Pacific Northwest Orca Population Hits 30-Year-Low

Killer whales are one of the iconic sights of the Pacific Northwest, but future generations may not have the chance to appreciate them. Their population has just hit a 30-year low, according to an annual census.

The Southern Resident killer whale population is just one population of the black-and-white whales, which worldwide are estimated to number in the tens of thousands. But the southern resident whales, whose numbers hover below 100, are considered endangered by the U.S. Fish and Wildlife Service.

According to the annual census, the whales' situation is more dire than ever: No calves have been born over the past three years, and the current population is only 75.

The New York Times’ Jim Robbins reports that under normal circumstances, four or five calves would be born each year. In 2015, the Seattle Post-Intelligencer’s Zosha Millman adds, nine calves were born, although three, including one named Sonic, have since died.

Robbins writes that the whales are “essentially starving” as their main food source, the Chinook salmon, experiences a decline in population. Orcas typically eat 30 of these 40-inch-long fish per day, but shrinking numbers have forced the whales to expend more energy hunting smaller prey.

The salmon itself poses a threat to the whales, as chemicals and pesticides accumulate as the fish feed and eventually end up stored in the orcas’ fat. These toxins suppress the whales' immune systems, leaving them vulnerable to disease, and can affect the females' ability to reproduce.

An additional cause for concern is the planned 600-mile expansion of the TransMountain Pipeline, which runs through the orcas’ habitat and is expected to multiply the number of oil tankers in the area by a factor of seven. When construction begins in August, excessive noise and potential oil spills will add to existing threats posed by noise and boat traffic, according to Lynda V. Mapes of the Seattle Times.

Although declining salmon numbers, pollution and noise disturbance pose the most immediate threats to the whales' survival, Millman reports that other factors may be at play. Scientists are rarely able to test dead orcas, as their bodies sink or wash up in remote areas, so much of their plight remains unknown. Robbins writes that anthroponeses, or diseases passed from humans to animals, are one concern: Orcas are consistently exposed to airborne pathogens that their immune systems may not equipped to fend off.

"If there were a highly virulent virus to come through here it would take out a large part of the population and totally stop recovery efforts," orca researcher Joseph K. Gaydos tells Robbins.

Another potential explanation is overarching issues within the mammals' ecosytem. As Robbins notes, a mass of extremely warm water known as "The Blob" has raised water temperatures across the Pacific by as much as six degrees.

Southern Resident whales are typically spotted around the Salish Sea, an inland body of water that connects British Columbia to Washington’s Puget Sound. Their migration pattern follows that of the Chinook salmon, Millman notes, but has become more erratic with changes in the salmon population.

The sharp decline in the killer whale population has sparked numerous conservation efforts, including a March executive order signed by Washington Governor Jay Inslee directing state agencies to find ways to support the whales (proposed solutions include decreased boat traffic, improved clean-up of toxins and renewed efforts to revitalize the Chinook salmon population), and an increase in studies designed to pinpoint the sources of these rising mortality rates.

“The orca will not survive unless all of us in the state of Washington somehow make a commitment to their survival," Inslee said when signing the order. Speaking of both the whales and the Chinook salmon, he said, "the impacts of letting these two species disappear would be felt for generations."

Meilan Solly | | READ MORE

Meilan Solly is Smithsonian magazine's senior associate digital editor, history.