Periodic Status Review for the Humpback Whale in Washington (Mar 2021)

The humpback whale is a large baleen whale found in nearly all of the world’s oceans that forages on zooplankton and small fish primarily in continental shelf waters. The species undertakes long distance migrations between winter breeding grounds in tropical and subtropical waters and summer feeding grounds in high-latitude waters.

Like other large whales, humpback whales were heavily exploited worldwide by the whaling industry, including in Washington. Populations in the North Pacific were roughly estimated at 15,000 animals prior to commercial harvest. By the time the species received global protection in 1966, North Pacific populations were severely depleted, with estimates of only 1,200 to 1,400 individuals remaining. Since that time, these populations have rebounded to an estimated 16,000 to 21,000 animals, although some stocks have recovered more successfully than others.

Humpback whales have been listed as a state endangered species in Washington since 1981. In 2016, the National Marine Fisheries Service revised the federal Endangered Species Act listing for the humpback whale to identify 14 Distinct Population Segments (DPSs) worldwide, three of which visit Washington’s waters. These include (1) the Mexico DPS, which comprises 27.9 percent of humpback whales present in the state and is federally threatened, (2) the Central America DPS, which contributes the fewest animals (8.7 percent) among Washington’s humpbacks and is federally endangered, and (3) the Hawaii DPS, which comprises 63.5 percent of the humpbacks visiting Washington and is not federally listed.

Humpback whales in the North Pacific remain vulnerable to a number of threats, including entanglement in fishing gear and marine debris, ship strikes, human-generated marine sound, the effects of climate change, and for the Central America DPS, possible issues related to small population size.

Humpback whales as a species have rebounded since the cessation of whaling activity in the mid-20th century. However, the Central America DPS and the Mexico DPS, which together comprise 36.6 percent of the humpback whales that visit Washington waters, remain below sustainable numbers and continue to be federally listed as endangered and threatened, respectively. Due to their federal status and the threats and uncertainties described in this report, it is recommended that this species be retained as a state endangered species in Washington.