ESTIMATING THE ADULT SURVIVAL RATE OF CENTRAL NORTH PACIFIC HUMPBACK WHALES (MEGAPTERA NOVAEANGLIAE)

We used photo-identification records to estimate annual survival of adult humpback whales (Megaptera novaeangliae) for the central North Pacific stock using models within the software application Program MARK. The analysis is based on 10,567 photographs of 2,400 individual whales taken from 1979 to 1996. The central North Pacific stock winters in Hawai'i and migrates to discrete feeding areas in Alaska for the summer and autumn. The Cormack–Jolly–Seber (CJS) estimate of annual survival based on annual sightings in Hawai'i was 0.963 (95% confidence interval [CI]: 0.944–0.978) and the Pradel estimate was 0.963 (95% CI: 0.944–0.976), with a population rate of increase of 1.10 (95% CI: 1.03–1.16). The best survival estimate for southeastern Alaska whales, based on Barker's model, was 0.957 (95% CI: 0.943–0.967). The best survival estimate for Prince William Sound whales, also based on Barker's model, was 0.984 (95% CI: 0.954–0.995). Whales from the central North Pacific stock mix in Hawai'i; therefore, the best apparent survival estimate for the entire stock is from the pooled Hawai'i data. However, this analysis also demonstrated that we could reduce heterogeneity with Barker's model and obtain more plausible estimates of survival for the whales in discrete feeding areas using semiannual sightings in Hawai'i as opportunistic resightings.