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Fishery Bulletin 105(1) 



eas where they were previously identified and stud- 

 ied (Puget Sound to Kenai Fjords), and no interaction 

 was observed in our study between the genetically or 

 acoustically distinguished groups. Therefore, it was 

 possible to infer the population status from the group- 

 association patterns of individuals for which there was 

 no genetic or acoustic data. Animals observed in asso- 

 ciation with whales of known genetic or acoustic type 

 were assumed to be of that same type. We did not use 

 diet as a criterion for classification to avoid circular 

 reasoning (evidence of dietary differences between popu- 

 lations becomes tautological if diet is used to define 

 populations). 



Acoustic analysis During 31 of 39 encounters in which 

 we recorded killer whale vocalizations and did not collect 

 genetic samples, the use of distinct calls, use of echo- 

 location clicks, and the call rate were consistent with 

 attributes of resident killer whale vocalizations from 

 other regions of the Northeast Pacific (Table 2) (Yurk, 

 2005). All encounters had average call rates of three 

 calls or more per minute, and strings of echolocation 

 clicks were abundant across encounters. During these 

 encounters, 23 structurally distinct calls were identi- 

 fied. Seven calls showed no obvious similarities to calls 

 recorded elsewhere in the northeast Pacific and 15 had 

 structural similarities, sharing some call components 

 with calls used by killer whales that regularly occur in 

 the northern Gulf of Alaska. However, no call from these 

 encounters was identical to any call of the known killer 

 whale call repertoires. 



The resident-type killer whales encountered in west- 

 ern Alaska possibly belong to groups that are distinct 

 from the groups of resident killer whales in other re- 

 gions of Alaska because no call syllables or call pat- 

 terns (sequence of syllables) between groups were found 

 to match. Resident killer whales learn their distinct 

 call structures in their maternal group, in which they 

 remain for life, and call structures remain stable and 

 group-specific for more than one generation (Ford, 1991; 

 Yurk et al., 2002). However, because we do not know 

 the complete call repertoires of killer whales in western 



Table 2 



Location and number of encounters that produced record- 

 ings of killer whales (Orcinus orca) used in our acoustic 

 analyses from 2001 through 2004 in the Eastern Aleu- 

 tians and False Pass, Alaska. 



Year 



Location 



Number of encounters 



2001 

 2002 



2003 

 2004 

 Total 



Unalaska 



Unalaska, Akutan Island, 



Umnak Island 



False Pass 



False Pass 



31 

 2 

 3 



39 



Alaska we cannot be sure that we will not find complete 

 call-type matches in the future. 



In eight killer whale encounters that did not yield 

 genetic samples (five from False Pass and three from 

 other areas in the eastern Aleutians), vocal activity or 

 average call rate was considerably lower than the three 

 calls per minute that are typical for residents, and was 

 closer to one or less than one call per minute, which is 

 typical for transient killer whales from other areas of 

 the northeast Pacific (Deecke et al., 2005; Saulitis et 

 al., 2005). Furthermore, all recorded calls showed typi- 

 cal characteristics of transient type calls, such as the 

 quavering of the fundamental sound frequencies and 

 the lower number of call syllables compared to those in 

 calls from resident killer whales. 



The three encounters that were not from the False 

 Pass region (Table 2) contained three distinct calls 

 that were structurally similar but did not show identi- 

 cal order of syllables or identical syntax to calls used 

 by members of the ATI transient community. The ATI 

 transient community is thought to be limited to the 

 Prince William Sound and Kenai Fjords region and to 

 use a distinct call repertoire (Saulitis et al., 2005). 



In the recordings made during five encounters in 

 the False Pass region in 2003 and 2004 (Table 2), 14 

 distinct calls were identified in more than one of the 

 recording sessions. Thirteen of these 14 distinct calls 

 were identified from recordings made during two en- 

 counters in 2003. Ten of these 13 calls were also re- 

 corded during 3 encounters with killer whales in May 

 2004 in the same area. Thus, although the majority of 

 calls recorded in 2004 were already identified in 2003, 

 one new distinct call was found. This high number of 

 same distinct-type calls is typical for transient killer 

 whales (Deecke, 2003). Call repertoires of resident killer 

 whales are generally much larger, and this larger rep- 

 ertoire is likely responsible for the detection of several 

 new calls from newly encountered whales in recordings 

 from consecutive years (Ford, 1991; Yurk, 2005). All 

 call types recorded in the False Pass region appeared 

 to be distinct from calls recorded from transient killer 

 whales in other regions of the North Pacific. However, 

 some structural similarity (in the form of matching call 

 components) was found for some of the 14 calls recorded 

 in our study and for the calls recorded from a transient 

 community that inhabits waters along the west coast 

 of North America. These results may indicate that the 

 transient killer whales we encountered in the eastern 

 Aleutians comprise one or more unique populations or 

 communities that show some acoustic similarity with 

 transient killer whales found in other regions of the 

 Pacific. 



Genetic analysis A total of 93 skin samples were col- 

 lected from 2001 through 2004 by using biopsy darting 

 techniques. Separation of ecotypes based on mtDNA 

 haplotype (Barrett-Lennard, 2000) showed that 47 of 

 the 93 samples were of transient-type lineage, 42 were of 

 the resident-type lineage, and 4 were of the offshore-type 

 lineage. Preliminary classifications of lineages based 



