AREA COVERED 



The regular survey cruises of 1955 covered the area between San 

 Francisco, California, and Cape San Lucas, Baja California (station lines 

 60-157). A much more extensive coverage was obtained on "Norpac" (cruise 

 5508), but the results of this cruise are not included in the present 

 report. The monthly coverage during 1955 is summarized in text table 1. 

 The stations occupied on regular survey cruises are shown in figure 1. On 

 cruises 5509 and 5511, an area off southern California was surveyed inten- 

 sively (table I, supplement). This area was covered four times on cruise 

 5509, twice on cruise 5511. Only a portion of the collections made during 

 these two cruises is included in tables II to VIII. 



Text table 1. — Coverage during 1955 



METHODS OF SAMPLING 



The procedures followed in taking plankton hauls are similar to those 

 outlined in previous reports in this series. Refer particularly to 

 Ahlstrom (1952: 3-6) and Ahlstrom (1953: 4-7). 



The nets are hauled obliquely from approximately 140 meters in depth 

 to the surface (200 meters of wire out at greatest depth), except at shallow 

 stations. The hauls are made at a vessel speed of between one and two knots. 

 The angle of stray of the towing wire is measured continuously during a haul 

 by means of an inclinometer suspended from the boom and riding freely on the 

 wire. We have verified by use of a depth flow unit, that the depth of the 

 plankton net at any instant during a haul can be approximated by multiplying 

 the amount of towing wire out by the cosine of the angle of stray of the 

 towing wire from the vertical. 



