LAURS and LYNN: SEASONAL MIGRATION OF THUNNUS ALALUNGA 



150° 145° 140° 135° 130 



48' 



i — i — r 



115° 

 48° 



45" 



40 c 



35 c 



30 c 



RESEARCH VESSEL 

 CRUISE TRACKS 

 MAY- JULY 



1972 

 1973 

 1974 



.-- f SAN DICGO 



.^-J I  



J I L 



J L 



J 



150° 



145° 140° 135° 130° 125° 120° 



FIGURE 1. — Albacore research vessel cruise tracks for the 1972-74 offshore research surveys. 



115° 



oblique midwater trawl hauls using an Isaacs- 

 Kidd Midwater Trawl. Also, surface temperature, 

 salinity, and chlorophyll were recorded continu- 

 ously while underway. 



Generally, 10 jiglines (five on Townsend Crom- 

 well cruise in 1972) were trolled for albacore on 

 transects between oceanographic stations during 

 daylight. In some regions that were not covered by 

 fishing vessels, trolling was carried on by the re- 

 search vessel exclusively throughout daylight. On 

 such fishing days, three or four expendable 

 bathythermograph (XBT) drops were made in ad- 

 dition to continuous monitoring of surface temp- 

 erature, salinity, and chlorophyll. 



Operations Aboard Fishing Vessels 



The AFRF charter vessels which took part in the 

 offshore surveys were jigboats, except for two 

 baitboats in 1973 which were outfitted to conduct 



either live-bait fishing or jig fishing. Twelve 

 fishing vessels participated in the operations in 

 1972 and 1973 and five in 1974. 



The fishing vessels sailed in groups of four from 

 San Diego, Calif., and Astoria, Oreg., at 15- to 

 20-day intervals during 1972 and 1973, and all 

 vessels sailed together from San Diego in 1974. 

 The vessels usually worked in pairs. A schematic 

 diagram of the cruise tracks for the 1972-74 

 offshore surveys is shown in Figure 3. Detailed 

 cruise tracks showing daily positions and loca- 

 tions of XBT stations for each fishing vessel or pair 

 of fishing vessels by 10-day period are given in 

 Lynn and Laurs 7 (see footnotes 3 and 4). 



7 Lynn, R. J., and R. M. Laurs. 1974. Cooperative NMFS-AFRF 

 early season offshore studies conducted during 197 4. In Report of 

 joint National Marine Fisheries Service- American Fishermen's 

 Research Foundation albacore studies conducted during 1974, p. 

 3-18. Southwest Fish. Cent. Admin. Rep. LJ-74-47 



797 



