767 
AbStraCt-Variation in restriction 
sites of mitochondrial (mt)DNA was ex- 
amined from 444 greater amberjack 
( Seriola dumerili) sampled from 11 off- 
shore localities in the northern Gulf of 
Mexico (Gulf) and along the U.S. south- 
east Atlantic coast (Atlantic). A total of 
49 mtDNA haplotypes (genotypes) were 
detected. Percent nucleotide sequence 
divergence among the haplotypes 
ranged from 0.156 to 2.623 (mean 
±SE=0.980 ±0.015). Nucleon diversity 
within samples ranged from 0.845 to 
0.906, and inirapopu laticnai mtDNA 
diversities ranged (mean ±SD) from 
0.483 ±0.370 to 0.619 ±0.419. The lat- 
ter did not differ significantly from one 
another. Homogeneity tests of mtDNA 
haplotype frequencies, F ST values, analy- 
sis of molecular variance (AMOVA), and 
comparisons of pairwise dy r distances 
were consistent with the hypothesis 
that (at least) two subpopulations 
(stocks) of greater amberjack exist in 
U.S. waters: one in the northern Gulf 
and one along the U.S. Atlantic coast. 
The latter subpopulation includes in- 
dividuals from the Florida Keys. There 
was no evidence of phylogeographic 
structure among mtDNA haplotypes or 
among sample localities, suggesting 
either that restricted gene flow between 
the subpopulations is fairly recent or 
that gene flow between the two is rela- 
tively infrequent. No significant spatial 
autocorrelations of mtDNA haplotypes 
was found among samples of greater 
amberjack from the Gulf, indicating 
continuous gene flow across the north- 
ern Gulf. Long-term effective (female) 
population sizes of both subpopulations 
were estimated to be in the range of 
90,000-95,000 individuals. The esti- 
mates were commensurate with esti- 
mates in other, economically important 
marine fish. Based on suggested differ- 
ences in mtDNA evolutionary rates be- 
tween homeothermic and poikilother- 
mic vertebrates, the effective (female) 
population sizes of both stocks of 
greater amberjack could be in the range 
of 500,000 to 1,000,000 individuals. 
Manuscript accepted 13 March 1998 
Fish. Bull. 96:767-778 (1998). 
Population structure in greater 
amberjack, Seriola dumerili, 
from the Gulf of Mexico and the 
western Atlantic Ocean* 
John R. Gold 
Linda R. Richardson 
Center for Biosystematics and Biodiversity 
Department of Wildlife and Fisheries Sciences 
Texas A&M University 
College Station, Texas 77843-2258 
E-mail address: goldfish@tamu.edu 
Greater amberjack, Seriola dumerili, 
constitute an increasingly important 
component of the U.S. Gulf and At- 
lantic commercial and recreational 
fisheries. Commercial landings in 
the Atlantic rose over twentyfold 
between 1981 and 1991, from un- 
der 100,000 pounds annually to 
nearly two million pounds (Cum- 
mings-Parrack * 1 ). Commercial land- 
ings in the Gulf rose similarly, 
reaching a peak of nearly 2.5 mil- 
lion pounds in 1988 that was then 
followed by a >50% decline in 1990 
and a further decline in 1991 
(McClellan and Cummings 2 ). An 
increase in commercial landings in 
1993 was followed by declines in 
both 1994 and 1995 (McClellan and 
Cummings 2 ). The commercial inter- 
est in greater amberjack appears to 
be driven by: 1) consumer accep- 
tance of greater amberjack as an 
edible fish; 2) replacement of red 
drum in the blackened fish market; 
and 3) effort displacement of king 
mackerel and reef-fish fishermen, 
especially off the coasts of Florida 
(Cummings-Parrack 1 ). Recreational 
landings are smaller in both the 
Gulf and Atlantic and appear to 
have declined in recent years (Cum- 
mings-Parrack 1 ; McClellan and 
Cummings 2 ). Problems that con- 
found landing statistics and fishery 
analysis of the greater amberjack 
resource include species misidenti- 
fication and the possibility that re- 
ported landings may be small in 
proportion to total removals (Cum- 
mings-Parrack 1 ). Current manage- 
ment of the greater amberjack re- 
source in U.S. waters is based on a 
two-stock (management unit) model. 
One stock resides along the U.S. 
southeastern coast and includes all 
fishing areas north of Cape Hatteras, 
NC (35°0G'N) southward to the Dry 
Tortugas and the Florida Keys 
(24°35'N); the other includes fish- 
ing grounds in the Gulf of Mexico 
off the Dry Tortugas and Florida 
Keys north and then westward to 
the U. S. Mexico border (26°00'N) 
* This paper represents xx in the series “Ge- 
netic studies in marine fishes” and contri- 
bution number 67 of the Center for Bio- 
systematics and Biodiversity at Texas 
A&M LTniversity, College Station, Texas 
77843-2258. 
1 Cummings-Parrack, N. 1993. The ex- 
ploitation status of the Atlantic amberjack 
fisheries through 1991. Miami Laboratory, 
SE Fisheries Sci. Center, Natl. Mar. Fish. 
Serv., Cont. MIA-92/93-30, Miami, FL, 98 p. 
2 McClellan, D. B., and N. J. Cummings. 
1996. Stock assessment of Gulf of Mexico 
greater amberjack through 1995. Miami 
Laboratory, SE Fisheries Sci. Center, Natl. 
Mar. Fish. Serv., Cont. MIA-96/97-03, Mi- 
ami, FL, 69 p. 
