Gold and Richardson: Population structure of Seriola dumerili 
111 
The two estimates do not differ significantly from 
one another and are larger than those reported in a 
more limited (in terms of sample size and geographic 
coverage) study of greater amberjack (Richardson 
and Gold, 1993). They also are commensurate with 
N„ , estimates for several other marine fish of com- 
fie) 
mercial or recreational value (Gold et ah, 1993). Al- 
though a positive correlation exists between effec- 
tive population sizes and census sizes, the latter are 
generally an order of magnitude or two larger than 
the former (Avise et ah, 1988). One reason for this 
difference, at least in estimates of N f}g) values for 
poikilothermic vertebrates, is that the models of Avise 
et al. (1988) employ (estimated) mtDNA evolution- 
ary rates for homeothermic vertebrates. Estimated 
mtDNA evolutionary rates for poikilothermic verte- 
brates may be 5-10 times less than those for homeo- 
thermic vertebrates (Martin and Palumbi, 1993), 
suggesting that long-term effective population sizes 
of each subpopulation of greater amberjack could be 
on the order of 500,000 to 1,000,000 females. 
According to results of this project, current stock 
boundaries for assessment and allocation of greater am- 
beijack resources in U.S. waters appear appropriate 
except possibly for the west coast of Florida, south of 
the Florida Middle Ground. Depending on present or 
future importance of the greater amberjack fishery in 
this area, it would be useful to know both the geographic 
limits of the two subpopulations and whether the 
Florida Keys constitute a mixing zone for greater am- 
beijack as for species such as king mackerel. 
Acknowledgments 
We thank J. Bielawski, D. Codella, C. Denis, K. Dunn, 
D. Fable, J. Franks, Jer. Gold, Jes Gold, E. Gricius, 
C. Grimes, E. Heist, P. Hood, J. Magursky, C. 
Ragland, and B. Thompson for assistance in procur- 
ing specimens, and N. Cummings and T. Turner for 
comments on the manuscript. Work was supported 
by the Saltonstall-Kennedy Program of the U.S. De- 
partment of Commerce (Award NA57FD-0-069-01), 
as administered by the National Marine Fisheries 
Service, and by the Texas Agricultural Experiment 
Station under Project H-6703. Part of the work was 
carried out in the Center for Biosystematics and 
Biodiversity, a facility funded, in part, by the Na- 
tional Science Foundation (Award DIR-89-07006). 
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