Trends in the Abundance of Humpback Whales in the North Pacific Ocean from 1980 to 2006

We examine long terms trends in abundance of humpback whales in the North Pacific overall and in specific regions based on data from SPLASH (a comprehensive collaborative study conducted 2004-06) and datasets from previous time periods incorporating several approaches to adjust for differences in sampling. The trends for the entire North Pacific Ocean were based on comparison of the overall abundance from two basin-wide studies conducted in 1990-93 and 2004-2006. These showed an increase from approximately 11,300, to 22,600 animals based on subsampling the more comprehensive 2004-2006 data to be similarly biased to the earlier study (5.5% per year over 13 years). A similar comparison but using all data and correcting for bias showed an increase from 9,500 to 21,063 in the same period or an increase of 6.3% per year. Trends for winter breeding regions in Hawaii and Mexico and feeding areas off the US West Coast (California and Oregon) and in SE Alaska were conducted with either interyear or inter-regional mark-recapture estimates; these all showed rates of increase of 5 to 8% per year with the rates for US West Coast feeding areas and Mexico significantly higher than for Hawaii. Our results are consistent with a population that was reduced to low levels due to commercial whaling which occurred through 1966 and which has been recovering since then and, as of 2006, had not yet reached carrying capacity.

Citation:

Calambokidis, J., and J. Barlow. 2017. Trends in the Abundance of Humpback Whales in the North Pacific Ocean from 1980 to 2006. IWC Report SC/A17/NP/10 for the Workshop on the Comprehensive Assessment of North Pacific Humpback Whales. 18-21 April 2017. Seattle, WA. 16pp.