FISHERY BULLETIN: VOL. 75. NO. 4 



Pacific Central 



62°F (16.7°C) 

 62°F 



s=90 m 

 >90 m 



The data were transformed to logarithms in 

 order to standardize between-sample variance. 

 Results of the analysis of variance show that mean 

 catch in the Transition Zone, which was greatest, 

 is significantly different (P = 0.01) from those in 

 other water masses. 



For the 1973 survey, both charter and nonchar- 

 ter vessel catches were available for test. The 

 fronts were assumed fixed for this time frame, as 

 shown in Figure 9b, and catches were assigned to a 

 water mass based upon reported geographic posi- 

 tion. Because no fishing effort was expended in 

 Central waters, except close to the Subtropic front 

 where catches are expected, an analysis of this 

 division could not be included. Both the charter 

 and noncharter vessel data revealed that mean 

 catches were significantly greater (P = 0.01) in the 

 Transition Zone than those in the Subarctic wa- 

 ters. 



The poor development of the boundary fronts 

 between water masses during 1974 precludes a 

 definitive assignment of catch to water mass; 

 therefore, a test of the 1974 data was not consi- 

 dered. 



Catches made by both the charter fishing ves- 

 sels and the research vessel during each of the 

 three surveys demonstrate that albacore are dis- 

 tributed within the Transition Zone and may be 

 absent (or unavailable) or nearly so in water 

 masses to the north and south during this phase of 

 their shoreward migration. Relative abundance is 

 high in offshore areas within the Transition Zone 

 waters and at times close to the oceanic fronts that 

 form the boundaries of Transition Zone waters. 

 Further, when the oceanic fronts are diffuse and 

 widely spread there is likely to be a corresponding 

 spread in the distribution of albacore and a dislo- 

 cation of the centers of high relative abundance. 



MIGRATION PATTERN FROM 

 OFFSHORE TO NEARSHORE WATERS 



We view the general pattern of seasonal migra- 

 tion of albacore into coastal waters where the U.S. 

 fishery traditionally takes place during summer- 

 fall as proceeding in three main stages: First, al- 

 bacore migrate eastward from central North 

 Pacific regions and form centers of high relative 

 abundance within the eastern sector of the Transi- 

 tion Zone waters 600 to 1,000 mi off the coast. This 



development initially occurs in late May and 

 June, a time when seasonal warming has raised 

 the surface layer temperature of these waters to 

 values considered to be within the habitat prefer- 

 ence for albacore. These concentrations offish may 

 persist in offshore waters for several weeks. Next, 

 as nearshore waters warm in ensuing weeks, alba- 

 core migrate toward coastal regions. Fishing ef- 

 forts in the intervening zone usually produce only 

 scattered catches, thus suggesting that during the 

 shoreward migration the behavior of the fish is 

 such that they are not available to fishing gear 

 and/or that albacore may not be concentrated. 

 Then, usually by mid- July, concentrations of high 

 relative abundance are found near the coast, often 

 in the vicinity of oceanic fronts related to coastal 

 upwelling. Although variations may occur in this 

 general pattern, the main features of the migra- 

 tion tend to repeat each year. The stages of shore- 

 ward migration and initial development of the 

 albacore fishery can be seen in the two series of 

 charts showing nominal catch per unit effort for 

 1973 (Figures 5a-e, 6a-e). 



The shoreward migration of albacore from the 

 central North Pacific into coastal waters appears 

 to continue through the summer months. Albacore 

 trolling experiments conducted from U.S. Navy 

 picket vessels operating approximately between 

 long. 130°and 135°W (Flittner 1963, 1964) showed 

 albacore to be available there throughout the 

 summer. Also, two albacore tagged by the 

 Japanese in the western Pacific (near lat. 35°N 

 and long. 171°E) in mid-June 1974 were recovered 

 in the U.S. fishery in September 1974 (Japanese 

 Fisheries Agency 1975). 



Division in Migration Pattern 



In order to examine migration of albacore from 

 offshore to nearshore waters, an albacore tagging 

 program was conducted during each of the offshore 

 surveys. Over 4,500 albacore were tagged and re- 

 leased (Table 1). Recoveries of tagged fish made 

 during the same season as released provide infor- 

 mation on migration of albacore into nearshore 

 waters (Figure lla-c). Most recoveries of tagged 

 fish made in 1972 offish tagged during early sea- 

 son 1972 in waters offshore of long. 130°W were 

 made in central-southern California waters and 

 only a few recoveries were made in Pacific North- 

 west waters (Figure 11a). A similar recovery pat- 

 tern was observed in 1973 (Figure lib). A con- 

 trasting recovery pattern was observed in 1974 



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