LOEB and ROJAS: ICHTHYOPLANKTON COMPOSITION AND ABUNDANCE 



Net Type Differences 



There are no data available for a direct evalua- 

 tion of catch differences between the vertical 

 Hensen and WP2 net tows. However, comparisons 

 of data from the 1983 WP2 net hauls (Table 3) do 

 not indicate that this net is more or less efficient 

 than the Hensen net. Mean abundances and spe- 

 cies diversity (total numbers of taxa and mean 

 numbers of taxa per tow) are within the ranges of 

 values from Hensen net tows. 



Day-Night Catchi Considerations 



Day and night sample data have been combined 

 for each cruise. Day samples (0600 -1800 hours) 

 outnumbered (generally 55-64%) night samples 

 during all cruises. In nine cases there were non- 

 significant day-night larval catch differences (Z 

 tests, P >0.05) and overall similarity in night: 

 day catch ratios (0.74-1.8:1; mode = 1.2:1). One 

 cruise had a significantly higher night vs. day 

 catch (2.5 X; P < 0.01); this cruise and one with 



Table 3. — Abundance estimates and diversity of larval fishes and abundance estimates of zooplankton collected in July-September 

 samples off northern Chile (18 -24-S), 1964-83^ Larval fish abundances as mean numbers per 10 m^. PL = larvae of commercially 

 important pelagic species; OL = other larval taxa (myctophid, other mesopelagic, and other categories). Number of larvae is total raw count 

 of identified larvae for each sampling period. Larval fish diversity expressed as total number of identified taxa and mean number of taxa 

 per tow. Zooplankton abundance is mean displacement volume (cc/10 m2). N.A. = data not available. 



