SMITH: SPAWNING BIOMASS OF NORTHERN ANCHOVY 



Table 9. — Continued. 



The anchovy spawns over a small portion of 

 its range apparently while still schooled; it also 

 spawns over a small portion of the day (25%) ; 

 it now appears that most spawning takes place 

 just after the full moon, ca. 20% of the lunar 

 month (Smith).* In addition, the spawning be- 

 havior is highly seasonal with most spawning 

 occurring in the first half-year. Biases result 

 from sampling during a period in which spawn- 

 ing is occurring (Sette and Ahlstrom, 1948, p. 

 520), and similar errors may result from mis- 

 sing or oversampling spawning peak periods or 

 dense small patches. Although patches would 

 tend to disperse toward randomness, this process 

 appears to be very slow relative to the duration 

 of the larval stage. Patchiness persists and may 



* Smith, P. E. Lunar periodicity in the spawning of 

 the northern anchovy {Engraulis mordax) . Unpublished 

 manuscript filed at National Marine Fisheries Service, 

 Southwest Fisheries Center, P.O. Box 271, La Jolla, CA 

 92037. 



be augmented by predation. For this reason, the 

 samples have been pooled to reduce variance 

 wherever possible. Nevertheless, sample sizes 

 range from zero to tens of thousands of larvae, 

 and a pooled summary may still be based on a 

 chance large sample. In all cases, the above 

 error analysis was done with a sample frequency 

 plot in view and all "outlyers" were examined 

 for effect on the sampling question. All samples 

 taken between 1951 and 1960 are listed by fre- 

 quency distribution in Table 8 for sardine and 

 anchovy total larvae. 



Anchovy larvae abundance (Table 9) and 

 sardine larvae abundance (Table 10) for 11 re- 

 gions and the years 1940, 1941, 1949-69, are 

 listed for each region and quarter in which sam- 

 pling took place at standard stations. Figure 8 

 shows the comparison of the regional census 

 estimates and standard haul summations from 

 1951 to 1966 (Ahlstrom, 1968) . The close agree- 



863 



