Seyoum et al.: Genetically determined population structure of Lachnolaimus maximus in the southeastern United States 
443 
al., 2008). This species supports a modest commercial 
fishery in the southeastern United States and is a 
highly valued target for recreational divers and spear 
fishermen (McBride and Murphy, 2003; FWC 1 ; NMFS 2 ). 
Hogfish occur in rocky and reef habitats, but those hab- 
itats are not continuous, and there are no studies that 
completely describe the continuity of their distribution 
along the Atlantic coast of the United States, let alone 
throughout their geographic range. 
The available data pertinent to stock structure of 
hogfish are limited to general behavioral and life his- 
tory patterns (e.g., Davis, 1976; McBride and Richard- 
son, 2007; Collins and McBride, 2011) and to a pre- 
liminary genetic survey of this species in the eastern 
Gulf of Mexico (MERPDC, 2012). Hogfish are broadcast 
spawners, a characteristic that facilitates dispersal of 
the propagules away from the spawning site (Colin, 
1982). The planktonic larval duration is 3-5 weeks 
(Colin, 1982; Victor, 1986), which is an average period 
among reef fishes (Victor, 1986; Leis et ah, 2013) and 
does not imply extensive mixing of genotypes between 
ocean basins. Moreover, hogfish maintain site fidelity 
and spawn in stable, site-specific harems (i.e., they 
do not migrate long distances to form spawning ag- 
gregations; Colin, 1982; Munoz et al., 2010), and there 
is evidence of reciprocal onshore larval dispersal and 
gradual offshore movement with growth (Collins and 
McBride, 2011). These behaviors have the potential to 
promote stock structure at a finer spatial scale than 
might be expected in an open marine ecosystem. 
Life history differences (e.g., maximum age, maxi- 
mum size, and fecundity) have been noted for hogfish 
in the eastern Gulf of Mexico and hogfish in south 
Florida (McBride et al., 2008), and variations also ex- 
ist among fish within the same region (McBride and 
Richardson, 2007; Collins and McBride, 2011, 2015). 
Hogfish grow older and larger, and spawn more eggs 
per female, in areas with lower fishing rates or in less 
gear-accessible habitats. Although these patterns af- 
fect vital rates within each region, they have not been 
linked to underlying biological stock structure (Collins 
and McBride 2011; McBride and Richardson, 2007; Mc- 
Bride et al., 2008; MERPDC, 2012; McBride, 2014b). 
Questions regarding the underlying stock structure 
were raised most recently in a request to review hog- 
fish stock structure and unit stock definitions as part 
of the most recent southeastern U.S. hogfish bench- 
mark assessment (Cooper et al. 3 ). 
The goal of this research was to use genetic data to 
determine whether more than one stock of hogfish ex- 
1 FWC (Florida Fish and Wildlife Conservation Commission). 
2013. Species account: Hogfish (Lachnolaimus maximus) in 
Florida, 4 p. [Available at website.] 
2 NMFS [National Marine Fisheries Service]. 2013. Commer- 
cial fisheries statistics. [Available at website.) 
3 Cooper, W., A. Collins, J. O’Hop, and D. Addis. 2014. The 
2013 stock assessment report for hogfish in the South Atlan- 
tic and Gulf of Mexico, 569 p. Fish Wildl. Res. Inst., Florida 
Fish Wildl. Conserv. Comm., St. Petersburg, FL. [Available 
at website.] 
ists in the southeastern United States and, if so, where 
the genetic breaks occur. We used microsatellite DNA 
markers, which are preferred over other types of mark- 
ers (e.g., allozymes and mitochondrial DNA) because 
of their ability to better detect the subtle genomic dif- 
ferences common among marine populations (Antoniou 
and Magoulas, 2014; Mariani and Bekkevold, 2014). 
Microsatellites are nuclear-encoded, codominant mark- 
ers that have characteristically high mutation rates 
and, hence, a high degree of allelic variation. These 
loci are scattered throughout the genome and can be 
influenced independently by recombination, selection, 
and drift; therefore, each locus is expected to have its 
own genealogical history that is slightly different from 
that of others. Adding and combining many loci makes 
a genomic sampling increasingly representative of the 
history of the previously described genetic processes 
and provides a robust method for investigating gene 
flow and population connectivity (Hedrick, 1999; Ka- 
linowski, 2002, 2005; Wilson and Rannala, 2003). Here 
we apply microsatellite loci previously isolated for hog- 
fish and optimized for routine assay (MERPDC, 2012) 
to specimens collected in an area from the Big Bend 
region of northwest Florida through North Carolina. 
Materials and methods 
Specimen collection and DNA extraction 
Specimens (N=719) were collected through intercepts 
of recreational and commercial spear fishermen or dur- 
ing directed research trips performed by biologists of 
the Fish and Wildlife Research Institute of the Florida 
Fish and Wildlife Conservation Commission. Specimens 
were identified according to Robins and Ray (1986) and 
were collected sporadically throughout the study area 
from November 2005 through August 2013. Fin clips 
were removed and preserved in 70% ethanol. Total 
DNA was isolated from approximately 500 mg of fin 
clip tissue with Gentra Puregene 4 DNA isolation kits 
(Qiagen, Valencia, CA) and rehydrated in 50 pL of de- 
ionized water. 
Collection locations were subdivided into 9 geo- 
graphic areas, referred to hereafter as sampling areas 
1-9 (Fig. 1). These sampling areas were identified pre- 
dominantly by latitude and coast (west [Gulf of Mexico] 
and east [Atlantic Ocean]) to delineate geographic re- 
gions corresponding to recognized faunal breaks, ma- 
jor estuaries, and (on a broader scale) management 
jurisdictions of hogfish. For example, faunal breaks are 
known to occur at Cape Romano (between sampling ar- 
eas 5 and 6), at Cape Sable (between sampling areas 
6 and 7), and at Cape Canaveral (between sampling 
areas 8 and 9) (Briggs and Bowen, 2012). Considerable 
estuarine flow onto the continental shelf occurs from 
4 Mention of trade names of commercial companies is for iden- 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
