416 
Population structure, long-term connectivity, 
and effective size of mutton snapper 
( Lutjanus analis) in the Caribbean Sea 
and Florida Keys 
Evan W. Carson’ 
Eric Saillant 2 
Mark A. Renshaw’ 
Nancie J. Cummings 3 
John R. Gold (contact author ) 1 
Email address for contact author: goldfish@tamu.edu 
' Center for Biosystematics and Biodiversity 
Texas A and M University 
College Station, Texas 77843-2258 
2 Department of Coastal Sciences 
Gulf Coast Research Laboratory 
The University of Southern Mississippi 
703 East Beach Drive 
Ocean Springs, Mississippi 39564 
3 National Marine Fisheries Service 
Southeast Fisheries Science Center 
75 Virginia Beach Drive 
Miami, Florida 33149 
Abstract — Genetic structure and 
average long-term connectivity and 
effective size of mutton snapper (Lut- 
janus analis) sampled from offshore 
localities in the U.S. Caribbean and 
the Florida Keys were assessed by 
using nuclear-encoded microsatel- 
lites and a fragment of mitochondrial 
DNA. No significant differences in 
allele, genotype (microsatellites), 
or haplotype (mtDNA) distributions 
were detected; tests of selective neu- 
trality (mtDNA) were nonsignificant 
after Bonferroni correction. Heuristic 
estimates of average long-term rate 
of migration (proportion of migrant 
individuals/generation) between geo- 
graphically adjacent localities varied 
from 0.0033 to 0.0054, indicating that 
local subpopulations could respond 
independently of environmental per- 
turbations. Estimates of average long- 
term effective population sizes varied 
from 341 to 1066 and differed signifi- 
cantly among several of the localities. 
These results indicate that over time 
larval drift and interregional adult 
movement may not be sufficient to 
maintain population sustainability 
across the region and that there may 
be different demographic stocks at 
some of the localities studied. The 
estimate of long-term effective popu- 
lation size at the locality offshore of 
St. Croix was below the minimum 
threshold size considered necessary 
to maintain the equilibrium between 
the loss of adaptive genetic variance 
from genetic drift and its replacement 
by mutation. Genetic variability in 
mutton snapper likely is maintained 
at the intraregional level by aggregate 
spawning and random mating of local 
populations. This feature is perhaps 
ironic in that aggregate spawning also 
renders mutton snapper especially 
vulnerable to overexploitation. 
Manuscript submitted 11 April 2011. 
Manuscript accepted 18 July 2011. 
Fish. Bull. 109:416-428 (2011). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
An understanding of the genetic 
structure of exploited, reef-associ- 
ated marine fish species is important 
for their effective conservation and 
management. Many such species are 
known to have long larval phases 
(Boehlert, 1996) — a trait associated 
with either genetic cohesion or con- 
nectivity across regional geographic 
scales (Shulman and Bermingham, 
1995; Rocha et al., 2002). However, 
many of these species also form stable 
spawning aggregations where assem- 
blages of individuals gather in large 
densities with the specific purpose 
of reproducing, generally at approxi- 
mately the same time and place each 
year (Domeier and Colin, 1997). For 
geographically widespread species, 
multiple spawning aggregations could 
tend to minimize connectivity at 
regional scales if adult movements are 
intraregionally localized. This effect 
would be pertinent to management of 
heavily exploited groups such as snap- 
pers and groupers in which spawn- 
ing aggregations are common (Claro 
and Lindeman, 2003). Because fish- 
ing efforts commonly target spawning 
aggregations, participating species 
are at elevated risk of overexploita- 
tion and rapid population depletion 
(Domeier and Colin, 1997; Domeier, 
2004; Sadovy de Mitcheson et ah, 
2008). Knowledge of population struc- 
ture is thus of importance because 
separate management of subregional 
stocks, should they exist, is critical 
both to avoid over-exploitation and to 
maintain potentially adaptive genetic 
variation (Carvalho and Hauser, 1995; 
Hauser and Ward, 1998). Recent pop- 
ulation-genetic studies of species that 
participate in spawning aggregations 
have included assessment of genetic 
variation (Rhodes et ah, 2003) and the 
relationship between effective popula- 
tion size (N e ) and census size (Bek- 
kevold et al., 2002). 
In this study, we assessed genetic 
structure and average long-term con- 
nectivity and effective size of mutton 
snapper (Lutjanus analis) sampled 
from four localities in the northeast- 
ern Caribbean Sea and one locality 
in the Florida Keys. Mutton snap- 
per are an important component of 
commercial fisheries in this region 
