times several hundred miles apart, the 1958 

 stations were generally 30 miles apart in 

 the area investigated, regardless of whether 

 fishing sets were made. 



Plankton . — The plankton program was 

 augmented by the use of a reduced model of 

 a modified Isaacs-Kidd trawl used by the 

 University of Washington in the North Pa- 

 cific in 1957.1/ The split vertical hauls 

 utilizing the standard 1/2-meter net were 

 replaced by vertical hauls from 150 meters 

 to the surface as a contribution to joint 

 work, and from 300 meters to the surface 

 for comparison with last year's samples. 



Water samples . — The general spacing of 

 Nansen bottles remained the same. However, 

 oxygen samples were obtained from every 

 depth sampled instead of at only alternate 

 depths. No attempt was made to obtain 

 phosphate samples, which proved to be im- 

 practical last year because of limitations 

 imposed by the small vessels and the work 

 load. 



At a temporary laboratory in Adak, 

 salinity and oxygen samples were analyzed 

 to afford early information on oceanographic 

 conditions and to permit re-use of the 

 limited number of available bottles. 



Drift bottles . — We did not emphasize 

 the drift bottles, as the possibility of 

 recovery is limited because of the sparse 

 population and the nature of the coastlines 

 of the Aleutians. However, 491 bottles were 

 released. It was suggested that fish hooks 

 or drag lines be attached to the bottles so 

 that they could be caught in gill nets by 

 high-seas fishing fleets, but time did not 

 permit incorporating this feature. 



Acknowl edgments 



Ralph W. Riley assisted in the chemical 

 analyses. Dr. Richard H. Fleming of the 

 University of Washington permitted us to use 

 the IBM interpolation program, and Cuthbert 

 M. Love and Robert T. Gregory assisted in 

 the IBM programming. Captain John Horton, 



V See William Axon, Preliminary Report of 

 Midwater Trawling Studies in the North 

 Pacific Ocean , University of Washington, 

 Department of Oceanography Technical 

 Report 58. 



USN, provided laboratory space at the U. S. 

 Naval Air Station, Adak, Alaska. 



VESSELS AND OBSERVERS 



As in 1957, davits and portable hydro- 

 graphic winches operated by power take-offs 

 were installed aboard halibut schooners to 

 facilitate handling of oceanographic equip- 

 ment. The vessels, periods of operation 

 (defined by days in port), amd oceanographic 

 observers were as follows: 



M/V Pioneer 



Glenn Ptdersen 



Departed Seattle, 7 May 



Kodiak, 14 May 



Adak, 22-25 May 



Adak, 13-15 June 



Adak, 2-4 July 



Adak, 29 July - 3 August 



Sand Point, 17 August 



Returned Seattle, 31 August 



HA Attn 



Charles Hebard 



May 



Departed Seattle, 7 



Sand Point, 17 May 



Adak, 22-25 May 



Adak, 11-14 June 



Adak, 3-9 July 



Adak, 31 July - 3 August 



Unalaska, 12-14 August 



Returned Seattle, 31 August 



FIELD PROCEDURE 



Stations 



Oceanographic stations are designated 

 as primary or secondary stations. Primary 

 stations occurred at the fishing locations 

 and included hydrographlc casts to 1050 

 meters, a BT trace, vertical plankton hauls, 

 and midwater trawls. Secondary stations 

 included only a BT trace and a bydrograpbic 

 cast to 325 meters. 



Field Routine 



On the approach to a fishing location, 

 the routine at a primary station commenced 

 with a stepped trawl towed at three knots 

 from the surface to four depths (25, 50, 

 100, 150 meters) at 3-minute intervals for 

 a total of 15 minutes, at which time the 

 vessel was stopped and the trawl retrieved 



