FISHERY BULLETIN: VOL. 74, NO. 4 



lat. 45° to 50°N in August and September. Accord- 

 ing to Brock (1943), yachts sailing between 

 Hawaii and Oregon during June made albacore 

 catches between lat. 30° and 44°N in waters be- 

 tween long. 154° and 140°W. 



Numerous exploratory fishing and oceano- 

 graphic surveys also have been conducted within a 

 few hundred miles of the coast to obtain informa- 

 tion on distribution, availability, and migration 

 patterns of albacore during early season in waters 

 off the Pacific Northwest (Powell 1950, 1957; Pow- 

 ell and Hildebrand 1950; Powell et al. 1952; 

 Schaefers 1953; Owen 1968; Meehan and Hreha 

 1969; Pearcy and Mueller 1970; and others), and 

 in waters off California (Graham 1959; Clemens 

 1961; Craig and Graham 1961; and others listed in 

 Clemens 1961 and Pinkas 1963). Johnson (1962), 

 Laurs et al. (1976), and others have discussed var- 

 iations in distribution and relative abundance of 

 albacore in waters off North America where the 

 U.S. fishery takes place. These studies have 

 shown: 1 ) the limits of where albacore are found; 2) 

 their general migration patterns; 3) the impor- 

 tance of environmental conditions and changes, 

 notably ocean temperature, in relation to the dis- 

 tribution and relative abundance of albacore; and 

 4) the considerable annual variation in location of 

 available concentrations of albacore. 



In the present study early season albacore sur- 

 veys were planned to encompass a portion of the 

 eastern sector of the Transition Zone during a 

 period prior to the commencement of the near- 

 shore fishery. The primary objectives of these sur- 

 veys were: 



1 1 To investigate the early season distribution 

 and abundance of albacore off the North 

 American Pacific coast. 



2) To investigate the eastward migration path 

 of albacore entering the American west coast 

 fishery. 



3) To determine if migrating albacore are as- 

 sociated with major offshore oceanographic 

 features, particularly the Transition Zone 

 and the ocean fronts that form its bound- 

 aries. 



METHODS 



The general work plan for each offshore survey 

 employed one National Marine Fisheries Service 

 (NMFS) research vessel (Townsend Cromwell in 

 1972 and David Starr Jordan in 1973 and 1974) 



and a group of 5 to 12 commercial albacore fishing 

 vessels on charter to the American Fishermen's 

 Research Foundation ( AFRF). The research vessel 

 and chartered fishing vessels worked coopera- 

 tively to obtain estimates of distribution and rela- 

 tive abundance of albacore in the offshore area and 

 to make concurrent oceanographic measure- 

 ments. The research vessel collected physical, 

 chemical, and biological oceanographic data and 

 conducted supplementary fishing activities. The 

 fishing vessels conducted exploratory fishing, tag- 

 ged fish, and collected surface and subsurface 

 temperature data. The oceanographic findings 

 made on meridional transects were used in direct- 

 ing the exploratory fishing operations, particu- 

 larly at the onset of each survey. In several in- 

 stances, especially in 1973 and 1974, the findings 

 of large numbers offish were used to redirect the 

 research vessel to conduct detailed oceanographic 

 observations in the vicinity. 



Operations Aboard Research Vessels 



Three meridional oceanographic sections were 

 taken along long. 135°, 137°30', and 140°W be- 

 tween lat. 31° and 41°N in 1972 and 1973; in 1974 

 the middle section, portions of the section along 

 long. 135°W, and additional transects were taken 

 (Figure 1). Hydrographic stations were occupied 

 at 25- to 30-n.mi. intervals. Figure 2 shows station 

 positions occupied in 1973; Lynn and Laurs 34 

 gave figures of the station positions for other 

 years. Observations included: 1) salinity- 

 temperature-depth profiles to 500 or 1 ,000 m using 

 an STD; 5 2) Nansen bottle or command rosette 

 sampler 6 bottle casts for collection of water sam- 

 ples for determination of dissolved oxygen, 

 chlorophyll, and salinity; 3) oblique zooplankton 

 net hauls and simultaneous surface hauls with 

 neuston plankton nets; and 4) at night stations, 



3 Lynn, R. J., and R. M. Laurs. 1972. Study of the offshore 

 distribution and availability of albacore and the migration 

 routes followed by albacore tuna into North American waters. In 

 Report of joint National Marine Fisheries Service- American 

 Fishermen's Research Foundation albacore studies conducted 

 during 1972, p. 10-44. (Unpubl. rep.) 



4 Lynn, R. J., and R. M. Laurs. 1973. Further examination of 

 the offshore distribution and availability of albacore and migra- 

 tion routes followed by albacore into North American waters. In 

 Report of joint National Marine Fisheries Service-American 

 Fishermen's Research Foundation albacore studies conducted 

 during 1973, p. 3-35. (Unpubl. rep.) 



s Plessey model 9006 electronic salinity-temperature-depth 

 profiler. Use of a trade name does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



"General Oceanics, Inc. 



796 



