RECRUITMENT PATTERNS IN 

 YOUNG FRENCH GRUNTS, HAEMULON FLAVOLINEATUM 

 (FAMILY HAEMULIDAE), AT ST. CROIX, VIRGIN ISLANDS' 



W. N. McFarland,2 E. B. Brothers.^ j. C. Ogden," M. J. Shulman,^ 

 E. L. Bermingham," and N. M. Kotchian-Prentiss' 



ABSTRACT 



During 1979 and 1980 the settlement of postlarval ji^runts (mostly French grunts, Haemulon flarolinentuw) 

 from the plankton to inshore areas in Tague Bay, St. Croix, Virgin Islands, was monitored. Settlement 

 occurred at all times of the year, but showed two distinct maxima during May-June and October-November. 

 Summer settlement rates were approximately one-third the peak rates, whereas winter settlement rates 

 were low but always present. A dominant, semilunar periodicity in the settlement of the postlarvae was 

 clearly present, but smaller interspersed weekly peaks occurred. Calculation of the fertilization dates of 

 recently settled postlarval grunts, derived from otolith ages, also established a dominant 1 5-day periodicity, 

 but again interspersed with smaller weekly fertilization peaks. The phase of settlement and fertilization is 

 most strongly associated with the quarter moons and/or intermediate daily excursions of the tides; the 

 smaller weekly peaks are more closely associated with new and full moons. The pelagic existence of French 

 grunts is about 15 days, suggesting that fertilizations that lead to successful recruitment to inshore areas 

 precede settlement by 15 days. Two hypotheses -semilunar shifts in spawning versus a more constant daily 

 rate of reproduction -are discussed as possible explanations of the dominant semilunar rhythm observed in 

 the settlement patterns. 



Community structure is primarily determined by 

 predation, competition, environment, and patterns 

 of reproduction and recruitment (Ricklefs 1979). In 

 most marine fishes the larval stages are planktonic, a 

 circumstance especially true for tropical reef fishes 

 (Breder and Rosen 1966; Sale 1980; Thresher 1984). 

 In general, larger reef species produce numerous but 

 relatively small eggs, which at spawning are dis- 

 persed into the plankton; whereas smaller reef 

 species produce fewer but larger demersal eggs, 

 which are guarded until hatching when the larvae 

 also "escape" into the offshore plankton community 

 (Johannes 1978; Barlow 1981). The potential 

 significance of this widespread reproductive strategy 

 to affect coral reef fish assemblage structure is wide- 

 ly recognized (see Helfman 1978 and Sale 1980 for 

 reviews). Most ecologists have assumed that 



^Contribution No. 70 of the West Indies Laboratory. 



^Section of Ecology and Systematics, Division of Biological 

 Sciences, Cornell University, Ithaca, Wi 14853. 



^Section of Ecology and Systematics, Division of Biological 

 Sciences, Cornell University, Ithaca, NY 14853; present address: 3 

 Sunset West, Ithaca, Wi 14850. 



"•West Indies Laboratory, Fairleigh Dickinson University, Chris- 

 tiansted, St. Croix, VI 00820. 



^Department of Zoology, University of Washington, Seattle, WA 

 98195. 



^Department of Biology, University of Massachusetts, Boston, 

 MA 02125. 



'Department of Zoology, University of Maine, Orono, ME 04473. 



Manuscript accepted October 1984. 

 FISHERY BULLETIN; VOL. 83, NO. 3, 1985. 



planktonic larval fishes provide an extensive reser- 

 voir of potential recruits that settle to the reef 

 whenever space becomes available (Sale 1977, 1978; 

 Dale 1978; Smith 1978). Virtually all recent studies, 

 however, emphasize that we know little of the 

 ecology of larval fishes at sea and of their patterns of 

 recruitment to benthic juvenile habitats (McFarland 

 in press; McFarland and Ogden in press). Until more 

 quantitative information on the early life history of a 

 variety of species of reef fishes is available, models 

 that "explain" fish community structure remain, at 

 best, first approximations. Here we describe spatial 

 and temporal patterns of recruitment in the French 

 grunt, Haeviulonflavolin£atum, a dominant western 

 Atlantic tropical reef species. 



MATERIALS AND METHODS 



Recently settled postlarval French grunts and 

 white grunts, H. plumieri, standard length (SL) ca. 

 8.5 mm, are commonly observed in schools over 

 grass beds or associating with coral clumps and 

 gorgonians in Tague Bay, St. Croix, VI. Single in- 

 dividuals and larger aggregations associate with 

 structure and/or intermix with schools of mysids 

 (McFarland and Kotchian 1982). There is little diffi- 

 culty in recognizing and counting these very small 

 grunts in the field because they lack the body colora- 



413 



