SEASONAL MIGRATION OF NORTH PACIFIC ALBACORE, 



THUNNUS ALALUNGA, INTO NORTH AMERICAN COASTAL WATERS: 



DISTRIBUTION, RELATIVE ABUNDANCE, AND ASSOCIATION 



WITH TRANSITION ZONE WATERS 



R. Michael Laursand Ronald J. Lynn 1 



ABSTRACT 



In the spring months of 1972-74, fishery-oceanography surveys were conducted in the eastern North 

 Pacific which combined intensive oceanographic sampling by research vessels with concurrent fishing 

 effort for albacore by chartered commercial fishing vessels. The catches demonstrate an association of 

 albacore distribution with the Transition Zone and its boundaries. The relative abundance of albacore 

 was found to be high in the eastern sector of the Transition Zone or a period just prior to their movement 

 across the California Current and into the traditional nearshore fishing grounds. These centers of high 

 relative abundance of albacore are sometimes sufficient to support commercial fishing earlier and 

 farther offshore than the traditional fishing season. Variations in the pattern of migration occur in 

 apparent response to variations in the character and development of the Transition Zone and its frontal 

 structure. Analyses of albacore tagging and size frequency data provide evidence that the shoreward- 

 migrating albacore of the Pacific Northwest and California are independent groups. 



The North Pacific albacore, Thunnus alalunga 

 (Bonnaterre), is a wide-ranging species which 

 spawns in the central subtropical Pacific, performs 

 transpacific migrations, and supports important 

 commercial fisheries in the western, central, and 

 eastern North Pacific. That marked variations in 

 distribution and relative abundance of albacore 

 occur in the eastern North Pacific is indicated by 

 major latitudinal shifts in the location of the U.S. 

 fishery off the west coast of North America (Laurs 

 et al. 1976). In order to evaluate factors which may 

 affect variations in distribution, relative abun- 

 dance, and migration patterns of albacore in the 

 eastern North Pacific, and to improve our under- 

 standing of the underlying factors affecting the 

 onset and subsequent development of the fishery, 

 early season surveys were conducted in offshore 

 waters of the North American Pacific coast in 

 1 972-74. 2 These surveys found that relative abun- 

 dance of albacore was high in the vicinity of 

 oceanic fronts of the Transition Zone waters in the 

 eastern North Pacific. Survey results also provide 



'Southwest Fisheries Center, National Marine Fisheries Ser- 

 vice, NOAA, P.O. Box 271, La Jolla, CA 92038. 



2 These surveys were carried on cooperatively by the National 

 Marine Fisheries Service, Southwest Fisheries Center La Jolla 

 Laboratory, and the U.S. albacore fishing industry through the 

 American Fishermen's Research Foundation. 



Manuscript accepted February 1977. 

 FISHERY BULLETIN: VOL. 75. NO. 4. 1977 



the basis for a hypothesis concerning migration of 

 albacore into coastal waters off the west coast of 

 North America. During these surveys albacore 

 were taken in commercial concentrations farther 

 offshore than traditionally, and several weeks ear- 

 lier than the fishing season which usually com- 

 mences in mid-July. 



BACKGROUND INFORMATION 



Numerous exploratory albacore fishing and al- 

 bacore oceanographic surveys have been con- 

 ducted in the central and eastern North Pacific. 

 From surveys conducted during the 1950's, scien- 

 tists described seasonal variations in distribution 

 of albacore in the central and parts of the eastern 

 Pacific, and demonstrated the association of alba- 

 core with Transition Zone waters in the central 

 North Pacific (Shomura and Otsu 1956; Graham 

 1957; McGary et al. 1961 >. Flittner <1963, 1964) 

 reported on albacore trolling experiments con- 

 ducted from U.S. Navy picket vessels operating 

 approximately along long. 130° to 135°W, and pre- 

 sented a schematic model of albacore movement 

 off the Pacific coast (Flittner 1963). Neave and 

 Hanavan 1 1960) showed that the northern limit of 

 albacore catches made during high-seas salmon 

 gillnetting studies conducted between long. 125° 

 and 175°W was about lat. 45 c to 47°N in July and 



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