that they settle at night. We have observed the same nocturnal timing for 

 acronurus larvae on settlement reefs at St. Croix. Recruiting young 

 pomacentrids also seem to appear overnight (Doherty, 1981). But daytime 

 settlement is not precluded. Given the present status of our knowledge of 

 larval fish behaviors, it is difficult to envision how a larval fish avoids 

 settling if by chance it is carried across suitable substrate during the daytime; 

 but, in contrast, how does a larval fish "know" that it should settle at night? 

 Are cues visible, olfactory, or, perhaps, sonic? Certainly, plankti vorous reef 

 fishes are less active at night (Hobson, 1974; Hobson, et al . , 1981; Gladfelter 

 and Johnson, 1983), but filter-feeding sessile invertebrates are most active at 

 night (Sebens and DeReimer, 1977). Obviously, more precise studies are required 

 to evaluate just how important nocturnal settlement is to survival. 



It should be emphasized that recruitment of larvae varies considerably 

 from year to year (Williams and Sale, 1981; Williams, 1983). As Williams 

 states, "One large pulse alone is sufficient to make total recruitment in a 

 year unusually successful." He reminds us as well that a large recruitment of 

 one species does not mean the same for another species, even in the same guild. 



Finally, it has been implicit in the various arguments of recent fish 

 biologists interested in explaining the diversity in coral reef fish assemblages 

 that the offshore plankton provides a huge, although variable, reservoir of 

 potential recruits which is drawn upon when appropriate space opens on the reef 

 (Dale, 1978; Sale, 1978a; Smith, 1978). Perhaps this is so, but Doherty (1981) 

 suggests that at least at certain times the larval pool may not be endless and 

 can be limiting to the maintenance of reef populations. His theoretical model 

 assumes that larval existence for most species is "precarious" at best (see 

 also Johannes, 1978), and this limiting function introduces a high degree of 

 chance into the recruitment process. 



CONCLUSIONS 



From what is currently known about the recruitment of coral reef fishes 

 from the plankton, it seems likely that strong interactions between local 

 currents and the times of spawning exist. The function(s) of this interaction 

 is best explained as a mechanism to both remove eggs and larvae from the vicinity 

 of the reef to reduce predation and to disperse the young to other localities. 

 The possibility of seasonally developed recirculating eddies could lead to 

 local recolonization. Even totally isolated islands could sustain their fish 

 populations by holding larvae in downstream eddies (Emery, 1972), especially if 

 discrete larval behaviors are used to remain in the eddies. What is missing is 

 an unambiguous case that this routinely occurs. 



ACKNOWLEDGMENTS 



Our research as reported in this paper was supported by NSF Research Grant 

 0CE-79-18569. This paper is Contribution Number 128 of the West Indies 

 Laboratory, St. Croix, U.S. V.I. We thank Drs. John Ebersole and Marjorie Reaka 

 for their many critical and constructive comments during the preparation of the 

 manuscri pt. 



44 



