MURPHY and SHOMURA: PRE-EXPLOITATION ABUNDANCE OF TUNAS 



175* E 180* 



175* 



170* 



165' 



160* 



155' 



150' 



145* 



140* 



25* 



N 



2cr 



1 5' 

 10* 



^ 



I35» 



130° 



125' 120' W II5« 



25» 



N 



20* 



15* 



PHOENIX ISLANDS 



CANTON I 



McKEAN I 

 GARDNER I 



ENDERBURY I 



BERNIE I  *, 



PHOEIilX I 

 SYDNEY I 



5*S- 



170" W 



HAWAI IAN 

 ISLANDS 



-^ 



I 

 — • .-• ,-i- 



KINGMAN RF 

 >  .PALMYRA I 



5*N- 



LINE 

 ISLANDS 



WASHINGTON I- • 



FANNING I. 

 t 



CHRISTMAS I • 



I60» W 



i-r UIN^^-Os-^— ;.— ^? 



i / ISLANDS V^; .f -v. .» 



-PHOENIX 

 ISLANDS 



m 



^ Pit • '*•*• 



J • * 



MARQUESAS ISLANDS 



•I* 

 •1 



175* 



E 180* 175* 



170* 165* 



I60* 



155* 



150* 



145* 



140* 



135* 



130* 



125* 120' W 115° 



Figure 1. — Locations of longline stations. The circles show the location of an island or group of islands. 



BRANCH LINE 



9/0 HOOK 



Figure 2. — Schematic diagram of tuna longline gear. 



Trolling 



Systematic trolling (Figure 3) provided an- 

 other useful measure of tuna abundance. Gen- 

 erally when the vessels were underway (7-9 

 knots) two 45.7-m lines were trolled astern. A 

 variety of tuna lures was used (Murphy and 

 Ikehara, 1955). Occasionally near the islands, 

 the "standard trolling" was modified by reducing 

 vessel speed and trailing more than two lures. 

 The catches from this type of fishing are con- 

 sidered separately from those of standard trol- 

 ling. 



Surface Sighting 



As a further measure of tuna abundances, the 

 abundance of surface schools of fish, bird flocks, 

 and other signs of life was estimated by con- 

 sistently maintaining a bridge log of sightings 

 (Figure 3). A log of these observations was 

 kept by the wheel watch under the supervision 

 of the scientists on board (Murphy and Ikehara, 

 1955). These records provided a unique body 

 of quantitative information on the bird and fish 

 life in the central Pacific. 



SPECIES OF FISH 



Though the tunas are the most abundant and 

 commercially most valuable of the large pelagic 

 fishes in the central Pacific, a number of other 

 species occupy prominent positions in the biota. 

 The following list of species is largely based on 

 longline catches, but it includes those likely to 

 be captured by trolling or to be seen at the 

 surface. The vernacular names listed below are 

 used throughout the rest of this report. 



877 



