Abstract. — In the summer and 

 fall of 1986 a total of 257 humpback 

 whales Megaptera novaeangliae were 

 individually identified during nonsys- 

 tematic vessel surveys of southeast- 

 ern Alaska. The majority of adult 

 animals (n 130. 54.6%) identified in 

 1986 had been identified previously 

 in southeastern Alaska during the 

 years 1979-85. Capture-recapture 

 estimates suggested that this region- 

 al subpopulation increased in abun- 

 dance from 1979 to 1986, and in- 

 cluded 547 individual whales (95% 

 CL: 504-590) at the time of the 1986 

 surveys. An average reproduction 

 rate of 0.36 calves/mature female- 

 year-' (95% CL: 0.28-0.43) was es- 

 timated for this regional subpopula- 

 tion using individual identification 

 records collected during 1980-86. In 

 the Frederick Sound-Stephens Pas- 

 sage area, the largest number of 

 whales was found during August and 

 their predominant prey appeared to 

 be euphausiids. In the Glacier Bay- 

 Icy Strait area, the relative abun- 

 dance of whales was greatest in June 

 and July and their predominant prey 

 appeared to be schooling fish. Low 

 levels of interchange between sur- 

 veyed areas for much of the summer 

 season indicated strong preferences 

 for local habitats among individual 

 whales. The documented presence of 

 some individual whales for at least 

 6 months is evidence that southeast- 

 ern Alaska is the primary feeding 

 ground for many of the whales iden- 

 tified in these surveys. 



Population characteristics of 

 individually identified humpback 

 whales in southeastern Alaska: 

 Summer and fall 1986 



C. Scott Baker 



University of Hawaii, Pacific Biomedical Research Center 



Kewalo Marine Laboratory, 41 Ahui Street, Honolulu, Hawaii 96813 



Janice M. Straley 



Institute of Marine Sciences, University of Alaska, Fairbanks, Alaska 99775 



Anjanette Perry 



University of Hawaii, Pacific Biomedical Researcfi Center 



Kewalo Marine Laboratory, 41 Ahui Street. Honolulu, Hawaii 96813 



Manuscript accepted 18 May 1992. 

 Fishery Bulletin, U.S. 90:429-437 (1992). 



Humpback whales Megaptera novae- 

 angliae in the central and eastern 

 North Pacific, like those in the west- 

 em North Atlantic (Katona and Beard 

 1990), appear to form several geo- 

 graphically-isolated subpopulations 

 during the summer and fall feeding 

 season (Baker et al. 1986, Perry et al. 

 1990). Following their yearly migra- 

 tion south, individuals from these 

 feeding herds intermingle in the 

 waters of either Hawaii or Mexico 

 during the winter breeding season 

 (Darling and Jurasz 1983, Baker et 

 al. 1985, Darhng and McSweeney 

 1985, Baker et al. 1986). 



The coastal waters of southeastern 

 Alaska (56-59°N lat.) seem to encom- 

 pass the primary feeding ground of 

 a single 'herd' or regional subpopula- 

 tion estimated to number between 

 327 and 421 individual whales as of 

 1983 (Baker et al. 1986). Although 

 the exact geographic boundaries of 

 each herd are unknown, whales from 

 southeastern Alaska appear to re- 

 main segregated from those that 

 summer to the west in the Gulf of 

 Alaska, including Prince William 

 Sound, and those which summer to 

 the south along the coast of central 

 California (Baker et al. 1986, Perry 

 et al. 1990). Fidelity to a particular 



feeding ground appears to be mater- 

 nally directed (Martin et al. 1984, 

 Baker et al. 1987, Clapham and Mayo 

 1987) and may persist across many 

 generations, as suggested by geo- 

 graphic segregation of mitochondrial 

 DNA haplotypes (Baker et al. 1990). 

 Within southeastern Alaska, how- 

 ever, the distribution of whales is not 

 homogeneous and intermingling of 

 individuals is not random (Baker 

 1985a, Baker et al. 1985). Some 

 whales return vdth considerable fidel- 

 ity to specific areas or 'neighbor- 

 hoods' such as Glacier Bay, Sitka 

 Sound or Frederick Sound and, at 

 least during part of the feeding sea- 

 son, may establish restricted local 

 ranges (Jurasz and Palmer 1981, 

 Perry et al. 1985, Baker et al. 1988, 

 Straley 1990). Changes in distribu- 

 tion and local movement v«thin a sea- 

 son appear to reflect changes in prey 

 availability. The relatively early ar- 

 rival of whales into the Glacier Bay 

 area indicates that this may be an im- 

 portant area for early-summer feed- 

 ing on schooling fish, including cape- 

 lin Mallotus villosus, sand lance 

 Ammodytes hexapterus, and Pacific 

 herring Clupea harengus (Wing and 

 Krieger 1983, Krieger and Wing 

 1984 and 1986, Perry et al. 1985). 



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