ANACORTES, Wash. (CN) – Decades of politics and foot-dragging have stymied the recovery of threatened and endangered Chinook salmon, while an iconic population of killer whales that depends on them veered toward extinction. Now, a last-ditch effort to save the whales may also be what thwarts the recovery of Chinook.
The Southern Resident killer whales are dying. An extended family of 75 orcas living year-round in the sea surrounding the San Juan Islands near Seattle, their numbers never fully rebounded since aquariums that later became SeaWorld captured a third of them in the late 1960s.
And there are other culprits.
Cargo ships and whale-watching boats zip through the Salish Sea, adding noise that interferes with the whales’ ability to locate each other and their prey. The water they live in is toxic. The Puget Sound outside Seattle is tainted with flame retardant, and PCBs and pollutants gush from nearby rivers into the sea.
The Chinook salmon they eat to live are contaminated with mercury, lead and organic compounds like PCBs. The Washington state Department of Health advises humans to limit their consumption of Chinook salmon to eight ounces per week. But Southern Residents eat dozens of the fish per day.
Not only is their food toxic, there’s also less of it than ever before. Five populations of Chinook the whales depend on are listed as threatened; a sixth is endangered. And they’re smaller, declining in size by 10 percent since the late 1970s, according to research published February in the scientific journal Fish & Fisheries.
But while the Southern Resident whales struggle to survive, similar populations of orca thrive despite many of the same pressures. Northern Resident killer whales in the waters around Vancouver, British Columbia, flourish. They eat Chinook, just like Southern Residents. But their population has more than doubled since tracking began in the 1970s – up to 309 in 2017.
Transient orca pods, which migrate between the Salish Sea and the open Pacific Ocean, eat marine mammals like seals. They now number over 500, which wildlife managers say may be close to the maximum their habitat can support. And the populations of seals and sea lions have dramatically rebounded since the 1970s – though they are just as toxic as salmon.
Ken Balcomb, senior scientist with the Center for Whale Research, says the main problem is that the Southern Residents have so little prey to eat they have to survive on their fat stores, where the toxicity concentrates.
“Transients are still doing great,” Balcomb said. “They’re cranking out babies at six percent because they have a lot of food. They don’t have to draw on their fat because they have plenty to eat.”
The problem is especially apparent, according to Balcomb, when the orcas can’t find enough salmon during pregnancy. If a pregnant whale draws from her toxic fat stores to feed her growing fetus, the offspring will likely be born with significant problems like immunosuppression akin to HIV or an underdeveloped nervous system.
Female Southern Residents used to produce about five calves in their lifetimes. Now they are lucky to have two. They routinely miscarry or deliver calves that soon die. Those that survive never develop functioning reproductive systems.
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