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

 140 m depth by paying out 200 m of wire over a 4 minute period 

 (35 m of depth/min.). After fishing at depth for 3 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 

 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). Zooplankton volumes 

 (including ichthyoplankton) of samples collected in 1951 are 

 listed in Staff, SPFI (1952) and presented graphically in 

 Thrailkill (1956) and Smith (1971). 



Sorting involved the removal of ichthyoplankton from the 

 sample and identification and separation of eggs and larvae of 

 selected species (see introduction) . Usually, each sample was 

 sorted completely; however, some of the samples were fractioned 

 into aliguots using a Folsom plankton splitter (McEwen et al., 

 1954) prior to sorting. Several criteria were used to determine 

 whether a sample was fractioned: samples containing an abundance 

 of thaliacians and coelenterates and exceeding 150 ml in total 

 plankton volume were fractioned (to 50%, 25%, 12.5%, or 6.25%) to 

 approximate a reduced volume of 50 ml for sorting; samples with 

 an excessive guantity of fish eggs and/or larvae were 

 occasionally fractioned to expedite the sorting process in order 

 to meet scheduled deadlines. If the identified fraction of an 

 aliquot yielded rare or interesting species of fish larvae, the 

 remaining fraction was frequently sorted and identified with the 

 intent of finding additional specimens. Aliquot percentages for 

 fractioned samples from 1951 are listed in Table 1 under the 

 "Percent Sorted" column. 



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: 



Personal communication, James R. Thrailkill, National Marine 

 Fisheries Service, Southwest Fisheries Center, La Jolla, CA. 



