FISHERY BULLETIN: VOL. 74, NO. 4 



and to explain the distributions in terms of envi- 

 ronmental parameters. Biomass of total pelagic 

 fish wsLS estimated acoustically (Thorne et al. in 

 press). Partitioning it by species was to be based 

 on the following: contemporaneous catches by 

 fishing or fishery research vessels, samples of fish 

 taken by the CUEA ships, fish eggs and larvae 

 from the zooplankton catches of the CUEA ships, 

 and the literature. In the outcome, only the fish 

 eggs and larvae (ichthyoplankton) were useful 

 during the cruise. Good information on fish catches 

 by other vessels was not received until many 

 months later, sampling from the CUEA ships was 

 unproductive for adults of e'pipelagic species, and 

 the literature did not resolve all questions. The 

 ichthyoplankton results and the fish catches 

 agreed as to the principal species present in 

 different parts of the area. Acoustically detected 

 concentrations of fish (Thorne et al. in press) were 

 identified accordingly. 



This paper gives the principal results of work on 

 the eggs and larvae. It then uses the egg distribu- 

 tions to estimate contemporaneous distributions 

 of adults of some species and compares those with 

 data from contemporaneous fish catches and the 

 literature. Finally the paper attempts to explain 

 the distributions of an abundant species, Sardina 

 pilchardus (Walbaum), according to environmen- 

 tal data collected at the same time as the eggs. 



MATERIAL AND METHODS 



Zooplankton 



The fish eggs and larvae were sorted from the 

 zooplankton catches made during JOINT-I and 

 partly identified by Blackburn. Most of the 

 identifications were made later by Nellen. The 

 zooplankton catches were made and processed, 

 apart from the ichthyoplankton, by R. I. Clutter. 

 Some observations on the zooplankton in general 

 are relevant in this study. A more complete report 

 on JOINT-I zooplankton will appear elsewhere. 



The net hauls for zooplankton were m^ade ver- 

 tically from 200 m or the bottom, whichever was 

 less, to the sea surface. Two cylindro-conical, 

 nonclosing Bongo plankton nets mounted side by 

 side were used. Each net had a mouth diameter of 

 60 cm and a uniform mesh size of 102 /xm. Nets 

 were lowered at 40 m/min and hauled up at 60 

 m/min. A calibrated digital flowmeter was 

 mounted in the mouth of each net. Volume of 

 water filtered by the two nets ranged from 12 to 



158 m-^, depending mainly upon the haul length. 

 Only one net was used in series 1 and 2 (Table 1). 



Processing was as follows, with exceptions 

 shown in footnotes to Table 1. The catches from 

 the two nets were immediately combined and 

 suspended in water. The suspension was shaken 

 and four V4-aliquots were decanted. Each of two 

 aliquots was filtered through a series of sieves 

 (mesh sizes 1,050, 505, 223, and 102 jum) until no 

 more water dripped. This procedure yielded sub- 

 samples of zooplankton in four size ranges, ap- 

 proximately 100 to 200, 200 to 500, 500 to 1,000, and 

 > 1,000 jum. The subsamples from one aliquot were 

 scraped from the filters, blotted on paper towels 

 until no more water appeared, and weighed. The 

 subsamples from the other aliquot were washed off 

 the filters and preserved in Formalin.-^ The fish 

 eggs and larvae were sorted from the preserved 

 500- to 1,000- and >l,000-jLim samples and com- 

 bined. The four wet weights per haul were stan- 

 dardized in grams under 1 m- of sea surface. 

 Allowance was made trigonometrically for effects 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



23-24 MARCH 1974 (ALONG ~2I''40'N) 



SARDINE EGGS/m2 



1808 



ANCHOVY EGGS/m2 a 



_o Q 



ZOOPLANKTON 100-500^ g/m2 



B  B Bfi 



ZOOPLANKTON >500/i g/m2 



_S. 



I 



1000 

 -800 



600 



400 



200 







200 







50 





 -100 

 - 50 



.^_ 



CHLOROPHYLL mg/m2 



1 



300 

 -200 

 - 100 



200 



W I7''40' 



17" 30 



I7">20 



I7»I0 



ir-oo 



Figure 2.— Distribution of sardine eggs, anchovy eggs, and 

 environmental parameters along lat. 21°40'N on 23-24 March 

 1974 (series 5 in Table 1). 



886 



