71 
Abstract— Long-term sustainable man- 
agement of wild populations should be 
based on management actions that ac- 
count for the genetic structure among 
populations. Knowledge of genetic 
structure and of the degree of demo- 
graphic exchange between discreet 
populations allows managers to bet- 
ter define management units. However, 
adequate gene loci for population as- 
sessments are not always available. In 
this study, variable co-dominant DNA 
loci in the heavily exploited marine 
genus Brevoortia were developed with 
a microsatellite-enriched DNA library 
for the Gulf Menhaden (Brevoortia pa- 
tronus). Microsatellite marker discov- 
ery was followed by genetic character- 
ization of 4 endemic North American 
Brevoortia species, by using 14 novel 
loci as well as 5 previously described 
loci. Power analysis of these loci for 
use in species identification and genet- 
ic stock structure was used to assess 
their potential to improve the stock 
definition in the menhaden fishery of 
the Gulf of Mexico. These loci could 
be used to reliably identify menhaden 
species in the Gulf of Mexico with an 
estimated error rate of a=0.0001. Simi- 
larly, a power analysis completed on 
the basis of observed allele frequen- 
cies in Gulf Menhaden indicated that 
these markers can be used to detect 
very small levels of genetic divergence 
</ r s t=0.004) among simulated popula- 
tions, with sample sizes as small as 
n = 50 individuals. A cursory analysis 
of genetic structure among Gulf Men- 
haden sampled throughout the Gulf 
of Mexico indicated limited genetic 
structure among sampling locations, 
although the available sampling did 
not reach the target number (n= 50) 
necessary to detect minimal values of 
significant structure. 
Manuscript submitted 14 February 2013. 
Manuscript accepted 6 December 2013. 
Fish. Bull. 112:71-81 (2014). 
doi: 10.7755/FB.112.1.5 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necesarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Limited genetic structure of Gulf Menhaden 
( Brevoortia patron us), as revealed by 
microsatellite markers developed for the 
genus Brevoortia (Clupeidae) 
Joel D. Anderson (contact author) 
William J. Karel 
Email Address for contact author: joel.anderson@tpwd.state.tx.us 
Perry R. Bass Marine Fisheries Research Station 
Texas Parks and Wildlife Department 
3862 FM 3280 
Palacios, Texas 77465 
Management of wild populations is 
improved when management actions 
take into account genetic structure. 
Stock assessments of marine species 
are improved when genetic data are 
used in the development of a fishery 
stock definition (Begg and Waldman, 
1999; Waples et ah, 2008). Different 
outcomes in stock assessments are 
expected between a scenario with 
a single exploited population and a 
scenario in which 2 or more demo- 
graphically independent populations 
are exploited simultaneously by a 
fishery. In the latter case, treating 2 
or more independent fishery stocks 
as a single unit could potentially 
lead to underestimates of the effects 
of exploitation on local stocks and an 
overall diminished yield (Carvalho 
and Hauser, 1994). Therefore, genetic 
analyses of population structure can 
improve stock assessments by in- 
creasing accuracy in identification of 
the number of populations exploited 
and the extent and direction of demo- 
graphic exchange (migration) among 
exploited populations (Begg and 
Waldman, 1999; Waples et al., 2008). 
A recent Southeast Data, Assess- 
ment, and Review (SEDAR) stock as- 
sessment indicated that more genetic 
data are needed to appropriately de- 
fine the stock harvested by the men- 
haden fishery (Brevoortia spp.) in the 
Gulf of Mexico (Vaughn et al. 1 ). Two 
1 Vaughn, D., A. Schueller, J. Smith, and S. 
VanderKooy (eds.). 2011. SEDAR 27: 
Stock assessment report. Gulf of Mexico 
aspects of the stock definition for the 
menhaden fishery can be improved 
with genetic data. First, the men- 
haden catch in the Gulf of Mexico is 
thought to consist of 3 species: Gulf 
Menhaden ( Brevoortia patronus), Fi- 
nescale Menhaden (B. gunteri), and 
Yellowfin Menhaden (B. smithi). Ahr- 
enholz (1981) suggested that 99% of 
the catch comprised Gulf Menhaden, 
but this finding can be re-assessed 
with sampling of diagnostic micro- 
satellite DNA loci. Second, infor- 
mation about population structure 
within the species targeted by the 
fishery, Gulf Menhaden, will result 
in a better definition of management 
units that compose the stock (Waples 
et al., 2008). A more suitable stock 
definition in turn will result in more 
practical biological reference points 
in stock assessments. Previous 
studies of population structure in 
Gulf Menhaden have indicated that 
there is a single stock in the Gulf of 
Mexico, but these studies were com- 
pleted with sampling designs that 
were not specifically intended to as- 
sess fine-scale population structure 
among locales in the Gulf of Mexico 
(Bowen and Avise, 1990; Anderson, 
2007; Anderson and Karel, 2007). A 
major downfall of these studies has 
been a paucity of adequate gene loci 
developed for the genus Brevoortia, 
menhaden, 460 p. Southeast Data, As- 
sessment, and Review, Charleston, SC. 
[Available from http://www.sefsc.noaa. 
gov/sedar/Index.jsp.] 
