Seasonal Maximum 20 24 23 ------------------------------------------------------
TABLE 3. Age composition of humpback whales per year in Glacier Bay (modified from Jurasz and Jurasz, 1979)
---------------------------------------------------------- YEAR 1976 1977 1978 ----------------------------------------------------------
TOTAL NO. OF ADULTS 19 19 18 ----------------------------------------------------------
Identifiable humpback whales were sighted in Glacier Bay each year, 1976-1977, for a six to twelve week period. In 1978, all but three whales departed the Bay after 16 days. In the summers of 1976-1978 two influxes of whales occurred (Table 2). The Juraszs' define an influx of whales as those whales that enter and remain in the Bay for a minimum of three weeks. The second influx arrived 7-14 days after extreme low tides occurred in late June-early July and presumably moved into the Bay on flood tides. In 1979, a single influx comprised of 3 whales entered the Bay. The age composition of identified whales using Glacier Bay was categorized by the Juraszs' for 1976-1978 (Table 3).
During the period spent in the Bay, humpback whales have been observed to feed on capelin, euphausiids (_Euphausia pacifica_), and pandalid shrimp (_Pandulus borealis_). There appear to be three generalized feeding relationships: 1) early-season feeding on shrimp in the upper Bay; 2) mid-season feeding by concentrations of whales on capelin in the lower Bay; and 3) late-season feeding (around August 5) by concentrations of whales on euphausiids in mid-Bay.
Behaviorally, humpback whales appear to lunge up through concentrated schools of prey during mid-season and use "bubble-netting" as a means of concentrating less dense and/or numerically fewer prey earlier and later in the season. In other areas of southeast Alaska, humpbacks are reported to also feed on herring (_Clupea harengus pallasi_), shrimp, and possibly other small schooling (swarming) prey. The Juraszs' believe that humpbacks establish feeding territories in the Bay, and have described eight "stress behaviors" associated with violations of those territories (Table 4). The data collected by the Juraszs are extensive (including human use of Glacier Bay) but have not yet been completely analyzed.