LAURS and LYNN: SEASONAL MIGRATION OF THUNNUS ALALVNGA 



area, one in the north off Oregon and the other in 

 the south off southern California." 



Results of studies on the artificial radionuclide 

 60 Co in albacore provide additional evidence that 

 the "northern" and "southern" groups of fish are 

 independent. Krygier and Pearcy (1977) found 

 that the peak activity levels of 60 Co in albacore off 

 Oregon occurred a year earlier than the peak ac- 

 tivity levels seen by Hodge et al. (1973) off south- 

 ern California. According to Krygier and Pearcy, 

 the heaviest fallout input of 60 Co into the North 

 Pacific occurred at about lat. 40°N. They specu- 

 lated that due to circulation in the North Pacific, 

 albacore which were associated with waters north 

 of lat. 35°N could have experienced high levels of 

 60 Co up to a year before the tuna associated with 

 waters to the south. They concluded that, "Circu- 

 lation in the North Pacific and the latitudinal dif- 

 ferences in the location of the two portions of the 

 albacore population [as proposed by Laurs and 

 Lynn in this paper] appear to be a plausible expla- 

 nation for the difference of 1 yr in activity peaks 

 between albacore caught off Oregon by us and 

 those off southern and Baja California by Hodge et 

 al. (1973)." Thus, strong evidence from several 

 independent sources points toward two separate 

 groups of albacore following separate migration 

 paths. 



ACKNOWLEDGMENTS 



We thank the American Fishermen's Research 

 Foundation for their farsighted interest and their 

 support for albacore and oceanographic research 

 (particularly, in this regard, Robert Insinger and 

 John Bowland). We owe a debt of gratitude to the 

 captains and crews of the RV Townsend Cromwell 

 and David Starr Jordan, and the chartered fishing 

 vessels, and to the staff of the Albacore Fishery 

 Investigations whose loyal support and perserver- 

 ance made this work possible. 



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