is likely related to a species’ distribu- 
tion over a wide geographical range. The existence of 
large individuals in deep water offshore should provide 
a reservoir of spawning individuals to help replenish 
inshore areas (e.g., Simberloff, 1974). Although there 
were no reef-specific demographic data for the study 
area before the 2005 red tide, local divers recalled that 
the hogfish in shallow water were larger and more 
abundant before the toxic event. Additionally, greater 
numbers of relatively larger hogfish have been observed 
in shallow waters during research dives performed 
since the completion of this study (senior author, un- 
publ. data). 
The pronounced size and age truncation observed 
nearshore is also likely related to greater fishing mor- 
