34 



underwater behavior. On some Beta scientists observed from the helicopter, 

 and during all Bets photograph; of some phase of the operation was don.-. 



The following is a description Of the general behavior of tuna and porpoise 

 relative to the Ashing operation. Since data analysis is only beginning, the 

 conclusions are subject to change <i»d refinement. 



PRl -I II AM HI HAVIOR 



Porpoise schools, at least in the areas ti-hed, are normally found by spotting 

 bird Socks thrOUgb high powered hinoeiilars since birds are seen before the 

 porpoise Which are over the horizon. A majority of the schools found responded 

 to the helicopter when it was sent out to determine if the school was carrying 

 flsh. In one case, a porpoise school was observed that did not seem to be 

 affected by the helicopter. This school was spread out over a large expanse of 

 ocean ( '.I 6 km ». and was accompanied by a large flock of birds, mostly 

 boobies. The porpoise were very spread out. with perhaps L'O to 30 body lengths 

 between groups or individuals. Group size varied from 1 to 5 animals. There was 

 no apparent orientation to the school, and animals moved in all directions. 

 Some animals may have been feeding since they dove deeply enough to 

 disappear from Bight. Other animals moved about in the school and stayed 

 shallow enough so that they were always visible at least over the short periods 

 i about 1 minute) that it was possible to watch one individual or group. Only 

 a few leaps were observed during a period of 30 minutes over the school. When 

 animals surfaced to breathe, there was only a minor surface disturbance. At 

 one point, the Elizabeth C.J. attempted to move closer to the porpoise and the 

 animals immediately responded to the boat even though she was 5 to 7 km 

 distant. When the vessel stopped, the animals returned to their previously- 

 described behaviors. When disturbed, the porpoise all oriented to the same 

 heading and moved quite rapidly on a course that would have taken them across 

 the bow and away from the ship. Some individuals traveled with long, low 

 leaps that caused considerably more surface disturbance than had been seen 

 from the undisturbed animals. At the end of each leap the animal would move 

 under the water for a distance of about 5 body lengths or more before surfacing 

 again in a long, low 7 leap. Most individuals, however, broke the surface only 

 momentarily with just their dorsal surface before resubmerging. There were all 

 gradations between the surfacings. While underwater the animals generally 

 remained visible to the airborne observer. 



During these observations, tuna were occasionally visible. Usually, they were 

 seen only as a dark spot or, if the sun was at the proper angle, one could once 

 in a while see a "shiner". There was no particular, recognizable relationship 

 between the tuna and the porpoise schools, except that they were in the same 

 area. 



CHASE BEHAVIOR 



■ 



The chase began with the launching of speedboats. The speedboats normally 

 operated ahead of the tuna seiner, and were directed by the captain either 

 from the mast or from the helicopter. The goal, to compact the porpoise into 

 a relatively dense school, makes it necessary to force the porpoise into running. 

 This keeps them visible because of the splashes created when the porpoise 

 break the water to breathe. The porpoise observed in the areas fished had 

 almost certainly been set on many times previously, and. during the latter 

 portions of the cruise, we entered areas where the so-called "untouchables" are 

 found. It was thus not possible to observe the responses of naive porpoise to 

 any of the fishing operation. However, a considerable range in behavior was 

 observed during the chase. Some schools, even large schools of 1000 or so 

 porpoise, were rather easily herded. The animals ran well and did not dive if 

 approached too close by a speedboat. Other schools, particularly those observed 

 later in the cruise, would break \ip, and smaller groups would head off in all 

 directions. In these untouchable schools, animals would not run no matter what 

 the speedboats or the seiner did. Furthermore, even when they were running, 

 the animals would barely break the surface when coming up to breathe. If 

 crowded these animals would often dive and come up outside of the line of 

 speedboats, or go between the last speedboats and the seiner. 



During the chase, tuna were more easily observable from the helicopter, than 

 they had been during the pre-chase observations. The majority of tuna were 



