mix relatively little. Similarly, eggs from spawning sites 500 m apart will mix 

 substantially less than those from closer sites. Coral reef fishes often spawn 

 at sites openly exposed to current that quickly sweeps eggs off the reef (Johannes, 

 1978; Barlow, 1981) and away from later egg masses. These current conditions could 

 restrict genetic mixing. 



In demersal spawners, degree of genetic mixing will be influenced by spatial 

 separation between benthic egg masses, current speed, and the degree of asynchrony 

 of hatching within and between egg masses. If all eggs within one mass hatch 

 synchronously, then young larvae will form a tight clump as they enter the water 

 column. If intra-spawn hatching is asynchronous, sibs will enter the water column 

 at intervals and will be more widely spaced by the currents. If adjacent egg 

 masses hatch hours or days apart, currents will space emergent larvae with relatively 

 1 i ttle mixinq . 



In summary, the eggs of coral reef fishes begin their pelagic existence in 

 small, discrete patches. Egg and larval patches subsequently are found at various 

 stages throughout pelagic life and newly recruiting juveniles or post-larvae may 

 settle in or form aggregations. There are tantalizing hints of strong selection 

 pressures for pelagic eggs and larvae to aggregate, either to increase protection from 

 predation or to enhance the search for food patches. The perceptual and motor 

 apparatus to support active aggregation are available within a few days of hatching. 

 Since coral reef fish eggs hatch rapidly in tropical seas, the total time for which 

 eggs and young larvae are susceptible to passive turbulent diffusion, prior to 

 onset of the ability to form or remain in patches, is short, on the order of 2-5 

 days. This time is substantially reduced, perhaps to zero, for demersal spawners, 

 mouthbrooders, livebearers, and lionfishes, whose eggs remain together throughout 

 egg development and whose larvae hatch at a large size and at a relatively advanced 

 stage. Mixing of eggs released by separate spawning pairs within a local popula- 

 tion will be limited to spawning episodes occurring close together in time and 

 space. The stronger the current at the time of spawning, the closer in space and 

 time successive spawns can be without substantial mixing. All of these factors 

 render it possible, for at least some members of some species, that eggs will 

 remain together throughout pelagic life and release larvae that settle aggregately 

 to form kin groups or groups containing kin on the reef. 



Few of the factors influencing the possibility of kin groups have been thorough- 

 ly examined in coral reef fishes. However, genetic relatedness among individuals 

 on a reef can be studied with existing electrophoretic techniques. Likely places 

 to look for kin groups are among colony-forming demersal spawners, lionfishes, 

 mouthbrooders, livebearers, and fish like Anthias whose young juveniles occupy 

 large, sedentary groups. 



ACKNOWLEDGMENTS 



I wish to thank A. Okubo, A. Mercado and P. Yoshioka for calculations, and 

 R. Appeldoorn, J.Corredor, D. Hensley, M. Leighton-Shapiro, J. Morel 1, and Y.Sadovy 

 for helpful discussion of ideas and criticism of the manuscript. Work was 

 supported by NIH grant S06RR08103. 



BIBLIOGRAPHY 



Barlow, G.W. 1981. Patterns of parental investment, dispersal and size among 



coral-reef fishes. Env. Biol. Fish. 6: 65-85. 

 Brothers, E.B., & W.N. McFarland. 1981. Correlations between otolith microstructure 



growth, and life history transitions in newly recruited French grunts ( Haemulon 



flavolineatum (Desmarest), Haemulidae). Rapp. P.-V. Reun. Cons. Int. Explor. 



Mer. 178: 369-374. 



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