maximum 18.85 ppm for a white shark. The only 

 exceptions were a lancet fish (0.08 ppm) and two 

 basking sharks (0.03 and 0. 14 ppm). The data are too 

 few for any deductions other than that the general 

 tendency is for higher levels to occur in species that 

 eat large fish, although, on this basis, the dusky and 

 scalloped hammerhead sharks may be excessively 

 high. These shark specimens were captured in area 

 A, however, and may be showing elevated levels 

 similar to swordfish from that area. 



CONCLUSIONS 



The decrease in mercury content of dorsal muscle 

 with time for swordfish in the northern part of their 

 range, and the high levels in excretory tissues from 

 fish in the southern warmer areas, suggest that the 

 uptake of mercury may change during the annual 

 migratory cycle. Further data on food species, how- 

 ever, are necessary to confirm whether swordfish 

 are ingesting higher levels of mercury in their prey 

 during the winter when they occur in the Caribbean 

 and southern Gulf Stream, and losing the mercury 

 when they migrate to the north during the summer. 

 The high mercury levels in the kidney and liver tis- 

 sues of one fish taken from area E (Grand Banks), 

 which contrast with the general trend in the northern 

 areas, may indicate heavy feeding on redfish, a 

 species with a high mercury content. 



SUMMARY 



Total mercury contents were determined for at 

 least one tissue from each of 210 swordfish, 40 indi- 

 viduals of 15 other pelagic species and for the body 

 musculature of 235 individuals of 12 prey species. 



Dorsal muscle mercury levels for swordfish of 

 74-247 cm fork length ranged from 0.05 to 4.90 ppm 

 (mean 1.15 ppm). 



Mercury content of the dorsal muscle of swordfish 

 showed a linear relationship with size. 



The mercury content of the dorsal muscle may 

 vary with sex, males having a higher level, possibly 

 being correlated with the older age for a given fish 

 size. 



The mercury content appeared to decrease with 

 time for fish in the northern part of the range. 



Mercury levels in red muscle, liver, kidney, and 

 heart exceeded those of the dorsal musculature, 

 while those in other tissues were less. 



Mercury uptake and/or excretion was higher in the 

 Caribbean and Gulf Stream, south of Cape Hat- 

 teras, than to the north and east. 



Some increase in mercury levels may occur near 

 the Grand Banks where major food items (redfish 

 and squid) were relatively rich in this element. 



The mercury content of other pelagic species ex- 

 amined ranged from 0.03 ppm for a basking shark to 

 18.85 ppm in a white shark. 



ACKNOWLEDGMENTS 



Thanks are due to members of the Fish Contami- 

 nants Division of the Halifax Laboratory for carrying 

 out the mercury analyses, and to the staff at the 

 Biological Station, St. Andrews, especially to those 

 members of the Pelagic Programme who collected 

 much of the material, and to members of the Statisti- 

 cal Group for their assistance in examining the data. 

 Grateful acknowledgement is made of the use of the 

 Canadian Hydrographic vessel Dawson for the 

 Caribbean cruise. 



LITERATURE CITED 



ARMSTRONG, F. A. J., and J. F. UTHE. 



1971. Semiautomated determination of mercury in animal 

 tissue. At. Absorpt. Newsl. 10:101-103. 



BECKETT, J. S. 



1974. Biology of swordfish, Xiphias gladius L. in the 

 Northwest Atlantic Ocean. In Richard S. Shomura and 

 Francis Williams (editors), Proceedings of the Interna- 

 tional Billfish Symposium. Kailua-Kona, Hawaii. 9-12 

 August 1972. Part 2. Review and Contributed Papers. 

 U.S. Dep. Commer. NOAA Tech. Rep. NMFS 

 SSRF-675, p. 103-106. 



SCOTT, W. B., and S. N. TIBBO. 



1974. Food and feeding habits of swordfish (Xiphias gladius 

 Linnaeus) in the Northwest Atlantic Ocean. In Richard 

 S. Shomura and Francis Williams (editors), Proceedings 

 of the International Billfish Symposium. Kailua-Kona. 

 Hawaii, 9-12 August 1972, Part 2. Review and Contrib- 

 uted Papers. U.S. Dep. Commer. NOAA Tech. Rep. 

 NMFS SSRF-675, p. 138-141. 



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