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Fishery Bulletin 90(3). 1992 



By late summer, whales typically congregate in 

 Frederick Sound and Stephens Passage where large 

 swarms of euphausiids, primarily Thysonoessa raschii 

 and Euphausii pacifica, are common (Krieger and 

 Wing 1984, 1986). Some whales feed throughout fall 

 and early winter in areas such as Seymour Canal and 

 Sitka Sound where euphausiids and schooling herring 

 appear to remain available (Baker et al. 1985, Straley 

 1990). 



Here we summarize the results of nonsystematic 

 surveys of individually identified humpback whales in 

 southeastern Alaska during the summer and through 

 late fall of 1986. The 1986 surveys were designed to 

 overlap in geographic range and seasonal timing with 

 previous coverage during the years 1979-85 (Baker et 

 al. 1985, Baker 1985b). In keeping with recommended 

 management plans (Anonymous 1984), our surveys 

 documented regional abundance and distribution of 

 humpback whales in areas that may be impacted direct- 

 ly or indirectly by vessel activity in Glacier Bay Na- 

 tional Park. More specifically, we sought to evaluate 

 trends in the abundance, reproductive rates, and 

 primary prey of humpback whales in southeastern 

 Alaska across the years 1979-86. Documentation of 

 long-term trends in these population characteristics are 

 valuable for assessing the influences of human activ- 

 ity, such as mining, logging, or petroleum exploration 

 and development, or natural environmental fluctua- 

 tions such as El Niiio events, on the habitat use and' 

 recovery of this endangered species (National Marine 

 Fisheries Service 1991). 



Methods 



Vessel surveys 



Humpback whales were observed and individually iden- 

 tified primarily in two areas or subregions of south- 

 eastern Alaska (Fig. 1); Glacier Bay and the adjacent 

 waters of Icy Strait (referred to collectively as Glacier 

 Bay); and the contiguous waters of Stephens Passage 

 and Frederick Sound, including Seymour Canal (re- 

 ferred to collectively as Frederick Sound). Photographs 

 of whales were also collected in Chatham Strait and 

 Sitka Sound on an opportunistic basis throughout the 

 summer and fall. 



Whales in Glacier Bay were censused by one of us 

 (CSB) from 22 May to 10 September under the auspices 

 of the National Park Service. A total of 42 one-day 

 surveys were conducted aboard a 17-foot fiberglass 

 boat powered by a 50-hp outboard motor. The lower 

 and middle bay (i.e., from Bartlett Cove to the mouths 

 of Muir Inlet and the West Arm) were surveyed not 

 less than twice and not more than three times a week. 

 The mouth of Glacier Bay and the adjacent waters of 



Figure 1 



Southeastern Alaska region and primary survey areas 

 (shaded). 



Icy Strait were surveyed at least once and not more 

 than twice a week. Study period and survey coverage 

 were designed to overlap and extend previous coverage 

 during the summers of 1982-85 (Baker et al. 1985, 

 Baker 1985b). 



Whales in Frederick Sound were censused during 

 three summer surveys: 31 July-3 August; 29 August- 

 1 September; and 12 September- 15 September. These 

 survey cruises were conducted aboard the RV Sashin, 

 a 22-foot stern-drive vessel provided by the Auke Bay 

 Laboratory, National Marine Fisheries Service. Each 

 cruise originated and ended in Juneau and surveyed 

 the length of Stephens Passage and Frederick Sound 

 south to Cape Fanshaw and west to Pybus Bay (see 

 shaded area, Fig. 1). A fourth survey of Frederick 

 Sound was conducted from 29 November to 9 Decem- 

 ber aboard the MV Fairweather, a 43-foot, diesel- 

 powered cabin cruiser. This cruise originated and ended 

 in Sitka, Alaska, and surveyed the southern half of 

 Chatham Strait and Frederick Sound, north to Sey- 

 mour Canal. The dates and geographic coverage of 

 Frederick Sound surveys were chosen to coincide with 

 those of similar previous surveys during the summers 

 of 1984-85 (Krieger and Wing 1986, CSB unpubl. 

 data), the fall or winters of 1979-85 (Straley 1990), 



