CLARKE: SPAWNING, EGG SIZE, AND DEVELOPMENT OF HAWAIIAN ANCHOVY 



total development time. Small nehu larvae feed 

 only during the day (Burdick 1969; Johnson 

 1982). In September, December, and March, lar- 

 vae reached first-feeding status at or shortly 

 before sunrise, could begin feeding as soon as 

 they were able, and had an entire day to feed 

 before having to survive the next night. In June, 

 however, the larvae reached first-feeding status 

 near sunset, had little or no chance to feed, and 

 had to survive the night mostly or solely on 

 internal reserves. Nehu larvae would face situa- 

 tions similar to June whenever the total time 

 from spawning to first-feeding status was close 

 to a multiple of 24 hours. (Other such periods 

 would have occurred between September and 

 December, between December and March, and 

 between March and June.) If larvae during such 

 periods had exhausted then- internal reserves 

 before they had a chance to feed, survivorship 

 could have been greatly reduced compared with 

 periods when larvae reached first-feeding status 

 near dawn. 



The time between reaching first-feeding 

 status and irreversible starvation of nehu larvae 

 is not known. It is usually of the order of days for 

 fishes from higher latitudes (Hunter 1981), but is 

 probably considerably less for nehu given that 

 their incubation and development times are 

 much shorter than those of most higher latitude 

 species. Houde (1974) found that survival and 

 growth of larvae of Anchoa mitchelli at 22°-28°C 

 was unaffected by delaying feeding up to 24 

 hours or more after development of eye pigmen- 

 tation, but nehu may be less tolerant. The devel- 

 opment time between hatching and feeding 

 status is longer for nehu than for A. mitclielli at 

 similar temperatures, and visible yolk is gone at 

 an earlier stage in nehu. 



The seasonal changes in total time between 

 spawning and reaching first-feeding status thus 

 could result in fluctuations of mortality rates of 

 nehu larvae throughout the year independent of 

 either food supply or predation rates. Such fluc- 

 tuations would not be expected in species from 

 higher latitudes because differences of a few 

 hours between reaching first-feeding status and 

 the opportunity to feed are probably not as criti- 

 cal. Furthermore, spawning in many species, 

 e.g., the northern anchovy, Engmnlis mordax, 

 is not as synchronous as in nehu and is spread 

 over a broader portion of the diel cycle (Hunter 

 and Macewicz 1980). Consequently, larvae from 

 a given day's cohort would reach first-feeding 

 status at various points during the diel cycle 

 regardless of the absolute duration of the period 



between spawning and HF status. 



ACKNOWLEDGMENTS 



I thank K. C. Landgraf for his reliable and 

 capable assistance in this study. This research 

 was supported by the University of Hawaii Sea 

 Grant Progi-am (PM/M-20 and PM/M-lBBl) and 

 by the Hawaii Institute of Marine Biology. 



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