Three types of plankton hauls were made 

 during the four cruises with a 1 -mete r net of 

 656 Nitex (aperture width 0.66 mm.), similar to 

 that which has been described by King and 

 Demond (1953). The purpose of these hauls 

 was to obtain a measure of the standing crop of 

 zooplankton, and to determine the distribution 

 and abundance of tuna larvae. On all the four 

 cruises, a 30 -minute oblique tow to a depth of 

 140 meters was made each night during the 

 runs to and from the Marquesas . During the 

 offshore surveys in the Marquesas, two 0-140 

 meter tows were made nightly. During the off- 

 shore survey conducted during Gilbert cruise 

 35, these nightly tows were paired half -hour 

 tows . 



Longline fishing 



During Gilbert cruise 38 a series of seven 

 longline fishing stations was occupied along 

 longitude 150°W. between latitude 5°N. and 

 1°S. (fig. 1). At each station, 44 baskets of 

 1 1 -hook longline gear were set. The gear used 

 was of POFI design, as described by Mann 

 (1955). Pacific herring ( Clupea pallasii) was 

 used as bait. The longline station data and 

 catch per 100 hooks are presented in table 24; 

 the catch record and sizes of fish in table 25. 



Live -bait fishing 



_ 2. 



Upon completion of the inshore surveys 

 conducted during all four cruises, a 24-hour 

 plankton station was occupied at latitude 

 9°34'S., longitude 139°50'W. The purpose of 

 this station was to obtain data on the diurnal 

 variability of zooplankton and tuna larvae. Two 

 of these stations were occupied during Gilbert 

 cruise 35, and paired 0-140 meter half -hour 

 tows were made every 3 hours. One sta- 

 tion was occupied during Smith cruise 43, and 

 a single 0-140 meter half -hour tow was made 

 every 2 hours. Two stations were occupied 

 during Gilbert cruise 38, and single 0-140 

 meter half -hour tows were made every 2 hours. 

 At the one station occupied during Smith cruise 

 45, 2-net tows were made, a 1 -meter open net 

 towing in the depth range 0-140 meters and a 

 1-meter closing net in the depth range 140-280 

 meters. The latter type of net has been des- 

 cribed by King et al. (1957). These half -hour 

 2-net tows were made every 2 hours. 



During the course of the inshore and off- 

 shore surveys in the Marquesas and in the Tua- 

 motus, fishing trials with live -bait were made 

 on tuna schools encountered. The purpose of 

 these fishing trials was to determine the species 

 and size of tuna in the school, to obtain material 

 for biological studies, to continue the tagging of 

 tunas, and to make observations of biting be- 

 havior. The live -bait fishing techniques used 

 were similar to those of the Hawaiian skipjack 

 fishery, as described by June (1951). The Mar - 

 quesan sardine was used as bait. The station 

 data, catches, and amount of bait used in tuna 

 school fishing trials during the four cruises are 

 presented in tables 26, 27, 28, and 29. The 

 length frequency by sex of samples of yellowfin 

 and skipjack caught during these fishing trials 

 are given in tables 30 through 34, inclusive. 



Baitfish surveys 



Seven half -hour 0-140 meter hauls were 

 nnade at night between the Marquesas and Tahi- 

 ti, during Gilbert cruise 35. The station data 

 amd plankton volumes for hauls made during the 

 four cruises are presented in tables 15, 16, 17, 

 and 18. 



Surface troUin 



£ 



Except when otherwise engaged, the 

 vessels did surface trolling during daylight 

 hours with varying numbers of lines. The 

 catches and related data for the four cruises 

 are presented in tables 20, 21, 22, and 23. The 

 common and scientific names of fish caught are 

 listed in table 19. 



Two procedures were used for conducting 

 baitfish surveys in the Marquesas; daylight 

 visual scouting and night-light fishing. Scouting 

 during the day was done by three or four swim- 

 mers, equipped with faceplates, making a 

 visual sweep of the shallow water in the bays, 

 and noting the schools of bait-sized fish. The 

 procedure and equipment used for capturing 

 bait during the day has been described by June 

 (1951). Night-light fishing was done with the 

 vessels anchored in about 40 -foot depth of water. 

 Marquesan sardines of all sizes were found to 

 be attracted to the diffused light from a flood- 

 light, and the fish were caught alongside the 

 vessel by using a night net of specialized design. 

 The results of visual scouting, day and night- 

 light fishing for the four cruises are given in 

 tables 35 through 38, inclusive. The length fre- 

 quency by sex of Marquesan sardine samples 

 is presented in tables 39 through 42, inclusive. 



