374 



Fishery Bulletin 97(2), 1999 



ln(Hg) = -1.57 + 0.0016 (PCL) 



500 600 700 800 900 1.000 1.100 1.200 

 Precaudal length (mm) 



Figure 1 



Relation between In total mercury level (ppm) and 

 precaudal length (mm) for juvenile bull sharks. 

 Carcharhinus leucas. from the Atlantic coast of 

 Florida. 



(x=0.77 ppm; me(dian=0.44 ppm) (Table 1). Mean 

 total mercury levels for females (x=0.87 ppm) were 

 higher than those for males (.v=0.58 ppm): however, 

 these (differences were not analyzed for statistical 

 significance because sample sizes were small (« = 14 

 females; n=7 males). The female blacktip sharks col- 

 lected in this study were larger (.r =994.3 mm PCL) 

 than the males (.r=830.1 mm PCL). Almost half 

 (47.6'^) of the blacktip sharks examined had mer- 

 cury levels that were greater than or equal to the 

 0.5-ppm threshold level. The four blacktip shark 

 embryos (x=235 mm PCL), collected from a single 

 1050-mm-PCL female whose total mercury level was 

 2.3 ppm, had total mercury levels ranging from 0.63 to 

 0.78 ppm (.r=0.69 ppm; median=0.68 ppm) (Table 2). 



Mercury levels in these embryos equaled 27.4-33.9% 

 of levels observed in their mother. 



There was a significant positive correlation be- 

 tween total mercury level and blacktip shark length 

 (both sexes combined)(P<0.0001; Fig. 2). Total mer- 

 cury levels in blacktip sharks increased as individu- 

 als grew larger, although some small sharks con- 

 tained levels as high as those in larger sharks. 



Atlantic sharpnose shark, Rhizoprionodon 

 terraenovae 



Total mercury levels for 81 juvenile and adult Atlan- 

 tic sharpnose sharks ranged from 0.11 to 2.3 ppm 

 (.V = 1.06 ppm; median=0.95 ppm) (Table 1). Although 



