Collins and McBride: Spatially explicit life-history dynamics of a protogynous reef fish 
239 
tality associated with increased accessibility of 
fish to fishing vessels. Hogfish feed on slow mov- 
ing, benthic invertebrates (Randall and Warmke, 
1967) and are less vulnerable to hook-and-line 
fishing methods than most other reef species in 
the region. Consequently, they are harvested pri- 
marily by spearfishing. Most recreational diving 
is done at depths <130 ft (40 m; PADI, 1999); at 
greater depths a diver’s bottom time is limited 
and restricted to divers with higher skill levels. 
Additionally, because deep sites are farther from 
shore, fuel expense and travel time are greater. 
Together, these factors potentially contribute to 
decreased fishing-induced mortality of hogfish 
offshore. Tupper and Rudd (2002) noted a similar 
pattern in the Caribbean, where larger hogfish 
were present in deeper and unfished areas. This 
pattern has also been observed for other species 
in the Gulf of Mexico. Gray triggerfish ( Balistes 
capriscus ) exhibit decreasing mortality with in- 
creasing distance from shore (Ingram, 2001), and 
vermillion snapper ( Rhomboplites aurorubens ) 
display a spatial size dichotomy that has been 
related to higher exploitation rates within waters 
closer to shore (Allman, 2007). 
Notably different patterns of sex change were 
observed for nearshore and offshore regions. In 
aggregate, sex change occurred over a broad 
range of ages and sizes (1-11 years and 197-727 
mm FL), indicating that it is likely to be under 
social control (e.g., removal of the dominant male 
initiates sex change in a large female). The size 
advantage model predicts that sexual transition 
will occur at an earlier age in populations expe- 
riencing higher mortality (Warner, 1988), and 
it has often been observed that the continued 
removal of males results in reduced size at sex 
change and that size and age at the onset of sex 
change are lower in areas of greater fishing pres- 
sure (Warner 1975; Hawkins and Roberts, 2003; 
Hamilton et al., 2007). The smaller size and younger 
age of hogfish at sex change indicates shorter life spans 
and greater mortality in nearshore waters. 
In this study, median size at sex change nearshore 
(327 mm FL) just exceeded the legal minimum size (305 
mm FL). These data indicate that many nearshore fe- 
males are changing sex within one year after reaching 
legal size, since hogfish take about one year to complete 
sex change (McBride and Johnson, 2007). The probabil- 
ity of moving offshore may be related to an individual’s 
growth rate because hogfish of the same age were larger 
offshore than nearshore. These faster-growing fish may 
have had greater energy reserves (perhaps by delaying 
sex change), allowing successful migration offshore. 
Alternately, resource (e.g., food, habitat) availability 
or another environmental factor may have allowed for 
faster growth within deeper habitat. The higher den- 
sities observed nearshore may result in an increased 
competition for food; however, a qualitative assessment 
of stomach fullness (stomach weight divided by total 
0 2 4 6 8 10 12 14 16 18 20 22 
Age (years) 
Figure 5 
Hogfish (Lachnolaimus maximus ) fork length (FL) at age for 
(A) nearshore (<30 m), and (B) offshore (>30 m) collections. 
Gonad histology determined sexual classification as female 
(classes 1-4), transitional or immature male (classes 5-6), or 
mature male (classes 7—10). Estimated von Bertalanffy growth 
parameters: L^= 380.5 mm, K= 0.5614 and t 0 =-0.1619 (near- 
shore) and L m = 896 mm, 7f=0.0940 and t 0 =-1.9752 (offshore). 
body weight) did not show any relationship with depth. 
A more quantitative assessment of prey availability 
and prey quality should be performed to address this 
question. 
It is possible that differences in life history traits 
could reflect genetically distinct populations. Although 
this scenario was considered unlikely (because of the 
absence of immature hogfish offshore), DNA samples 
were collected from a subsample of individuals from 
both depth ranges (n = 82; authors of this article, un- 
publ. data). Preliminary genetic analysis of microsatel- 
lite loci provided no evidence of separate stocks in our 
sampling area (Seyoum, unpubl. data 4 ). The level of 
analysis available at this time cannot completely ex- 
clude the possibility, but it seems unlikely. 
4 Seyoum, Seifu. 2011. Unpubl. data. Fish and Wildlife 
Research Institute, 100 8th Avenue SE, Saint Petersburg, 
Florida 33701. 
