FISHKKY BULLtril.N. VUL. /a. INU. Z 



TRACK *ND OeSERVATONS FOR 2«X Z'UNIT AREA WVESTI6ATI0NS 



START - 



TROLLIMG. DAYLIGHT (6-l/t tti 



— — RU pMVE, night 



FULL SPEED (11-1/2 kO 

 • STO/NISKIN ORNANSENCSCOm) 

 O XBT 



A UICR0NEKT0N.5 XSNET 

 . ZDOPLANKTON.CALCOFI liiiai/2ni 

 " NEUSTON 



D MIWKATER TRAWL (UNIVERSAL 

 TRAWL) 



Figure 2.-Track and observations scheduled for each 2° x 2° 

 unit area during Part II operations. [Dawn trawl haul was 

 eliminated on cruise Jordan 60]. 



1969, in more detail than the previous cruise report 

 by Hida (1970). 



METHODS 



This section deals with methods used on the 1970 

 and 1971 cruises. The Bissett-Berman' Salinity- 

 Temperature-Depth probe (STD) and Sippican 

 expendable bathythermograph (XBT) were used 

 for measuring temperature and salinity. A Niskin 

 12-bottle rosette sampler coupled with the STD 

 was used to collect water samples for salinity and 

 ox>'gen. The STD system had digital (magnetic 

 tape data logger) and analog chart outputs, as did 

 the XBT system (punched paper tape and analog 

 chart). STD /Niskin casts were normally made to 

 500 m and XBT drops to 450 m. Nansen bottle 

 casts, for calibration of the STD system, were 

 made at the start and finish of the Part I transect 

 and at internals during Part II fishing operations. 

 On the Part I transect, STD /Niskin stations for 

 temperature, salinity, and oxygen were made 

 every 6 h, with one or more XBT drops between 

 STD stations. In Part II operations, three STD 

 stations were made at night in each 2° x 2° unit 

 area, and five XBT drops between dawn and dusk 

 on fishing tracks (Figure 2). Processing of the 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



physical oceanographic data was as described by 

 Taft and Miller (1970). Depth of the mixed layer 

 was derived directly from analog charts of XBT 

 and STD systems according to criteria of Owen 

 (1970a). 



Dissolved oxygen content of water samples 

 from the Niskin sampler was determined, and da- 

 ta processed, as indicated by Owen (1970b). 

 Discrete surface samples for chlorophyll a were 

 taken at approximately noon and midnight and 

 processed as described by Owen and Zeitzschel 

 (1970b). 



Zooplankton hauls were made and samples 

 processed by the methods used on EASTROPAC 

 Expedition (Laurs 1970). Oblique hauls from 200 m 

 to surface were made with nets of 50 cm and 1 m 

 mouth diameter in a paired frame. A wire angle of 

 45° was maintained during the haul at a speed 

 about 1.5 to 2 knots. In Part II operations, one 

 daylight haul was made during each of 4 days of 

 fishing in a 2° x 2° unit area (see Figure 2), and 

 three night hauls were made during the 4-day 

 period. No hauls were made near dawn or dusk. 

 Data were expressed in displacement volume in 

 milHHters per 1,000 m\ 



Micronekton was sampled with a net 1.5 m 

 square at the mouth, in oblique hauls from 200 m to 

 surface at a ship speed of 5 knots (Blackburn 1968, 

 1970; Blackburn et al. 1970). During the Part I 

 transect, micronekton hauls were made at 

 approximately 12-h intervals following STD casts, 

 one during daylight and one at night. In Part II 

 operations, day and night hauls were made with 

 the same frequency as for zooplankton (see Figure 

 2). Processing of the samples and estimation of 

 volume of water strained was as discussed by the 

 same authors, and total micronekton was 

 expressed as displacement volume in milliliters 

 per 1,000 m\ A variable and generally large 

 proportion of this micronekton consisted of or- 

 ganisms that skipjack are known or likely to eat 

 (skipjack forage) in the eastern tropical Pacific. 

 The micronekton catches were therefore sorted 

 into forage and nonforage organisms (Blackburn 

 and Laurs 1972). Forage organisms were all crus- 

 taceans, all cephalopods, all epipelagic fish and 

 Vinciguerria. Nonforage organisms were all 

 mesopelagic fish except Vinciguerria and all lep- 

 tocephali. 



The trolling gear used to catch skipjack and 

 other fish was similar to that used in the albacore 

 fishery off the U.S. west coast (Yoshida 1966). 

 Feather jigs were fished with nylon traces and 



384 



