Mercury in Swordfish and Other Pelagic 

 Species from the Western Atlantic Ocean 



JAMES S. BECKETT 1 and H. C. FREEMAN 2 

 ABSTRACT 



Total mercury determinations have been carried out on at least one tissue from each of 210 swordfish, 

 40 specimens of 15 other pelagic species, and 235 individuals of 12 species taken from swordfish stomachs. 

 Total mercury levels of swordfish white muscle tissue ranged from 0.05 to 4.90 parts per million (ppm) 

 (mean 1.15 ppm) total mercury. Mercury levels were broadly related to fish size with the larger fish having 

 higher levels but the relationship varied with time and area of capture. Males tended to have higher levels 

 than females. The mercury levels of different tissues (red muscle, liver, kidney, heart, brain, gill, vertebral 

 disc, and stomach) are given. The differences in the levels in certain tissues from fish taken in different areas 

 suggest greater physiological activity of mercury in fish from the southern area. The significance of mercury 

 in swordfish prey species is discussed. 



As a result of the sudden awareness of the pres- 

 ence of mercury in swordfish (Xiphias gladius) and 

 the almost immediate cessation of the fishery in early 

 1971, there were very few specimens with good 

 biological and capture data available for analysis. In 

 order to investigate heavy metal contamination in 

 fishes, the Fisheries Research Board of Canada 

 conducted a series of longlining cruises (Table 1) in 

 the area extending from the southern Caribbean to 

 the Grand Banks. The results of the first five cruises 

 from 1 August 1971 to March 1972 are presented 

 here. 



METHODS 



Regular swordfish longlines were used, the gen- 

 eral gear configuration being Mustad y/ilQ hooks 3 on 

 3-fathom gangings, attached to the mainline at 

 20-fathom intervals. The mainline was held near the 

 surface by buoys, on 5-fathom lines, attached to it 

 every 100 fathoms. The gear was set in the evening 

 and hauled back after dawn. Mackerel (Scomber 

 scombrus) and occasional herring (Clupea haren- 

 gus) were used as bait. 



'Fisheries Research Board of Canada. Biological Station. St. 

 Andrews, New Brunswick, Canada. 



2 Fisheries Research Board of Canada. Halifax Laboratory, 

 Halifax. Nova Scotia, Canada. 



3 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service. NOAA. 



Sex, state of maturity , morphometric and stomach 

 content data were recorded for each swordfish 

 boated. Representative food items were retained for 

 mercury analysis. A number of tissue samples were 

 removed from the swordfish and frozen for future 

 analysis; tissue included: dorsal muscle (posterior), 

 red muscle, abdominal wall muscle, heart, kidney, 

 liver, gill, stomach, and vertebrae. Not all tissues 

 were obtained for each fish. 



Other pelagic species landed were treated in vari- 

 ous ways, some being sampled in detail, as for 

 swordfish, while only dorsal muscle tissue was re- 

 tained from others. Total mercury content was de- 

 termined, in duplicate, on homogenates of each tis- 

 sue by the semiautomated flameless atomic absorp- 

 tion method of Armstrong and Uthe (1971) using a 

 Perkin-Elmer model 403 atomic absorption spec- 

 trophotometer equipped with a Perkin-Elmer model 

 56 recorder. Sampling was performed by a Techni- 

 con Sampler II with a timer cam (30 samples per 

 hour), sample wash ratio of 1:2, and a Technicon 

 proportioning pump. 



RESULTS 



At least one tissue type has been analyzed from 

 210 swordfish (X. gladius), and from 37 individuals 

 of 13 other pelagic species (1 bluefin tuna, Thunnus 

 thynnus; 1 white marlin, Tetrapturus albidus; 1 

 escolar, Lepidocybium flavobrunneum; 3 dolphin, 



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