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Fishery Bulletin 113(4) 
tively broad geographic distance and separated by the 
land mass of peninsular Florida; therefore, genetic dif- 
ferentiation across this scale was not necessarily sur- 
prising (Riginos et al., 2011). The factors that influence 
stock separation are not known but are explored here 
from 3 perspectives: in relation to other coastal and 
marine fishes; at a seascape level (particularly in re- 
gard to the descriptive hydrodynamics around Florida), 
and in terms of how these results affect stock assess- 
ment and management of this species. 
In the western Atlantic Ocean, capes Romano and 
Canaveral have been identified previously as points of 
major shifts in marine animal community composition. 
Briggs and Bowen (2012) identified 1) Cape Romano as 
the point separating the marine community composi- 
tion of the Gulf of Mexico from that of the Caribbean 
province and 2) Cape Canaveral as separating the ma- 
rine community composition of the Caribbean province 
from that of the Carolinian province. Cape Romano 
was in fact the approximate point of the genetic break 
for hogfish in the eastern Gulf of Mexico in our study 
(cluster 1 versus cluster 2; Fig. 1). Unfortunately, the 
large geographic gap in hogfish collections between 
Cape Canaveral and South Carolina made it impos- 
sible to identify the point of the genetic break between 
clusters 2 and 3. 
Strong genetic differences between the Gulf and At- 
lantic coasts of Florida are known for several estua- 
rine and nearshore marine fishes, including common 
snook (Centropomus undecimalis) (Tringali and Bert, 
1996), red drum (Sciaenops ocellatus ) (Gold et al., 1999; 
Seyoum et al., 2000; Gold and Turner, 2002), and spot- 
ted seatrout ( Cynoscion nebulosus ) (Seyoum et al. 5 ). 
Strong genetic and phenotypic differences between the 
Gulf and Atlantic coasts of Florida are recognized for 
the shelf-dwelling reef fish black sea bass (Centropris- 
tis striata) (Bowen and Avise, 1990; McCartney et al., 
2013; McBride, 2014a). In contrast, only weak genet- 
ic differences have been found between the east and 
west coasts of Florida for other reef fishes, including 
red grouper ( Epinephelus morio), scamp ( Mycteroper - 
ca phenax) (Zatcoff et al., 2004), and vermilion snap- 
per ( Rhomboplites auroj'ubens ) (Tringali and Higham, 
2007). Similarly, there was little distinction between 
coasts for the pelagic king mackerel ( Scomberomorus 
cavalla) (Gold et al., 2002). Curiously, at least in the 
southeastern United States, the stock structure of hog- 
fish and black sea bass more closely resemble the stock 
structure of inshore and nearshore fishes (e.g., Seyoum 
et al. 5 ) than that of offshore reef fishes or large coastal 
pelagic fishes (e.g., Zatcoff et al., 2004). 
Hogfish reproduce in nearshore and offshore reef 
5 Seyoum, S., M. D. Tringali, B. L. Barthel, V. Villanova, C. Pu- 
chulutegui, M. C. Davis, and A. C. C. Alvarez. 2014. Stock 
boundaries for spotted seatrout (Cynoscion nebulosus) in 
Florida based on population genetic structure. Techni- 
cal Report TR-18, 27 p. [Available from Fish and Wildlife 
Research Institute, Florida Fish and Wildlife Conservation 
Commission, 100 Eighth Ave. SE, St. Petersburg, FL 33701- 
5020.] 
habitats on the continental shelf (depths of 10-70 
m; Colin, 1982; Collins and McBride, 2011). They are 
broadcast spawners who release buoyant eggs (Colin, 
1982), facilitating pelagic dispersal of propagules from 
the harem arenas. Early larvae raised in laboratory 
tanks formed bubbles around themselves while float- 
ing near the surface (Colin, 1982), a behavior that 
may also contribute to dispersal. The planktonic larval 
phase has been estimated to last for approximately 35 
days, preceding strong benthic orientation (Colin, 1982; 
Victor, 1986). Larvae are transported inshore, and ju- 
veniles settle in shallow, nearshore grass beds (Davis, 
1976; Colin, 1982). Therefore, cross-shelf (offshore-in- 
shore) dispersal of hogfish larvae is evident, but little 
is known about along-shelf dispersal. 
Hydrodynamic flow around Florida is complex (Liu 
and Weisberg, 2005), and dispersal of hogfish through- 
out this region is likely influenced by larval behavior 
and mortality (Cowen et al., 2000; Leis, 2006; Huebert 
et al., 2010). Although these are poorly understood for 
this species, a qualitative assessment indicates that 
northward and southward larval dispersal is like- 
ly along the western Florida shelf in particular. The 
peak spawning period for hogfish in the eastern Gulf 
of Mexico (March-May; McBride et al., 2008; Collins 
and McBride, 2015) occurs at a time when the currents 
are shifting from a predominantly southeasterly flow to 
a northwesterly flow (Liu and Weisberg, 2005, 2012). 
Hogfish spawning, however, occurs to some extent in 
most months (all except September) (Collins and Mc- 
Bride, 2015). Spawning throughout the year would sub- 
ject larvae to a diverse (and difficult to predict) set of 
conditions, both physical (e.g., temperature and season- 
al shifts in currents) and biological (e.g., prey availabil- 
ity through seasonal plankton blooms), that may affect 
dispersal vectors and survival rates (Cowen, 2002; Leis 
and McCormick, 2002). 
The Loop Current in the Gulf of Mexico is an up- 
stream portion of the Gulf Stream and affects differ- 
ent areas of the west Florida shelf to differing degrees 
throughout the year. Along the west Florida shelf, cur- 
rent flows are weakest near Cape Romano, and the low 
currents there may present a barrier to gene flow, as 
evident by the break between clusters 1 and 2; but cur- 
rent direction on the shelf also shifts seasonally from 
a southerly to northerly flow, and a strong looping cur- 
rent near the shelf break interacts periodically with 
local wind forces (He and Weisberg, 2003). The Loop 
Current presumably occurs beyond the range of hogfish 
spawning on the west Florida shelf (cluster 1; spawning 
occurs at <70 m; Collins and McBride, 2015), but the 
effects of this major current and its associated eddies 
are difficult to assess because many regional ichthyo- 
plankton surveys report taxa only to the family level 
or collect too few hogfish larvae for analysis (Richards 
et al., 1993; Huebert et al., 2010). 
Along the Atlantic side of the Florida Keys, the dom- 
inant current flow is to the east, fed by the Florida 
Current that flows through the Florida Strait and into 
the Gulf Stream. This current flow indicates that the 
