Accumulated data on the relative vertical distribution of yellowfin, bigeye, and 

 albacore (aee data in Murphy amd Shomura 1953a, b) indicate that yellowfin are usually but not 

 consistently more abundant at the deeper levels in the equatorial Pacific, the best bigeye catches 

 are more regularly associated with the deeper fishing levels, and albacore are clearly caught in 

 greatest abundance on the deepest fishing hooks. This may be a reflection of the general horizon- 

 tal distribution of these three species. Yellowfin appear to be a tropical species; bigeye are also 

 tropical in occurrence but are abundant considerably farther north than the yellowfin (Nakamura 

 1949); surface albacore are abundant in northern waters not inhabited by the yellowfin nor the big- 

 eye. It seems probable that temperature is one of the chief controlling factors in the latitudinal 

 distribution of these species, and very likely it is also responsible, at least in part, for a differ- 

 ence in vertical distribution in the equatorial region, with the species whose distribution extends 

 farther north apparently occupying deeper, colder waters in the tropics. 



Table 17. --Catches of yellowfin on 10 baskets of special 

 gear compared with the catches of the ad- 

 jacent 10 baskets of standard gear, Manning 

 cruise 12 



1/ Identical with standard gear, except that the 



10-fathom float lines were replaced with 30-fathonn 

 lines. 



2/ Gear made up with 2-fathom float lines and with 

 droppers consisting of a 1-foot cotton section, a 

 4-fathonn sekiyama section, and a fathom of wire 

 leader. 



IMPROVEMENT OF LONGLINE GEAR 



The first longlines designed by POFI were essentially modifications of the gear used 

 commercially by Hawaiian and Japanese fishermen. One of the components of this gear is the 



27 



