Category: Status Reports
Published: April 2016
Revised: June 2016
Author(s): Gary J. Wiles
Killer whales have been listed as a state endangered species in Washington since 2004. Three main populations known as the southern residents, west coast transients, and offshores occur in the state. While closely similar in appearance, these ecotypes differ in their biology, rarely interact with one another, and do not interbreed despite having largely sympatric year-round distributions ranging from California to Alaska. All three populations make extensive use of Washington's outer coastal waters, with the southern residents and transients also regularly visiting the Salish Sea. Southern resident killer whales prey primarily on chinook salmon, with chum and coho salmon also consumed during certain seasons, west coast transient whales feed primarily on harbor seals and other marine mammals, and offshore killer whales appear to prey mainly on sharks.
Southern residents totaled just 81 whales as of July 2015 and are the population of greatest concern. Numbers have been relatively stable since 2001, but remain 17% below their recent peak size recorded in 1995. In addition, the population's growth rate remains well below the downlisting and delisting goals established in the 2008 federal recovery plan. The recent lack of significant growth in the population also contrasts greatly with the continuing growth of two similar resident populations in British Columbia and Alaska, which have expanded at average annual rates of 2.9% and 3.5% in recent decades. The southern resident population faces significant potential threats from the reduced availability of chinook salmon, interactions with whale-watching vessels and human generated marine sound, and factors associated with its small population size, including the recent skewing of births towards males, which will constrain productivity over the next few decades.
In contrast, the west coast transient population has shown considerable growth since the 1970s in response to the recovery of its marine mammal prey base, and is now estimated to number more than 500 whales and be near its carrying capacity. Offshore killer whales are estimated at 300 individuals and have a stable population trend. All three populations carry heavy loads of environmental contaminants, face a continuing risk of major oil spills in their ranges, are susceptible to a disease outbreak, and will likely experience the impacts of climate change in the future.
Various management activities have been taken since 2004 that directly or indirectly benefit killer whales in Washington, many of which are aimed at the southern residents. These include the preparation of conservation plans; designation of federal critical habitat for southern residents; implementation and enforcement of new whale-watching regulations; evaluation of chinook salmon abundance and marine fisheries on the southern residents; population monitoring; research; public outreach; salmon management and recovery; steps to enhance oil spill prevention and response, and to deter whales away from spills; and measures to reduce the input of environmental contaminants into marine waters. Nevertheless, expanded actions will very likely be needed to achieve recovery of the southern residents.
For these reasons, it is recommended that killer whales remain listed as a state endangered species in Washington. The protections associated with this listing apply to all populations of killer whale occurring in the state.
Draft documents are provided for informational purposes only. Drafts may contain factual inaccuracies and may not reflect current WDFW policy.