Diel Reproductive Timing 



Hypoplectrus guttavarius spawned almost every evening during the study 

 period. Fish were studied at two sites which differed in depth. The deep reef 

 site (20-30 m depth) was occupied by us February 11-15, and the shallow site 

 (10 m depth) from February 20-March 3. We did not see hamlets spawn on two 

 evenings, February 21-22. Observations at the deep site corresponded to the 

 presence of a new moon (February 15). We were at the shallow site during the 

 full moon (March 1). The dates on which hamlets were not seen spawning 

 coincided with the last quarter moon phase (February 22). 



The diel timing of reproduction, relative to sunset, differed for H. 

 guttavarius at the two sites (depths) and lunar phases. The fi£St spawnings 

 at the deep reef site began 50 min before sunset (with a mean, X, and_standard 

 deviation, S.D., of 33 + 1 min) and the last spawnings ended 10 min (X + S.D. = 

 2 + 9 min) after sunset; most spawnings occurred just prior to sunset. Spawning 

 at the shallow reef site commence^ later, 25 min (X + S.D. = 16 _+ 7 min) before 

 sunset, and ended later, 20 min (X _+ S.D. = 3 +_ 6 min) after sunset; here most 

 spawnings occurred just past sunset (fig. 5). Reproduction by fish at the 

 two sites did not differ in any other aspect. 



We did not observe any strong lunar periodicity in the daily spawning 

 behavior of H. guttavarius . However, our data do not allow distinguishing 

 between the possible effects of 1) different phases of the moon during the 

 times that each group was observed vs. 2) the difference in depth and 

 corresponding changes in light levels during dusk. 



Effects of Disturbance on Spawning Behavior 



All H. guttavarius persisted in spawning in spite of overt and constant 

 harassment. Harassed pairs attempted twice as many spawning clasps and 

 continued for about 25 min later than nonharassed (day before and day after) 

 pairs (tables 1, 2). However, the frequency of spawning clasps attempted per 

 5 min remained the same (about 2+1 clasps; tables lb, 2b). The number of 

 times a pair changed spawning sites relative to the number of spawning clasps 

 also did not vary significantly (tables lc, 2c). One particularly striking 

 effect of disturbance on these spawning fish was that, as spawning was 

 continuously disrupted, a pair attempted to spawn progressively nearer the 

 substratum (based on our qualitative observations). At the end of the 

 disturbance period, several pairs were trying to spawn next to the bottom 

 while hidden among coral /gorgonian branches. This result simply may indicate 

 that once ovulation has begun, the fish must spawn. 



Overall, the fish persisted in spawning despite the aggressive behavior 

 of the scuba divers. However, we have no estimate of the fate of zygotes 

 when released next to the bottom and in between coral /gorgonian branches as 

 compared to those normally dispersed about a meter above reef structures. 

 The experience of the disturbance had no apparent lasting effects on the 

 fish. The fish's behavior did not differ markedly on the day after compared 

 to the day before the disturbance (tables 1, 2). 



78 



