Seyoum et a\ : Genetic population structure in Saaenops ocellatus 



129 



Atlantic 

 Ocean 



Gulf of 

 Mexico 



FB 



Figure 1 



Sampling sites for red drum in waters off the southeastern United States. Florida: AP = 

 Apalachicola Bay; TB = Tampa Bay; OF = offshore, Tampa Bay; SA = Sarasota Bay; CH 

 = Charlotte Harbor; FB = Florida Bay; IR = Indian River; ML = Mosquito Lagoon; PO = 

 Ponce de Leon inlet; TP = Tomoka Basin. South Carolina: SC = Charleston Harbor. 



Third, are red drum in Mosquito Lagoon reproduc- 

 tively and genetically distinct or do they belong to 

 a larger and heretofore unsampled east Florida pop- 

 ulation? To examine these questions, we obtained 

 sequence data from the rapidly mutating mtDNA 

 control region. Sequencing the control region has 

 proven useful in intraspecific phylogeographic and 

 population genetic studies of fishes (e.g. Fajen and 

 Breden, 1992; Brown et al., 1993; Stepien, 1995; 

 Stabile et al., 1996). We employed sampling and 

 analytical regimes designed to test the various com- 

 peting hypotheses of red drum population structure. 

 In addition, by gathering baseline data for mtDNA 

 control region diversity in red drum populations, we 

 explored the potential for using the control region 

 as a marker to assess and monitor ongoing stocking 

 programs for wild red drum populations. 



Materials and methods 



Sample collection and DNA purification 



Samples of red drum were collected with hook-and- 

 line gear, trammel nets, and purse seines from riv- 



erine, estuarine, and offshore waters of the South 

 Carolina coast (one location) and the east coast 

 of Florida (four locations, sampled prior to stock 

 enhancement activities), referred to collectively as 

 the Atlantic samples; and the west coast of Florida 

 (six locations), referred to collectively as the Gulf sam- 

 ples (Fig. 1). All specimens were collected between 

 February 1992 and February 1997. Somatic muscle 

 and liver tissue were dissected from each individual. 

 Total length (range 280-1070 mm) of each individual 

 was recorded prior to dissection. Tissues were frozen 

 in liquid nitrogen and stored at -80°C in the labora- 

 tory until processing. 



Approximately 100—400 milligrams of muscle or 

 liver tissue were digested in 900 microliters of 

 lysis buffer (O.IM Tris, pH 8.0, 0.05M ethylenedia- 

 minetetraacetid acid (EDTA), 0.2M NaCl, 1% weight 

 by volume of sodium dodecyl sulfate (SDS), contain- 

 ing 1-2 milligrams of proteinase K) with moderate 

 shaking for 3-5 h at room temperature. Following 

 the addition of 150 microliters of chilled 8M potas- 

 sium acetate, the SDS and cellular debris were 

 precipitated for 30 min at A'C and removed by 

 centrifugation. Total genomic DNA was purified by 

 phenol/chloroform extraction ( Sambrook et al., 1989). 



