data did show a difference between the two shades, significant at 

 the 987o level (two-tailed) . 



Role of Sound and Sight 



Along with the color series, the strings and clear models were run in 

 an effort to demonstrate the extent to which sound was triggering the 

 escape response. Neither model provoked reactions at distances 

 significantly different from those of the light models. The strings 

 model was designed to produce turbulence and thus sound, and the 

 clear model should have produced the same sound as opaque models, but 

 a less noticeable visual stimulus. Thus these results are ambiva- 

 lent. In an abbreviated series of experiments in which closed circuit 

 rebreather units were used by the experimenters, in lieu of the normal 

 open circuit SCUBA, there was a tantalizing, but not highly signifi- 

 cant indication that the fish were more tolerant of relatively quiet 

 visual stimuli, but less tolerant of noisy ones. 



Natural Behavior 



Divers spent a total of 33 hours stationed near Chromis schools, 

 filming or taking notes on natural behavior of the fish, while sub- 

 jecting them to as little disturbance as possible. In addition, 

 about half of the time during experiments was available for obser- 

 vation of responses to natural stimuli. The site of most of the 

 observations was a cleaning station and was visited by many species of 

 fish. The reactions of the local school of Chromis to these visitors 

 were noted. 



Whenever a large bar jack ( Caranx ruber) arrived, the Chromis 

 exhibited escape responses indistinguishable (on film or to a diver) 

 from those elicited by fast model approaches. Similar escape re- 

 sponses were elicited by the arrival of schools of up to 50 small 

 jacks, although the reaction was not as rapid or distinct. We have 

 never observed aggressive action of small or large jacks toward the 

 Chromis , but they are known to prey on small fish, Chromis also 

 reacted to the presence of the trumpetf ish ( Aulostomus maculatus) , 

 which we did observe eating them. The slow approach of the trumpet- 

 fish caused the Chromis to swim gradually toward the home coral head 

 and remain there until it departed. 



The lizardfish, ( Synodus sp .), which is cryptically colored and was 

 seldom noticed by observers until it had attacked, was a successful 

 predator on Chromis. It attacked suddenly from below, and while the 

 Chromis reacted to this lunge with an escape response, they were 

 unsuccessful in avoiding the attack much of the time. 



The majority of other fish in the area caused few escape responses. 

 This was surprising, since some of them were large (grey angelfish. 



VI-206 



