Live -bait fishin 



£ 



Fishing trials with live -bait were made 

 from the Gilbert on 103 surface tuna schools in 

 the Marquesas and Tuamotus. The Marquesan 

 sardine and goatfish were used as bait. Of the 

 total catch of 4, 838 skipjack and 5Z yellowfin, 

 797 skipjack and 10 yellowfin were marked with 

 the POFl type D-2 tag and released, all in the 

 Marquesas area. The station data, catches, 

 and bait used are listed in table 20. The live - 

 bait fishing techniques for surface schools were 

 similar to the techniques of the Hawaiian skip- 

 jack fishery, as described by June (1951). 



Baitfish surveys 



Two procedures were used for conduct- 

 ing baitfish surveys in the Marquesas; day 

 visual scouting and night-light fishing. Visual 

 scouting during the day was done by three 

 or four swimmers, equipped with faceplates, 

 making a "sweep" of the shallow water in the 

 bays and noting the schools of bait-sized fish. 

 Night-light fishing was done with the Gilbert 

 anchored in about 40 feet of water. Marquesan 

 sardines of all sizes were attracted to the dif- 

 fused light from a floodlight, and the fish were 

 caught alongside the vessel using a "night net" 

 of specialized design. Results of visual scout- 

 ing, day fishing, and night-light fishing are 

 presented in table 21. 



Biological observations 



Routinely, the fork length of represent- 

 ative samples of the tunas and bait species was 

 taken and recorded. Station data and length 

 frequency summaries of catches made from 

 both the Gilbert and Manning are presented in 

 tables 22 through 28, inclusive. 



During daylight hours on all three 

 vessels, a watch was kept for birds, tuna 

 schools, and aquatic nnammals. Summaries of 

 these observations are presented in tables 29 

 through 32, inclusive. 



Field party personnel 



Hugh M. Smith 



Barnes Collinson, Master 



Everet C. Jones, Field Party Chief 



Thomas S. Hida, Fishery Aid 



John W. Van Landingham , Physical 



Science Aid (Chemist) 

 Robert T. B. Iversen, Physical 



Science Aid 



Charles H. Gilbert 



William T. Tanaka, Master 



Robert C. Wilson, Field Party Chief 



Heeny S. H. Yuen, Fishery Research 



Biologist 

 Garth I. Murphy, Fishery Research 

 Biologist (first half of cruise) 



John R. Manning 



Fred E. Barnett, Master 



Wilvan G. Van Campen, Field Party 



Chief 

 Howard O. Yoshida, Fishery Research 

 Biologist 



LABORATORY PROCEDURES 



Ocaanographic data 



The salinity samples were analyzed by 

 the Fajans modification of the Mohr method 

 (Van Landinghann 1957). The inorganic phos- 

 phate samples were analyzed by the hydrazine 

 sulphate modification of Denige's method (King 

 et al. 1957). 



The oceanographic station data werepro- 

 cessed by the use of techniques described by 

 Montgomery (1954), Montgomery and Wooster 

 (1954), Stroup (1954), and King et al. (1957). 

 The curves for each station are included in 

 table 1. 



Rate of carbon fixation 



A detailed description of laboratory pro- 

 cedures for the determination of the amount of 

 0^4 photosynthetically fixed per unit of time 

 and associated calculations has been given by 

 King et al. (1957). The counting, using a 

 Tracerlab SC16 windowless gas flow counter 

 and a Tracerlab 1000 Scaler or a Nuclear Chi- 

 cago 16 lA Scaler, was done at the University of 

 Hawaii, Department of Botany. The results of 

 these measurements are given in table 11. 



Zooplankton 



The displacement volumes of the plankton 

 collected on oblique and surface tows made 

 from the Smith and the surface tows made from 

 the Gilbert are given in tables 12 and 13. These 

 volumes were determined after removing all 

 fish eggs and larvae, as well as all "jellies" 

 greater than 2 cm. in length. The details of 

 the method are described by Hida and King 

 (1955). 



