METHODS OF COLLECTION 

 AND ANALYSIS OF DATA 



The nature and extent of our observations 

 varied during 1954. On the two POFI experi- 

 mental cruises observations on the catch and 

 fishing operations were obtained by trained per- 

 sonnel. The commercial vessels carried only 

 a single government observer or none at all; in 

 the latter case the vessel captain recorded in- 

 formation in a log provided by POFI (fig. 1). 



Koont ^lnd force 



::ind dlreotlo:. 



TI1S OP SETTING AND HAULING 



At the first day's fishing sketch one basket or reel of 

 each type of goar used. Secord any modifications of fear 

 on this form. 



Balti Kindt b) 

 Bait hooking 



Bait oonditloi 



11/3/54 



Figure 1. --Pacific Oceanic Fishery 

 Investigations' Longline Fishing Log. 



Also, certain facilities and equipment, such as 

 a bathythermograph winch, were not available 

 on the commercial boats. As a result, the in- 

 formation from this source was not as complete 

 as that from the POFI research vessels. 



There were differences in the gear used 

 from cruise to cruise both in respect to design 

 and materials. To some extent these variations 

 affected the catch rates. The longline gear with 

 fabric mainline had as few as 6 and as many as 

 15 droppers per basket. Shomura and Murphy 

 (1955) found that catch rates of yellowfin tuna 

 in terms of fish per 100 hooks taken on gear 

 with 11 droppers per basket should be multiplied 

 by 1.52 to make them equivalent to catch rates 

 on gear with 6 droppers per basket. Catch rates 



are given in terms of 11-hook gear, except in 

 our comparison of American and Japanese fish- 

 ing results at different longitudes. In this case 

 rates of American vessels have been converted 

 to 6 -hook equivalents to make them comparable 

 to the Japanese catch rates. The length of the 

 droppers on 6-hook gear used on cruise 15 of 

 the Charles H. Gilbert was 10 fathoms as com- 

 pared with the usual 3 fathoms, but the differ- 

 ence is not believed to have markedly altered 

 the catch rates, for the efficiency of long and 

 short droppers has been compared and no sig- 

 nificant difference demonstrated (Shomura and 

 Murphy 1955). On this same cruise both 1- and 

 10-fathom float lines were used on some stations 

 (tables 6 and 7 - Appendix), but previous experi- 

 ments have indicated no significant difference in 

 yellowfin catch rates resulting from the use of 

 different length float lines (Murphy and Shomura 

 1953b). 



Longline gear with the mainline of wire rope 

 was used on two commercial ventures of the 

 Commonwealth (cruises 1 and 2), Oceanic and 

 Brothers (cruises land2), and one experimental 

 fishing cruise of the John R. Manning (cruise 20) . 

 The steel gear was introduced to increase the 

 efficiency of operation of longline fishing. Steel 

 mainline can be spooled on a reel rather than 

 coiled in baskets, which results in a very con- 

 siderable saving of labor. There is some 



1 1 1 \ 



-o COTTON GEAR 

 * STEEL GEAR 



100 1 1 10 120 130 



sm/SuT 



140 



150 160 



MEDIUM 

 LENGTH(CM) 



LARGE 



Figure 2. --Comparison of steel and cotton gear 

 yellowfin catch rates by size groups, John R. 

 Manning cruise 20. 



