FISHERY BULLETIN: VOL. 74, NO. 4 



WEIGHT (kg; 

 25 50 



75 



100 



1.50 



E 

 a. 



> 1.00 

 cr 



Z) 



o 



on 



bJ 



0.50 



50 100 150 200 250 



WEIGHT (pounds) 



Figure 5.-Relationship between heads-off eviscerated weight 

 and mercury concentration in the edible muscle tissue of Pacific 

 halibut from British Columbia. 



WEIGHT(kg) 

 50 75 



50 100 150 200 



WEIGHT (pounds) 



250 



Figure 6.-Relationship between heads-off eviscerated weight 

 and mercury concentration in the edible muscle tissue of Pacific 

 halibut from Washington-Oregon. 



Alaska (Figures 2, 3) are so similar as to suggest 

 that the environmental and biological factors that 

 determine the rate and extent of deposition of 

 mercury in the muscle are the same in both areas. 

 In any case, the mean level of mercury and the 

 incidence of fish exceeding the guideline increases, 

 while the size of the fish decreases, from north to 

 south. 



Increasing concentrations of mercury have been 

 noted in other marine animals as one moves south 

 from the Bering Sea. Anas (1974) pointed out that 

 the harbor seal, Phoca vitulina richardi, which is a 

 nonmigratory, inshore carnivore that feeds prin- 

 cipally on fish, provides geographical information 

 on local concentrations of contaminants. The livers 

 of harbor seals taken from the Bering Sea con- 

 tained lower levels of mercury than did those from 

 Washington and Oregon, and those from southern 

 California contained the highest levels. Sablefish, 

 A noplopoma fimbria (Pallas), also shows a similar 

 pattern and will be the subject of another paper in 

 this series. 



These observations suggest that the total mer- 

 cury contamination in the ocean environment 

 (natural plus man-made) increases in a north-to- 

 south direction. Unfortunately, conclusive data to 

 substantiate this hypothesis are not available. 

 Eggerman and Mar (1972), in a review of the 

 research that has been conducted on the various 

 aspects of mercury transport, state that there is a 

 paucity of available data, especially on the 

 biological transport of mercury in marine waters. 



ACKNOWLEDGMENTS 



We thank Lyle Morimoto and Michael Bienn, 

 formerly of the PURC and the SEURC, for assis- 

 tance in mercury analyses; Virginia Stout of the 

 PURC and Murray Amos and Ernest Decorvet of 

 the Northwest Fisheries Center for their help with 

 data processing; and Bernard Skud, Director, 

 IPHC, for his cooperation in this investigation. 



LITERATURE CITED 



Anas, R. E. 



1974. Heavy metals in the northern fur seal, Callorhinus 

 ursinus, and the harbor seal, Phoca vitulina richardi. 

 Fish. Bull., U.S. 72:133-137. 

 Eggerman, T., and B. Mar. 



1972. Mercury in the North Pacific-NORFISH NFOl. Cent. 

 Quant. Sci., Univ. Wash., Seattle, 15 p. 

 Hardman, W. H., and G. M. Southward. 



1965. Sampling the commercial catch and use of calculated 

 lengths in stock composition studies of Pacific halibut. 

 Int. Pac. Halibut Comm. Rep. 37, 32 p. 

 Hatch, W. R., and W. L. Ott. 



1968. Determination of sub-microgram quantities of mer- 

 cury by atomic absorption spectrophotometry. Anal. 

 Chem. 40:2085-2087. 

 International Pacific Halibut Commission. 



1974. Pacific Halibut Fishery Regulations 1974. Int. Pac. 

 Halibut Comm., Seattle, Wash., 5 p. 



788 



