COLIN: VARIATION IN MASS SPAWNING OF STRIPED PARROTFISH 



for about 1 min, moved slowly with the current 

 (and presumably with the eggs), and dispersed 

 quickly returning as individuals to a position 

 closer to the substrate. Whether dispersion of the 

 released eggs, depletion of the eggs by feeding, or 

 some other factor caused cessation of the feeding 

 by Chromis cyaneus and Clepticus parrai is not 

 known. A few hundred predators, each ingesting 

 at least one egg every few seconds for periods of 

 nearly 1 min, could eliminate a significant portion 

 of the eggs released in any given spawning rush. 

 These groups of egg predators form after only a 

 small percentage of spawning rushes. During the 

 "epidemic" rushes of summer periods, there are 

 too many eggs released at several locations for 

 these predators to significantly deplete the 

 number released. During winter periods when 

 rushes were few, there did not seem to be sufficient 

 gamete release for the egg predators to wait for 

 rushes to occur and consequently no predation on 

 eggs was observed during these periods. The pre- 

 dation on newly released eggs of S. croicensis is 

 obviously an intentional activity of the predators, 

 not a chance occurrence, but probably serves only 

 as a "bonus" for these fishes which normally spend 

 lengthy portions of the day feeding on particulate 

 zooplankton in the water column (Davis and 

 Birdsong 1973). 



DISCUSSION 



The mass spawning behavior of S. croicensis is 

 similar to that described for Sparisoma rubripinne 

 by Randall and Randall ( 1963). The movement of 

 the population to the deep-reef area in the early 

 afternoon, its behavior before and during rushes, 

 the epidemic rushes, and other behavior is nearly 

 identical. This similarity in mass spawning be- 

 tween genera lines in parrotfishes is interesting. 



It would be most informative to know the num- 

 bers needed before both foraging aggregations and 

 striped phase spawning aggregations occur. Small 

 groups of 15-20 Scarus croicensis have been seen 

 moving together between bouts of feeding, but 

 seem easily deterred by damselfishes defending 

 territories. 



At least on the north coast of Jamaica, mass 

 spawning probably contributes most of the eggs 

 produced by S. croicensis. Pair spawning was 

 never observed in the vicinity of Discovery Bay 

 although terminal phase males were present but 

 never abundant. The summer season is certainly 

 the most active reproductive period. 



The occurrence of mass spawning by parrot- 

 fishes at specific locations on the reef is a relatively 

 long-term phenomena. In the present case nearly 

 4 yr have elapsed since the initial encounter with 

 the spawning group and the location of spawning 

 has not varied. More interestingly, the spawning 

 location of Sparisoma rubripinne at Reef Bay, St. 

 John, investigated by Randall and Randall (1963), 

 was visited in March 1977. Following the direc- 

 tions provided by those authors, a group of approx- 

 imately 200 S. rubripinne were found engaged in 

 spawning during the late afternoon. The presence 

 of a spawning aggregation in what is be- 

 lieved the identical location on the reef after 17 yr 

 in similar numbers to that previously reported 

 indicates a stability and importance of spawning 

 locations not previously documented. The occur- 

 rence of spawning by S. rubripinne on 3-4 March 

 extends the period reported by Randall and Ran- 

 dall ( 1963) and supports their belief in year round 

 spawning. Also the water temperature of 25.8°C 

 was slightly lower than that previously reported. 



The reasons for the abundance of Scarus 

 croicensis compared with some other scarids (such 

 as Sparisoma rubripinne) are difficult to deter- 

 mine. Randall (1967) reported three species of 

 fishes {Mycteroperca interstitialis, M. venenosa, 

 and Caranx ruber) which definitely preyed on 

 Scarus croicensis; however, individals of Scarus 

 (not identifiable to species) were found in guts of 

 several other predatory fishes. Ogden and 

 Buckman (1973) added Epinephelus striatus and 

 Scomberomorus regalis as predators of Scarus 

 croicensis. Due to overfishing, few large predatory 

 fishes are found on the outer reef at Discovery Bay. 

 Indeed, few of the larger species of Scarus and 

 Sparisoma occur there for the same reason. This 

 may be an important factor allowing relatively 

 high numbers of Scarus croicensis to occur there 

 and schooling behavior to be effective in over- 

 whelming the defenses of territorial herbivores. 



Alevizon and Brooks (1975), in examining two 

 coral-reef fish assemblages (Islas Las Aves, Venez. 

 and Key Largo, Fla. ), found S. croicensis to be only 

 a minor component of one (Florida) and of no con- 

 sequence at the other (Venezuela). Possibly they 

 sampled areas where S. croicensis was not abun- 

 dant. In other areas S. croicensis may be absent, 

 even though the environment seems typical of 

 that in which it normally occurs. At Isla Desecheo, 

 a small ( 1 km^) island 20 km west of Puerto Rico in 

 the Mona Channel, extensive diving operations 

 failed to reveal the presence of S. croicensis even 



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