Researchers in 10 countries collaborated to measure the number of humpback whales in the North Pacific. They relied on photographs of whale flukes, as each is unique, to track sightings of whales and to estimate populations. They estimated that there were just under 20,000 humpback whales in the North Pacific in 2008; this is a notable increase from the 1,400 humpback whales in the region in 1966, when whaling was banned.

From the executive summary of the report:

“SPLASH (Structure of Populations, Levels of Abundance and Status of Humpbacks) represents one of the largest international collaborative studies of any whale population ever conducted. It was designed to determine the abundance, trends, movements, and population structure of humpback whales throughout the North Pacific and to examine human impacts on this population.”

“Using several methods, the abundance of humpback whales was estimated to be just under 20,000 for the entire North Pacific, an estimate that is about double estimates made previously. …18,302 represented the best estimate of overall abundance of humpback whales in the North Pacific, excluding calves. Over 50% of this population was estimated to winter in Hawaiian waters with large populations also inhabiting Mexican waters.

The abundance estimates of humpback whales wintering in Asia and Central America were fairly low (1,000 or less). Among feeding areas, regional estimates differed greatly among models.

Average estimates of abundance ranged from about 100-700 for Russia, 6,000-14,000 for the Bering Sea and Aleutians, 3,000-5,000 each for the Gulf of Alaska and the combined Southeast Alaska and Northern British Columbia area, 200-400 for Southern British Columbia-Northern Washington, and 1,400-1,700 for California-Oregon.”

“The SPLASH estimate represents a dramatic increase in abundance from other postwhaling estimates for the overall North Pacific, yet is consistent with a moderate rate of recovery for a depleted population. Comparison of the SPLASH estimate of 18,302 for all feeding and wintering areas to the estimate of 9,819 obtained for 1991-93 in a previous study suggests a 4.9% annual increase over this 13-year period. Going back to the estimate of 1,400 whales at the end of whaling for humpbacks in 1966, a 6.8% annual increase over the 39-year period would be required to reach the current SPLASH abundance. For Hawaii, three methods were used to compare estimates to determine trends since the early 1990s and yielded very similar annual rate of increase from 5.5 to 6.0%.”

The link below will begin a download of a PDF version of the full report.