clamping the net line to the towing cable with the 45 kg terminal 

 weight about 10-15 m below the surface. The net was lowered to 

 ca . 210 m depth by paying out 300 m of wire over a 6 minute 

 period (35 m of depth/min.). After fishing at depth for 30 

 seconds, the net was retrieved at 20 m/min. (14 m depth/min.). 

 The angle of stray of the towing cable was recorded every 3 

 seconds and maintained at 45° (+3°) by adjusting the ship speed 

 and course. After reaching the surface, the net was washed down 

 and the samples preserved in 5% formalin buffered with sodium 

 borate. Flowmeter readings were made at the beginning and end of 

 each tow. Detailed descriptions of gear and methods are given by 

 Kramer et al . (1972), and Smith and Richardson (1977). 



LABORATORY PROCEDURES 



Laboratory processing began with the determination of a 

 displacement volume for each sample (methods described in Staff, 

 SPFI, 1953 and Kramer et al., 1972). Sorting involved the 

 removal of ichthyoplankton from the sample and identification and 

 separation of: eggs and larvae of Pacific sardine and northern 

 anchovy; larvae of Pacific hake; and eggs of Pacific saury. Some 

 samples were fractioned into aliquots using a Folsom plankton 

 splitter (McEwen et al., 1954) prior to sorting. Criteria for 

 fractioning were: 1) samples taken at a distance greater than 

 200 nautical miles from shore were not fractioned, 2) samples 

 taken closer than 200 miles from shore and containing 25 ml of 

 plankton or less were not fractioned, and 3) samples taken closer 

 than 200 miles from shore and containing more than 25 ml of 

 plankton were fractioned to 50% of their original volume (J. R. 

 Thrailkill, pers. comm.). Aliquot percentages for fractioned 

 samples from 1975 are listed in Table 1 under the "Percent 

 Sorted" column; 67.9% of samples collected in 1975 were 

 fractioned. 



A "standard haul factor" (SHF) was calculated for each tow 

 to make them comparable and allow estimations of areal abundance. 

 This factor adjusts the number of eggs or larvae in a haul to the 

 number in 10 m of water strained per meter of depth fished. If 

 the vertical distribution of the species has been encompassed. 

 then the adjusted value is equivalent to the number under 10 m 

 of sea surface. The SHF is calculated for each haul by the 

 formula : 



SHF = 10 D 

 V 



where D = depth of haul = cosine of the average angle 

 of stray of the towing cable multiplied by 

 cable length (m) 



3 

 V = total volume of water (m ) strained 



during the haul 



