The results of the 8,937 line- 

 hours of secondary euid primary 

 trolling have been organized geo- 

 graphically in the same manner as 

 the surface sightings, the two 

 types of trolling being treated 

 separately. These data will be 

 examined for information on the 

 distribution of tuna and will be 

 compared with the surface sightings 

 for consistency between the two 

 measures of abundeoice. The sea- 

 sonal distribution of the troll 

 catches will not be analyzed be- 

 cause of the paucity of data. 



It should be noted particu- 

 larly that trolling, both secondary 

 and primary, fails to sample skip- 

 jack as efficiently as it samples 

 yellowfin. It is commonplace to 

 troll through visible concentra- 

 tions of skipjack without strikes, 

 whereas yellowfin are nearly always 

 taken when there are indications 

 of their presence. In the Hawaiian 

 area Welsh (1950) reported capture 

 of approximately one yellowfin for 

 Figure 8. — Results of longlining between each two skipjack by trolling, a 

 140<%. and 170*^. longitude during 1960-52. ratio in close agreement with POFI 



secondary trolling in the Hawaiian 

 area. But contrasted with this, 

 commercial laiidings by the Hawaiian 

 llvebalt fishery are less than 1 yellowfin for 100 skipjack, showing that trolling 

 takes a far smaller proportion of skipjack than llvebalt fishing does. Paralleling 

 these observations, the results of surface sightings discussed in earlier sections 

 indicate, for all areas, a greater relative abxindance of skipjack than was shown by 

 the troll catches, leading to the conclusion that skipjack are relatively more 

 abundant in most areas than is Indicated by trolling. 



IO°S-0 

 28 DAYS 



Q-5°N 5°-IO°N 

 56 DAYS 25 DAYS 



I0°-20°N 

 9 DAYS 



Island Trolling 



One of the earliest published reports on Island tuna trolling in the central 

 Pacific (Chapman 1946) indicated an abundance of skipjack and yellowfin in the 

 vicinity of the Line and Phoenix Islands. Welsh (1950) has published the results 

 of a general trolling survey of the Hawaiian Islands, indicating that skipjack and 

 little tunny predominated in that area. Bates (1950), reporting on a portion of 

 the POFI trolling in the Line Islands, suggested that the Island populations of 

 yellowfin there were abundsuit enough for commercial trolling. 



There has been no primary trolling by POFI in Hawaiian waters, but data of 

 Welsh (1950) are available for comparison with the various Island areas. He re- 

 ported on 307 hours of trolling with 7 lines, the total catch amounting to 548 

 fish: 46 skipjack, 23 yellowfin, 350 little tunny, 101 dolphin, 8 jacks, and 20 

 wahoo. The survey was made during the period March 1948 to June 1949, and most of 

 the trolling was done around Oahu. In terms of catch per 100 line-hours, the 

 average for all tunas was approximately 19.5. By species it was 1.1 yellowfin, 2.1 

 skipjack, and 16.3 little tunny. These catches are lower than those reported by 

 Tester (1952) (about 27 tuna per 100 line-hours), but his fishing was all done in a 

 particularly productive area off Kaneohe Bay, Oahu. 



Primary trolling by POFI vessels in the Line Islands (table 4) indicated a 

 much higher catch rate than In the Hawaiian Islands, and the catches were dominated 

 by yellowfin. There were 890 line-hours of trolling with a catch of 241 yellowfin, 

 5 skipjack, 171 wahoo, 11 Jacks, 8 rainbow runners, and 24 miscellaneous fish. The 

 average for tuna was 27.6 per 100 line-hours, practically all yellowfin. The sizes 

 of the yellowfin ranged from 13 to 69 pounds. It is probable that larger yellowfin 



12 



