Population characteristics of humpback whales in Glacier Bay and adjacent waters: 1997

Gabriele, C; Doherty, J; Andrews, A

We photographically identified 85 individual humpback whales (Megaptera novaeangliae), including 9 calves, in Glacier Bay and Icy Strait between May 24 and August 31, 1997. This is the highest number of whales documented since the monitoring program began in 1985. Two different statistical analyses demonstrated an increasing trend in Icy Strait but not Glacier Bay whale numbers. Thirty-six whales were resident'in Glacier Bay and 23 were resident'in Icy Strait for more than 20 days. Conversely, 26 whales (10 in Glacier Bay and 16 in Icy Strait) were sighted on just one day. We identified capelin (Mallotus villosus) as likely humpback whale prey on five occasions in the study area in 1997, and have determined that prey patches near whales tend to occur at 14-28 m from the surface, with an average vertical extent of 14 meters. We re-sighted 2 juvenile whales that had not previously been identified in the study area, bringing the 1974-1997 total number of returning offspring to 22. The annual proportion of the population composed of known-age whales first sighted as calves appears to be increasing in the study area, as the maturing progeny of area females return and utilize their mothers'home range.