LOEB and ROJAS: ICHTHYOPLANKTON COMI'OSITION AND AHUNDANCE 



A. TOTAL ICHTHYOPLANKTON 



E 

 O 



a. 



t :1 Anchoveta 

 Other PL 

 I I Sordine 

  OL 



B. 



OL CATEGORIES 



II Other mesopeiogic toxo 

 M yctophids 

 Coastal toxa 



* j > \ i j 



83 



Figure 3. — Mean abundance (numbers per 10 m2) of (A) total ichthyoplankton and major PL components and 

 (Bl total OL and major OL components collected off northern Chile (18'-24°S) during July-September sampling 

 periods, 1964-83. 



Between-year comparisons of the species per- 

 centage compositions of total larvae give a wide 

 range of PSI values (3.3-95.0; Table 6A) which 

 primarily reflect similarity in percentages of an- 

 choveta; 51% of these values are moderate to high 

 (e.g., >65). Highest values (91.5-95.0) come from 

 comparisons between 1966, 1970, and 1973 when 

 anchoveta contributed >87% of the larvae. High 



values (80.7-82.5) also result from comparisons 

 between 1964, 1967, and 1969 and result from 

 moderate anchoveta abundance (54.0-71.9%) and 

 relatively similar proportions of other taxa. Low- 

 est values (3.3-31.0) result from comparisons of 

 1983 vs. all other years and reflect the absence of 

 anchoveta larvae in 1983 samples. The 1973 and 

 1983 PSI values are little affected (e.g., <2.3) by 



11 



