Table 1,--Line Islands fishing surveys, January 1955 to February 1956 



— Not discussed; catch rates in Appendix, 



DESCRIPTION AND OPERATION OF GEAR 



Trolling 



The trolling gear consisted of two 

 booms, one mounted on either side of the 

 vessel, each carrying two or more (usually 

 three) cotton trolling lines. The lures were 

 the common feather jigs (lead and plastic 

 heads), plastic lures, bone type jigs, plugs, 

 and spoons. A complete description of the 

 method and equipment is given by Bates (1950). 



Surface trolling was done close to the 

 several islands of the Line Islands group, 

 usually within 3 miles of the reefs. Although 

 the islands were often circled during the troll- 

 ing operations, the majority of the fishing was 

 carried out at the boundaries of the eddies and 

 in the lees of the islands, for yellowfin appeared 

 to be more abundant there than on the windward 

 sides. Bates (1950) also found this to be true. 



Longlining 



The other method employed to sample 

 the abundance of yellowfin was longlining. 

 The type of longline gear used in 1955-56 has 

 been described in detail by Mann (1955). Briefly, 

 each basket was composed of a 210-fmi. main- 

 line with 10-fm. float lines; the 11 branch lines 

 or droppers were 3 fm. in length and were spaced 

 at 15-fm. intervzils. 



For comparison with previous years 

 when 6-hook gear was standard, a conversion 

 factor must be applied to the 1 1 -hook catch 

 rates. Shomura and Murphy (1955) have shown 

 that the catch rates of yellowfin on gear with 



1 1 hooks per basket are consistently lower than 

 on 6-hook gear and should be multiplied by 1. 52 

 to make them equivalent. 



Studies on the Improvement of longline 

 gear for greater operational efficiency continued 

 along two lines. First, an improved method of 

 handling f ab r i c gear to replace the present 

 method of storing the gear in individual units 

 or baskets was tested. This innovation consists 

 of coiling the entire mainline into a large r e - 

 volving tub (frontispiece). Float lines and 

 dropper lines are attached when the gear is set 

 and removed when it is retrieved. While the 

 time required to handle gear by this new method 

 is about the same as for the conventional Japa- 

 nese method, less manpower is needed. 



The second attempt at improvement 

 involved the use of a mainline constructed of 

 small-diameter wire rope. The results of its 

 use on cruise 24 of the John R. Manning were 

 not particularly encouraging because of opera- 

 tional difficulties. There was, however, no 

 indication of a significantly lower catch rate on 

 steel gear than on fabric gear (fig. 1), as had 

 been observed in the past. Comparison of catch 

 rates by these two gear types during 1954 showed 

 that the steel gear caught fewer fish, partly 

 because of the loss of larger fish due to the low 

 resilience of the steel mainline gear (Iversen 

 and Yoshida 195 6). The size of yellowfin caught 

 on both gear types was sinnilar during 1955 

 (fig. 2), Despite the similarity in the 1955 

 catch rates for the two gear types, it does not 

 seem that steel gear has sufficient superior 

 operational characteristics to warrant continued 

 experimentation. This conclusion is based on 

 an unpublished analysis by POFI scientists in 

 which cost, time, and labor were considered. 



