MERCURY IN FISH AND SHELLFISH OF THE NORTHEAST PACIFIC. 

 I. PACIFIC HALIBUT, HIPPOGLOSSUS STENOLEPIS 



Alice S. Hall/ Fuad M. Teeny,i Laura G. Lewis/ William H. Hardman,^ and Erich J. Gauglitz, Jr.' 



ABSTRACT 



A total of 1,227 Pacific halibut, Hippoglossus stenolepis, were analyzed for mercury content in the edible 

 muscle tissue. These fish were obtained from five geographical areas within the species range: the 

 Bering Sea, Gulf of Alaska, southeast Alaska, British Columbia, and Washington-Oregon. Mercury was 

 found to be uniformly distributed from nape to tail in the edible muscle tissue. Within each 

 geographical area the mercury concentration increased as the size of the fish increased. The mercury 

 concentration also increased in fish of the same size from the northern to the southern part of the 

 species range. 



In the past few years, numerous investigators 

 have examined the distribution and levels of 

 mercury in food, including aquatic food animals, 

 because of the potential health hazards involved. 

 The U.S. Food and Drug Administration estab- 

 lished an administrative guideline of 0.50 ppm 

 mercury in fish and shellfish in 1969. Since that 

 time, the guideline has been the subject of several 

 reviews and recently has been proposed as a 

 formal action level (Schmidt 1974). 



Since 1970, the Pacific Utilization Research 

 Center (PURC) and the Southeast Utilization 

 Research Center (SEURC) at College Park, Md., 

 have been conducting extensive studies of fish and 

 shellfish taken from marine and inland waters of 

 the United States to determine the extent to 

 which mercury exceeds the guideline in our aquat- 

 ic resources. This paper reports our findings on 

 mercury in the edible tissue of the Pacific halibut, 

 Hippoglossus stenolepis Schmidt. 



EXPERIMENTAL PROCEDURE 

 AND METHODS 



Halibut were obtained from commercial fishing 

 vessels, fish processing companies, and research 

 vessels of the International Pacific Halibut Com- 

 mission (IPHC). Data were obtained on area and 

 date of catch, and weight or length of each fish 



'Pacific Utilization Research Center, National Marine Fish- 

 eries Service, NOAA, 2725 Montlake Blvd. East, Seattle, WA 

 98112. 



^International Pacific Halibut Commission, P.O. Box 5009, 

 University Station, Seattle, WA 98105. 



analyzed. Data were also obtained on age and sex 

 when possible. 



The five areas of catch were: Washington- 

 Oregon, British Columbia, southeast Alaska, Gulf 

 of Alaska, and the Bering Sea (Figure 1). Com- 

 mercial halibut are eviscerated at sea, landed as a 

 heads-on eviscerated product, and then beheaded 

 for marketing as fresh or frozen fish. Weights 

 reported here are in pounds for heads-off eviscer- 

 ated fish because this is the standard practice of 

 the halibut industry. For convenience of some 

 readers who do not normally use our measurement 

 system, approximate metric equivalents in kilo- 

 grams are given in the tables and figures. When 

 actual weights were impractical to obtain, the 

 lengths of the heads-on fish were used, and heads- 

 off eviscerated weights were estimated using 

 length-weight conversion tables of the IPHC. Age 

 was determined, as described by Hardman and 

 Southward (1965), from otoliths collected at the 

 landing site when circumstances permitted and on 

 all halibut taken by IPHC research vessels. 



Before setting up sampling procedures, exper- 

 iments were carried out to determine the unifor- 

 mity of distribution of mercury in the muscle of 

 individual fish. No significant differences in con- 

 centration of mercury (deviation did not exceed 

 ± 0.03 ppm) were noted in muscle tissue taken from 

 nape, midbody, or tail sections. 



Analytical samples consisted of skinned and 

 deboned edible muscle tissue that was normally 

 taken from the nape section just behind the head. 

 Some samples, however, were in the form of steaks 

 and a few consisted of the entire fillets of small 

 fish. Portions, usually about 400 g, taken from the 



Manuscript accepted March 1976. 

 FISHERY BULLETIN: VOL. 74, NO. 4, 1976. 



783 



