Surface samples for determination of sa- 

 linity and inorganic phosphate were taken at most 

 of the off -station BT casts. Surface salinity 

 samples were taken by the Hugh M. Smith at ap- 

 proximately 30 -mile intervals fronn Honolulu to 

 the survey area, from the survey area to Hono- 

 lulu, and surface salinity and inorganic phosphate 

 samples were taken at each off -station BT cast 

 in the survey area. Salinity and inorganic phos- 

 phate samples were taken by the John R. Manning 

 at approximately 60 -mile intervals from Hono- 

 lulu to Astoria and at approximately 30 -mile in- 

 tervals from Astoria to 30°N. latitude (see fig. 

 2 for her track) . 



Bathythermograph Observations 



A 900 -ft. BT cast was made from the Hugh 

 M. Smith , before and after each Nansen bottle 

 cast. When surface temperatures were 66 °F. 

 or less, BT casts were made at intervals of not 

 more than 15 miles, when abrupt surface tem- 

 perature changes were indicated on the record- 

 ing thermograph, and each time albacore were 

 landed if one hour had elapsed since the previous 

 lowering. At surface temperatures greater than 

 66 "F, two BT's were taken between oceanogra- 

 phic stations . The positions of sind observations 

 made at the Snnith's BT casts are given in table 3. 



From the John R. Manning , 900 -ft. BT 

 casts were made at approximately 30 -mile in- 

 tervals and also before and after each gill-net 

 station. From Astoria, Oregon, to about 30 °N. 

 latitude, 450 -ft. BT casts were also made at 

 0300 zone time on the nights when the gill nets 

 were set. The positions of and the observations 

 made at the Manning's BT casts are given in 

 table 4. 



The BT slides were processed by the United 

 States Navy Hydrographic Office cind the data 

 were used to construct the temperature cross 

 sections along the vessel tracks; Hugh M. Smith 

 ■ infigures 4to 16 ajid John R. Manning in figures 

 17 to 27. The portion of the tracks included in 

 each of the cross sections is indicated by the 

 letters on the vessel tracks (figs. 1 and 2). 



Meteorological Observations 



Synoptic weather observations as outlined 

 in the United States Weather Bureau Circular M 

 (1956) were made aboard both our vessels at 

 0000, 0600, 1200, and 1800 GOT jind transmitted 

 to the United States Weather Bureau at Honolulu 

 or San Francisco, whenever radio conditions per - 

 mitted. A summary of these observations as 

 recorded on United States Weather Bureau Form 

 12 lOF are listed in tables 5 (Smith) ajid 6 (Manning). 



Subsurface Illumination and 

 Water Color Measurements 



Measurements of the percentage of sub- 

 surface illumination relative to that at the sea 

 surface were made from the John R. Manning 

 at 75 stations. Measurements were made not 

 earlier than two hours after sunrise and not later 

 than two hours before sunset. A Schueler photo- 

 meter, which has been described by Callaway 

 (1957), was used. The response curve of the 

 photometer matched the standard curve of the 

 International Commission on Illumination which 

 has a spectral range of 430 to 700 nnillimicrons 

 and a peaJc sensitivity at 550 millimicrons!.'. 

 The total incident light was estimated in foot 

 candles with a standard camera exposure meter . 

 Because the cable to the sea cell broke repeat- 

 edly, the 1 -percent level of illumination was 

 measured only occasionally. Some values at 

 the 50-percent and 10 -percent levels are also 

 open to question because the shadow of the ship's 

 hull and rigging interfered. The results are 

 given in table 7. 



Secchi disc and Forel water color obser- 

 vations were made from both the Manning and 

 Smith. The Secchi disc observations were made 

 in the manner described in the United States Navy 

 Hydrographic Office Publication 6 07 (1955). 

 Water color as it appeared according to Forel's 

 scale against the Secchi disc background was also 

 made at each lowering. Aboard the Smith these 

 observations were made at 0800 zone time while 

 operating outside the NEPAS area. Within the 

 area they were made daily at 1300 zone time and 

 after each albacore school had been worked when 

 light and sea conditions were suitable. The 

 Smith's results have been included in table 2. 

 Aboard the Manning they were made simultane- 

 ously with the photometer measurements and 

 have been included in table 7. 



Observations by the Charter Vessels 



Each charter vessel was provided with buck- 

 et thermometer and a Secchi disc. They made 

 surface temperature observations to the nearest 

 half degree every four hours while underway 

 and after each albacore school had been worked. 

 The observed temperatures are not included in 

 this report but have been used in constructing 

 the surface temperature plot, figure 28. 



3/ 



— Weston Photronic Photoelectric Cells, 



Weston Electrical Instrument Corporation Cir- 

 cular B-27-A, February 1949. 



