Figure 2.--A pair of Hypoplectrus guttavarius engaged in courtship at a 

 typical spawning site (Deep Reef at East Wall of Salt River Canyon, 

 HYDROLAB site). 



The disturbance manipulations were conducted the day after baseline 

 spawning behavior was determined. The manipulation was to disrupt the spawning 

 act each time the fish attempted it. As the pair began to enter the spawning 

 clasp, the observer swam rapidly toward the pair (in an attempt to mimic a 

 predator's behavior). The pair was harassed repeatedly this way for as long 

 as spawning was attempted. When mates parted, close watch was maintained 

 until it was certain that spawning had ceased for the night. Occasionally, a 

 pair would separate, swim several meters apart, return several minutes later, 

 rejoin and attempt to spawn again. Follow-up observations were made on the 

 same pair the day after the manipulation. Data analysis of treatments used 

 the nonparametric Mann-Whitney U test statistic. 



On any given day, at least three diver/observers were engaged in various 

 phases of the manipulation. To provide control observations, a diver watched 

 a spawning pair without interfering while other divers were either harassing 

 a spawning pair or conducting follow-up observations. 



74 



