Mojica et a/.: Recruitment of Albula vulpes 



673 



Hours of dark flood tide per night 



Figure 7 



Number of bonefish, Albula vulpes, collected versus hours 

 of flood tide occurring under moonless conditions. Most 

 recruitment occurred on nights with >4 hours of flood tide 

 under moonless conditions. 



great majority of recruitment was observed on nights 

 with more than four hours of dark flood tide (Fig. 7). 

 The restriction of recruitment to these windows of 

 opportunity may be responsible for the apparent bi- 

 modality in the age distribution of leptocephali (Fig. 

 6), although larger numbers of organisms need to be 

 examined to test this possibility. Additional work is 

 needed to determine whether onshore movement is 

 concentrated in specific portion(s) of a flood tide and 

 how cloud cover can affect lunar illumination and 

 recruitment. 



Active vertical migration may be the mechanism 

 by which larvae influence the timing of onshore mi- 

 gration (Shenkeret al., 1993). Early larvae were dis- 

 tributed through the pelagic environment of Exuma 

 Sound to depths of 25-50 m (Drass, 1992). Migra- 

 tion of settlement-stage individuals toward the sur- 

 face only under dark night conditions could enhance 

 the entrainment of larvae into onshore tidal and 

 wind-driven flow. The fact that over 90% of the A. 

 vulpes larvae were taken by the channel nets in the 

 upper 1 m of the water column during dark-night 

 recruitment pulses, when only a relatively few lar- 

 vae were found 2-4 m below the surface, indicates 

 that these leptocephali do indeed selectively utilize 

 the surface layer during their onshore movement. 



The recruitment of A. vulpes leptocephali varied 

 greatly among days, months, and years. This vari- 

 ability was generally not correlated with specific wind 

 or shelf-edge current patterns (Table 1), unlike the 

 very close association between a major settlement 

 episode of Nassau grouper, Epinephelus striatus, and 

 a storm event at LSI in February 1991 (Shenker et 

 al., 1993). Recruitment of A. vulpes was thus more 



similar to that of other taxa recruiting near LSI (e.g. 

 Bothidae and Labridae) that showed a lunar period- 

 icity in recruitment but not a strong association with 

 environmental parameters (Thorrold et al., 1994, a 

 and b). The lack of strong correlation between envi- 

 ronmental conditions and recruitment and the high 

 degree of recruitment variability among months and 

 years suggest that the processes controlling the sup- 

 ply of larvae are acting prior to their onshore move- 

 ment in Exuma Sound. These processes span the 

 range from spawning success to larval survival in 

 the pelagic environment and will require additional 

 sampling for evaluation of their potential roles as bottle- 

 necks in the population of A. vulpes in the Bahamas. 



Acknowledgments 



This research was conducted at the Caribbean Ma- 

 rine Research Center's station on Lee Stocking Is- 

 land and was funded by grants from the National 

 Undersea Research Program of the National Oceano- 

 graphic and Atmospheric Administration. The au- 

 thors would like to thank Doug Markle and an anony- 

 mous reviewer for their constructive and insightful 

 comments. Special thanks are due to E. Maddox, H. 

 Patterson, S. Thorrold, and E. Wishinski for their 

 contributions. Otolith analysis was greatly facilitated 

 by using K. Clark's Macintosh work station (NSF 

 Grant BIR 8951326). We thank all of the staff on 

 Lee Stocking Island who assisted with this project 

 and the army of volunteers who made it possible. 



Literature cited 



Bruger, G. E. 



1974. Age, growth, food habits, and reproduction of bone- 

 fish, Albula vulpes, in south Florida waters. Fl. Mar. Res. 

 Publ. 3, 20 p. 

 Chatfield, C. 



1979. The analysis of time series: an introduction. Chap- 

 man and Hall, London. 

 Colton, D. E., and W. S. Alevizon. 



1983. Feeding ecology of bonefish in Bahamian waters. 

 Trans. Am. Fish. Soc. 112:178-184. 

 Doherty, P. J. 



1987. Light traps: selective but useful devices for quanti- 

 fying the distributions and abundances of larval fishes. 

 Bull. Mar. Sci. 41:423^131. 

 Doherty, P. J., and A. J. Fowler. 



1994. An empirical test of recruitment limitation in a coral 

 reef fish on the Great Barrier Reef. Science (Wash. D.C.) 

 263:935-939. 

 Drass, D. M. 



1992. Onshore movements and distribution of leptocephali 

 (Osteichthyes: Elopomorpha) in the Bahamas. M.S. the- 

 sis, Florida Institute of Technology, Melbourne. FL, 85 p. 



