MULTIPLE SPECIES ASSOCIATIONS 



During the August and November surveys, a number of multispecies associations 

 were observed which involved birds, mammals, and/or fish. Most of the associations 

 seemed to involve birds and sometimes mammals feeding on fish schools. The more 

 discrete and intensive associations are described below. 



The most notable associations occurred on 20, 21, and 22 August in the STEX 

 subunit near the continental shelf margin (70 to 100 km offshore). The first of these 

 associations was spotted at a distance of over 2 km off the survey tract and appeared as 

 a white "boil" on the ocean where organisms were breaking the surface in a tight group. 

 At closer range a school of fast-swimming fish, apparently feeding on smaller organisms, 

 was observed. It was visually estimated that the fish responsible for the surface 

 disturbances were approximately a half meter in length. They attracted a variety of 

 birds, mammals, and sharks. The animals grouped in the vicinity included 10 to 15 short- 

 finned pilot whales, 50 to 60 spotted dolphins in a tight ball, a flock of 75 to 100 Cory's 

 shearwaters, the only brown booby seen during the surveys, a variety of sharks ranging in 

 size from about 1.5 m to over 4 m in length, and a whale shark (Rhincodon typus) 

 estimated at 13 to 16 m in length. In the course of the three day survey, approximately 

 20 of these disturbances were seen. The close proximity of some disturbances to one 

 another occasionally presented difficulty in describing the activity as single or multiple 

 associations. Only the first of the associations contained mammals, but sharks up to 5 m 

 long and birds were present in most. On 21 August approximately 10 groups were 

 observed, 3 of which included single whale sharks and some of which included Cory's 

 shearwaters, sooty terns, and black terns. Eight groups observed on 22 August included 

 at least three and possibly five whale sharks, sooty and black terns, a masked booby, and 

 Cory's shearwaters. 



The fish schools would periodically surface, forming patches of white, broken 

 water. The sharks generally stayed below the surface. The whale sharks occasionally 

 were seen within the fish schools, but more frequently were 10 to 50 m from them and 

 usually 2 m or more below the surface. 



On 24 August in the NTEX subunit an association involving sperm whales and 

 dolphins was observed. At a position approximately 210 km offshore a group of three 

 adult sperm whales with one calf was observed. The three adults were similar in size, 

 suggesting that they were all females. While circling the whales, a group of about 20 

 dolphins (probably Stenella ; possibly spotted dolphins, S. plagiodon) was sighted at least 

 0.5 km from the whales. The dolphins swam toward and around the whales and gathered 

 behind their flukes. The whales sounded, leaving the dolphins at the surface. 



Also on 24 August, a flock of birds was observed about 65 km off the coast of the 

 NTEX subunit. It included three frigatebirds and nine royal terns, and was joined briefly 

 by one masked booby. The birds were circling over a submerged globular object nearly a 

 meter in diameter, but were not seen to feed. As the plane circled the flock, a group of 

 about 10 bottlenose dolphins was observed swimming toward the flock. The dolphins 

 appeared to be attracted to the bird flock. 



During November flocks of birds, composed primarily of royal terns, were seen in 

 all subunits. These mixed flocks were most abundant and were largest in SFLA where 

 groups of several hundred birds were seen. In SFLA laughing gulls had joined several of 



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