FIGURE l. — General points of collection of spiny dogfish in Puget 

 Sound and the Strait of Georgia. 



Analytical samples were prepared at this 

 laboratory and consisted of the skinned and de- 

 boned edible muscle tissue from both fillets and 

 bellyflaps. Since the bellyflaps are marketed as a 

 separate product, they were removed and 

 analyzed separately. Each sample was ground and 

 thoroughly mixed prior to subsampling for 

 analysis. 



Total mercury was determined by the U.S. Food 

 and Drug Administration's Vanadium Pentoxide 



Method (Munns 1972), which uses a nitric-sulfuric 

 acid digestion with vanadium pentoxide as a 

 catalyst. Final determination was by flameless 

 atomic absorption spectroscopy with results stated 

 in parts per million (ppm) of mercury on a wet- 

 weight basis. All samples were subjected to single 

 analysis, and those exceeding 0.40 ppm were re- 

 peated. Differences between replicates did not ex- 

 ceed 0.05 ppm. A standard fish sample was 

 analyzed routinely as an internal control. 



Results and Discussion 



A total of 141 dogfish (127 females, 14 males) 

 were analyzed for mercury content. Mean mercury 

 levels in specimens from each area (Table 1) were 

 at or above the action level of 0.50 ppm set by the 

 U.S. Food and Drug Administration (FDA) 

 (Schmidt 1974). Specimens taken from the west 

 side of Puget Sound (Port Townsend and Seabeck) 

 contained lower levels of mercury than did those 

 taken from the east side of Puget Sound ( including 

 Blaine). The mercury levels appeared to increase 

 from north to south on each side of the Sound. This 

 phenomenon may be due to the absence of industry 

 at points of collection on the west side of the Sound 

 and an increase of industrial activity from north to 

 south along the east side of the Sound; however, 

 these observations on the effect of catch area may 

 not be representative of the total Puget Sound 

 dogfish population. 



The mean mercury level for the 127 female 

 dogfish fillets was 0.92 ppm, which is almost twice 

 the FDA action level. The mercury level in 91 

 females (729c) exceeded 0.50 ppm and 48 (387c) 

 exceeded 1.0 ppm. Regression analysis showed a 

 positive correlation between mercury content of 



TABLE 1. — Mercury concentration in spiny dogfish from the State of Washington. 



643 



