stray of the towing cable was recorded every 30 seconds and 

 maintained at 45° (+3°) by adjusting tne 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 

 Ahlstrom (1953), 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. In 

 1968 each sample was sorted completely. 



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) 



V = total volume of water (m ) strained 



during the haul 



V = R . a • p 



where R = total number of revolutions of the current 

 meter during the haul 



a = area (m 2 ) of the mouth of the net 



p = length of column of water (m) needed to 

 produce one revolution ot the current 

 meter. 



Tow depth, volume of water strained, and standard haul factor are 

 listed in Table 1 for each tow taken during 1968. Detailed 

 descriptions of factors involved in calculating these values are 



