During these joint studies on Pacific bonito a variety of 

 other behavior patterns was observed and classified. Some of 

 these patterns were influenced by how recently the fish had 

 eaten; e.g., one specific mouth movement was observed three 

 times more often among fish which had not eaten recently 



than among those which had just fed. This mouth movement 

 reduces the flow of water over the gills at times when the 

 metabolic rate is low. 



Tunas, as well as many other pelagic fishes, tend to con- 

 gregate in the vicinity of floating logs and other debris on the 

 open ocean. Construction of a raft with an underwater view- 

 ing chamber permitted observation of the behavioral and ecol- 

 ogical interactions of these fishes (fig. 5). During the first 



STfXL STRAPS 



DAY NIGHT 



DRIFTING 



DAY NIGHT 



ANCHORED 



Figure 5. --Exploded view of the observation raft. 

 In use, the observation chamber rides below 

 the waterline. 



Figure 6. --Change in numbers of fishes at raft 

 during day and night, and while it was drift- 

 ing and anchored. 



