NOTES 



THE SOURCE OF COBALT-60 AND 



MIGRATIONS OF ALBACORE OFF 



THE WEST COAST OF NORTH AMERICA 



Cobalt is an integral part of the vitamin B 12 com- 

 plex and an important cofactor in enzyme systems 

 (Lowman et al. 1971; Reichle et al. 1970). It is, 

 therefore, an element whose cycle in oceanic 

 ecosystems is of interest. The artificial radionuc- 

 lide cobalt-60 ( 60 Co) has been observed in the liv- 

 ers of albacore, (Thunnus alalunga Bonnaterre) 

 collected off the west coast of North America, 

 Washington to Baja California (Pearcy and Oster- 

 berg 1968; Hodge et al. 1973). 



The albacore is a commercially important mi- 

 gratory species of tuna which normally inhabits 

 the epipelagic subtropical and transitional waters 

 of the Pacific, Atlantic, and Indian oceans. In the 

 North Pacific, albacore may undertake trans- 

 pacific migrations between Japan and the west 

 coast of America (Clemens 1961; Otsu and Uchida 

 1963; Clemens and Craig 1965). 



While single-pass nuclear reactors were oper- 

 ated at Hanford, Wash., the Columbia River was 

 an important source of artificial radionuclides in 

 the Pacific Ocean off Oregon and Washington. 

 Some radionuclides, formed by neutron activation 

 of impurities in river water used to cool the reac- 

 tors, were transported via the Columbia out into 

 the ocean and were detectable in the plume water 

 far at sea (Osterberg et al. 1965). Cobalt-60 was 

 among the radionuclides carried by the Columbia 

 River effluent (Gross and Nelson 1966). Fallout 

 from nuclear detonations, however, was another 

 source of 60 Co (Lowman and Ting 1973; Hodge et 

 al. 1973). Which of these sources was more sig- 



nificant in contaminating tuna is not known. We 

 shall attempt to use the temporal and geographi- 

 cal variations in 60 Co content of albacore livers to 

 estimate the relative importance of the two 

 sources and to provide information on migrations 

 of albacore. 



Methods 



During the period June-October of 1963 

 through 1969, over 200 albacore livers were re- 

 moved from fish (520-850 mm fork length, x = 

 640 mm) collected on surface jigs and preserved 

 aboard ships either by freezing or with Formalin. 1 

 In the laboratory, livers were weighed, dried, 

 ashed (500° to 570°C), ground, and packed into 

 15-cm 3 plastic counting tubes for radioanalysis. 

 Samples were counted for 100 min using a 12.7- 

 cm 2 Nal (Tl) crystal detector with a 512 channel 

 pulse-height analyzer. See Pearcy and Osterberg 

 (1968) for additional details on collection and 

 analysis. Results are expressed in picocuries per 

 gram wet weight to be compatible with other pub- 

 lished results on cobalt in tuna livers. 



Results and Discussion 



Concentrations of 60 Co in the livers of albacore 

 caught in three general regions along the west 

 coast of North America are shown in Figure 1 for 

 1964. Of all the years, 1963-69, this year provided 

 the most data for inter-regional and temporal 

 comparisons. Two general trends are evident: 



■Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



~ I0 r 







Q. 



O 

 V 



o 



CD 



1 



001 



N. Ore. a Wash. 





S. Ore. 



_L 



4 



_i_ 



I 



A 



S. & Baja Calif. 



J A S 

 MONTHS 



FIGURE 1 — Cobalt-60 concentrations 

 (dots = actual observations, open 

 triangles = x values) from livers of al- 

 bacore captured off three west coast re- 

 gions during June-October 1964. 



867 



