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Fishery Bulletin 90(4). 1992 



for direct visualization, restriction digestions were 

 endlabeled before electrophoresis with a mixture of all 

 four 3^S nucleotide triphosphates using the Klenow 

 fragment (Maniatis et al. 1982). After electrophoresis, 

 gels were treated with a scintillation enhancer, dried, 

 and autoradiographs exposed at -70°C for 5 days. 

 Mitochondrial DNA was purified from YOY and 

 yearling bluefish collected in 1990 and 1991 following 

 the protocols of Lansman et al. (1981) and ^^S-end- 



labeled restriction fragments were visualized auto- 

 radiographically after electrophoresis. Due to the ther- 

 mal history of many of these specimens, yields of 

 supercoiled mtDNA were low. In those instances, the 

 nuclear band containing both nuclear DNA and relaxed 

 mtDNA was collected and dialyzed as described for 

 mtDNA bands in Lansman et al. (1981), or mtDNA was 

 reisolated following the Chapman and Powers (1984) 

 protocol. For these samples, the Southern transfer and 



