found that 20 tended to spawn near or at new moon, 8 at full moon, 13 at times 

 of both new and full moon, and the remaining 11 during quarter moons. 



Several direct observations have related the timing of spawning to specific 

 phases of the moon (e.g., quarter moons, Polydactylus sexfilis , May, et al . , 

 1979; Centropyge potteri , Lobel , 1978). The periodicity in spawning has been 

 interpreted as an adaptation to enhance the chance that the eggs will be flushed 

 by tidal currents away from the reef, and therefore reduce mortality by egg 

 predators, which is commonly observed (Randall and Randall, 1963; Moyer, 1974; 

 Meyer, 1977; Robertson and Hoffman, 1979; Colin, 1978; Robertson, 1983). 



Mortality among the pelagic eggs and larvae is high when compared to the 

 adults (Sale, 1980). Very likely as a response to this high mortality (but 

 perhaps also to increase the probability that some propagules will be dispersed) 

 the fecundity of reef fishes is high, usually in excess of 50,000 eggs per year 

 per female in pelagic spawners (Randall, 1961; Bryan, et al . , 1975; Thompson 

 and Munro, 1978), and greater than 8,000 eggs in demersal spawners (Warner, et 

 al. , 1975; Bell , 1976). 



In addition to varied lunar periodicities, many reef fishes migrate to the 

 deeper areas of the reefs and/or to pinnacles and reef extensions to spawn, and 

 there usually invoke discrete behaviors when spawning (e.g., a rush to the 

 surface to spawn the eggs as far from the reef as possible; Lobel, 1978; Colin, 

 1982). In addition, spawning often shows a daily cycle (e.g., occurring at 

 dusk; Lobel, 1978). These behaviors have been interpreted as acts to reduce 

 egg predation and may be particularly effective because eggs are small, 

 transparent, and therefore difficult to detect, especially at dusk (Hobson and 

 Chess, 1976). Many species, however, spawn during midday or the afternoon 

 (Colin, 1982; Robertson, 1983). 



Although the observations on spawning behavior suggest tactics that can 

 reduce mortality of eggs and improve dispersal away from the reef, few observations 

 are supported by direct measurements of prevailing tides, currents, and other 

 conditions to verify that this is what actually happens. A recent paper by 

 Robertson (1983) combines careful field observations of spawning in seven 

 species of surgeonf ishes at four different localities in the Pacific and Indian 

 Oceans. Readers are referred to the original for the wealth of observations 

 detailed by Robertson. Several general conclusions, however, are important. 

 (1) The various species spawned over different intervals of the day (a few in 

 the morning; most from midday until dusk). (2) Both paired spawnings and group 

 spawnings occurred in several of the species. (3) Except where territorial 

 harems were established, most individuals migrated toward outer and deeper 

 portions of the reefs to spawn. (4) In almost all instances, spawning fishes 

 rose toward the surface to spawn. (5) The most common feature among the seven 

 species was a strong tendency to spawn during ebb tides, as water was flushed 

 off the reef. All of these behaviors would minimize the chance that freshly 

 fertilized eggs would be exposed to plankti vorous reef fishes. Spawning as 

 tides flush water off reefs also was indicated by Randall (1961), Robertson and 

 Choat (1974), Lobel (1978), and Thresher (1979). In contrast, Robertson (1983) 

 found no distinct tidal rhythms in surgeonfish spawnings at Lizard Island where 

 the currents flow parallel to the reef rather than on and off the reef. This 



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