data, further reduced by the tagging of viable 

 albacore, precludes any analysis at this time. 

 Field examination of the gonads failed to reveal 

 sexually mature fish, most of them possessing 

 thin, ribbon-like gonads in the earliest stages 

 of sexual development. 



Tagging of Albacore 



One of the aims of the albacore investi- 

 gation is to determine the relationships of the 

 albacore taken in different parts of the North 

 Pacific, i.e., whether the albacore population 

 of the North Pacific is composed of one or many 

 races or stocks of fish. Recoveries made by 

 the Japanese of albacore tagged off California 

 (Ganssle and Clemens 1953, Blunt 1954) demon- 

 strate ocean-wide migrations. Notable among 

 these is the recovery made on June 23, 1953, 

 by Japanese fishermen about 550 miles south- 

 east of Tokyo (Ganssle and Clemens 1953). 

 This fish had been tagged and released off Los 

 Angeles Harbor, California, on August 4, 1952, 

 324 days before recapture. The albacore had 

 traversed a straight-line distance of 4,900 miles. 



In order to define the relationship of the 

 central Pacific stocks, we have tagged all viable 

 albacore, thus far releasing 79 fish (table 20, 

 Appendix). Tags (Type G) and tagging methods 

 have been essentially the same as those used in 

 California (Wilson 1953). 



OTHER FISHES 

 Other Tunas 



Yellowfin and skipjack were sporadically 

 taken on the longline and trolling gear and then 

 generally south of the albacore, while the single 

 little tunny was caught by trolling indefinitely tro- 

 pical waters. As for the small catch of yellowfin, 

 Nakamura (1951) says that this species ranges as 

 far north as 35 N. latitude and is abundant in 

 the North Pacific during the sumnner, a period 

 for which we do not at present have data. 



Sharks 



The four species of shark comnnonly taken 

 on the longline gear in the North Pacific were the 

 bonito, great blue, thresher, and white-tipped 

 shark. Of the four species, the great blue was 

 by far the most frequently caught and is probably 

 the nnost abundant species of shark in the area. 

 It was taken at 50 of the 52 fishing stations, with 

 the highest day's catch of 40 at station 28 (40 

 12'N. , 174 56'W. ) on cruise 22 of the Manning 

 during October 1954 (tables 17 to 19, Appendix). 



The immediate importance of sharks to 

 the tuna longline fishery lies in the amount of 

 damage they inflict on the tuna catch. In the 

 equatorial area shark-damaged tuna comprise 

 as much as 20 percent of the catch (Murphy and 

 Shomura 1955). In comparison, only 3 of a 

 total of 262 tuna (1. I percent) t2iken on the long- 

 line gear in the North Pacific were shark-bitten, 

 in spite of the heavy population of great blue 

 shark indicated by the longline catches. 



Miscellaneous Species 



In addition to the albacore, the species 

 of tuna taken on longline (tables 11 to 13, Appen- 

 dix) and trolling (table 21, Appendix) gear were 

 the bigeye, yellowfin, skipjack, and little tunny. 

 Of these, the bigeye, which is of commercial 

 innportance in Hawaii and Japan, was by far the 

 most abundant species in the longline catch. 

 Bigeye appeared in the catch at 27 of the 52 

 stations fished, the biggest single catch (30 

 bigeye, or 3.85 fish per 100 hooks) beingmade 

 on Manning cruise 19 at 30°54'N. . 159°54'W. , 

 just south of the biggest albacore catch, which 

 was made at 33 58'N. during the same period. 

 The distributional pattern of the bigeye during 

 the three survey periods (fig. 8) indicates a 

 north-south shift paralleling that of the alba- 

 core; during the fall bigeye were tJiken as far 

 north as 40°N. , but during the winter they were 

 taken only as far north as 34 N, (fig. 8). Bigeye 

 and albacore were taken together at only 6 of the 

 41 stations which yielded tuna, and most of the 

 bigeye were taken farther south than the alba- 

 core, indicating a preference for a more tropi- 

 cal environment. 



Among the miscellaneous species of fish 

 taken on the longline gear were the lancet fish, 

 broadbill swordfish, striped marlin, black mar- 

 lin, short-nosed spearfish, sunfish, dolphin, 

 wahoo, and a newly described species of pelagic 

 sting ray (Ishiyama and Okada 1955). Only the 

 lancet fish, among these, were taken with any 

 regularity (tables 17 to 19, Appendix), and they 

 were found to range widely over the areas fished. 



One pelagic sting ray was captured at 

 station 15 (cruise 19) at 34°41'N. , 154°52'W. 

 and another at station 13 (cruise 23) at 33 50'N., 

 179°44'W. 



Among the troll catches of fish other 

 than tunas (table 22, Appendix) the dolphin was 

 most frequent. It was taken in the southern 

 sectors of the survey areas. 



SUMMARY 



1. Albacore were taken on the longline geEir 

 during all three surveys, with the highest 



18 



