KINDS AND ABUNDANCE OF FISH LARVAE IN THE EASTERN 



TROPICAL PACIFIC ON THE SECOND MULTIVESSEL EASTROPAC 



SURVEY, AND OBSERVATIONS ON THE ANNUAL CYCLE OF 



LARVAL ABUNDANCE 



Elbert H. Ahlstrom^ 

 ABSTRACT 



This is the second and concluding paper dealing with kinds and abundance of fish larvae 

 in the eastern tropical Pacific based on collections made on EASTROPAC survey cruises. 

 Main emphasis is placed on the composition and abundance of fish larvae on the second 

 multivessel EASTROPAC cruise, occupied by three research vessels during August-Sep- 

 tember 1967. This cruise, spaced 6 months after EASTROPAC I, affords interesting 

 comparisons of composition and relative abundance of fish larvae during two contrasting 

 periods of the year. Counts of fish larvae per haul on EASTROPAC II were about 50% 

 greater than on EASTROPAC I; species composition, however, was strikingly similar 

 in the two surveys. 



A portion of the EASTROPAC pattern, lying between long 119° to 98° W and lat 20°N 

 to 3°S, was covered on four additional monitoring cruises — providing coverage of this 

 more restricted area on six cruises, spaced at 2-month intervals, between February 1967 

 and January 1968. Essentially the same kinds of fish larvae were taken on each of the 

 six coverages of the monitoring pattern, and for most species the range in relative abun- 

 dance during the annual cycle was 3X or less. 



This report deals with the composition and 

 relative abundance of fish larvae in the eastern 

 tropical Pacific Ocean collected on the second 

 multivessel survey cruise made as part of EAS- 

 TROPAC, during August-September 1967. For 

 brevity, the cruise is referred to in this report 

 as EASTROPAC II (ETP II) . This cruise, con- 

 ducted 6 months after EASTROPAC I (ETP I), 

 deals with the composition of fish larvae at a 

 contrasting period of the annual spawning cycle 

 in tropical waters (Ahlstrom, 1971). 



Three research vessels participated in ETP II: 

 Washington operated by the Scripps Institution 

 of Oceanography occupied the outer pattern, 

 Undaunted of the National Marine Fisheries 

 Service occupied the middle pattern, and Rock- 

 away operated by the Coast Guard took the in- 

 ner pattern (Figure 1). 



' National Marine Fisheries Service, Southwest Fish- 

 eries Center, P.O. Box 271, La Jolla, CA 92037. 



Manuscript accepted February 1972. 



FISHERY BULLETIN: VOL. 70, NO. 4, 1972. 



The coverage during ETP II was less exten- 

 sive than that of the four vessels of ETP I. One 

 major line of stations of ETP I was omitted from 

 ETP II, that along long 126°W, and the coverage 

 below the equator was abbreviated in the two 

 outer patterns, with lines ending at lat 10°S 

 or 5°S. 



Comparison of the composition, relative 

 abundance, and distributions of fish larvae at 

 diflferent periods of the year in tropical waters 

 is a primary objective of this report. The major 

 comparison is with fish larvae obtained on ETP I 

 (Ahlstrom, 1971); all of the 355 ETP II col- 

 lections and an equivalent number of ETP I 

 collections can be used to show similarities and 

 diflferences in the composition of the larval fish 

 fauna during two contrasting periods of the 

 year. 



A portion of the EASTROPAC pattern was 

 occupied by the National Marine Fisheries Ser- 

 vice research vessel, David Starr Jordan, on 



1153 



