A well-known extended family of Pacific Northwest orcas is dying off in the waters of Washington State and British Columbia. For the last three years, scientists have not recorded a single calf, resulting in a 30-year low in killer whale populations in the area.
The Southern Resident killer whale (SRKW) clan is one of two orca communities in the area. At a height of 100 members following a 1989 ban on orca capture, data provided by the Center for Whale Research and compiled by Orca Network found that the SRKW population now has just 75 members, reports the Seattle Post-Intelligencer.
Nine new orcas were born in 2015 in a "baby boom", but a recent census reported two missing and presumed dead whales: 23-year-old Crewser (L-92) and a 2-year-old calf called Sonic (J-52).
Scientists can’t say with certainty what is causing the population decline because dead orcas typically sink or wash up on remote beaches, limiting opportunities for autopsies or further research. But whale experts do have some working theories.
The endangered SRKW whales’ migration routes follow the patterns of their primary prey, the king salmon. Last year saw some of the lowest numbers of salmon returning to freshwater rivers to spawn, and this year’s forecast is much grimmer: just 50 percent of Columbia River kings are expected to return, with nearby Puget Sound fisheries down almost 40 percent. A similar trend follows all along the western coast of the US, from California to Alaska.
Researchers who study the pod also say pollution is a major contributor to the population decline. Because orcas are an apex predator, their prey accumulates pollutants that are then stored in the orcas' fat, which can make them more susceptible to diseases.
Furthermore, the SRKW family spends spring, summer, and fall in the waters of the Salish Sea, which connects Washington State to the Gulf Islands in British Columbia. This area has become a major hub for transportation as the Trans Mountain Pipeline expands, increasing the number of tankers plowing through orca territory by sevenfold and further exposing the pods to risks of pollution, boat collisions, and underwater noise.
But why they’re not reproducing remains even more of a mystery. Scientists say it could be a result of these ecosystem-wide pressures, including a confirmed steady rise in ocean temperatures over the past 75 years.
According to the Seattle P-I, Washington lawmakers are taking steps to find further ways to protect the SRKW family, including an executive order that directs state agencies to “do more”. But researchers say promises aren’t enough.
"It's an ecosystem-wide problem," Brad Hanson with the Northwest Fisheries Science Center told The New York Times. "Things are out of whack and we have to get them back to where we can sustain killer whales. And the clock is ticking."
[H/T: Seattle Post-Intelligencer]