Table 2. --Statistical comparison of data from table 1. Values listed are 

 calculated values of Z using the Mann-Whitney U test. Values marked by * 

 are statistically different at p = 0.05 (critical value for Z = 1.960.) 



a. No. spawning clasps per pair 



b. No. spawning clasps per pair 



per 5 min. 



c. No. moves pair made between 



spawning sites per total 

 no. spawning clasps 



d. Duration of spawning period 



*2.490 

 1.844 



1.627 

 *2.169 



*2.008 

 0.548 



1.278 

 *2.373 



0.245 



1.347 



0.367 

 0.857 



Spawning of Other Hamlets 



Four other hamlets also were observed spawning at the shallow reef site: 

 H. puella , H. unicolor , H. chlorurus , and H^_ nigricans . We did not see mixed 

 mating among - hamlets. Data contrasting aspects of reproduction in these 

 fishes and of H. guttavarius are presented in table 3. However, the data set 

 lacks sufficient detail to allow more than a general indication of how the 

 pattern and timing of reproduction might vary among congeners of hamlets. 



DISCUSSION 



Many diurnal tropical marine fishes that remain active during the evening 

 crepuscular period may risk being eated by piscivores, whose feeding activities 

 generally are believed to increase at this time (Hobson, 1968, 1972, 1974; 

 Domm and Domm, 1973; Major, 1977). This increased threat of predation is 

 reflected in the potential prey's behavior, and most species retreat to 

 shelter, aggregate, or forage closer to the reef (Hobson, 19783, 1978; 

 Robertson and Sheldon, 1979). However, many species also periodically spawn 

 during dusk (e.g., Randall, 1961; Lobel , 1978; Moyer and Nakazano, 1978; 

 Moyer, 1979; Moyer and Zaiser, 1981; Zaiser and Moyer, 1981; Neudecker and 

 Lobel, 1982; Moyer, et al . , 1983). Spawning during the evening crepuscular 

 period is thought to reduce the likelihood of predation on planktonic eggs, 

 since most plankti vorous fishes that select such small prey are inactive by 

 this time. It is noteworthy that the eggs of nestbui lding, demersal -spawning 

 balistid and pomacentrid fishes hatch after dark, whereupon the larvae become 

 planktonic (Allen, 1972; Moyer and Bell, 1976; Ross, 1978; Fricke, 1980; 

 Lobel and Johannes, 1980; Doherty, 1983). Diurnal planktivores consume 

 smaller prey, including eggs, than nocturnal planktivores which infrequently 



80 



