Courtesy of Center for Whale Research

In the Pacific Northwest, we have three such “ecotypes” that don’t interact or interbreed with one another: shark-eating offshores, marine mammal-eating transients, and fish-eating residents. One population of resident killer whales, known as the Southern Residents, frequent the inland waters of Washington State and British Columbia (an area known as the Salish Sea during the summer months (May-September). The Southern Residents were listed as endangered in both Canada (2001) and the United States (2005), with three main risk factors identified: prey availability, toxins, and vessel effects.

Threats to Wild Orcas

“80-90% of the Chinook salmon the Southern Residents consumed in inland waters were from the Fraser River or its tributaries.”

study conducted by the Northwest Fisheries Science Center from 2004-2008 focused on the summer diet of Southern Residents. They collected scale samples from predation events as well as fecal samples that allowed them to determine what the whales had been eating. Using a newly developed coast-wide genetic database for salmon stocks from individual streams and rivers, they were able to determine that 80-90% of the Chinook salmon the Southern Residents consumed in inland waters were from the Fraser River or its tributaries. With headwaters in central British Columbia, the Fraser River flows over 800 miles to its output into the Strait of Georgia near the city of Vancouver. It is one of the largest salmon producing rivers in the world, but the salmon stocks that return to this river are only a fraction of their historical numbers. Similarly, the salmon of the Columbia and Sacramento Rivers, which are likely candidates for producing the salmon stocks the Southern Residents are feeding on during the winter months, have also been severely depleted.

The fish-eating Southern Resident killer whales eat almost exclusively salmon, and during the summer months (May-September) preferentially feed specifically Chinook salmon – this one species makes up more than 90% of their summer diet. The largest and fattiest of the six local salmonid species, Chinook likely provide the whales with the “most bang for their buck” when hunting. At different times of year, the whales will also consume steelhead, chum, and coho, but prey studies have shown they rarely eat sockeye and almost never eat the smallest of the bunch, pink salmon. A little less is known both about where the whales are and what they’re eating during the winter months, but in recent years more information is emerging. It shows the whales are traveling from October-April in the Pacific Ocean from British Columbia to central California, and they are still eating salmon. While other species play a somewhat larger role than during the summer, Chinook is still the predominant prey item.

In recent years, we’ve been seeing some differences in behavior among the Southern Residents. The three pods (J-, K-, and L-Pods) that make up the community have been splitting up, traveling in much smaller groups than previously. The whales are also spending less time in inland waters. During 2013, which was an especially low Chinook salmon year for the Fraser River, the whales were scarce in inland waters over the summer months, when usually they can be seen on an almost daily basis somewhere in the region. Additionally, as spring Fraser runs have declined since 2007, the whales have shifted to spending hardly any time here in the months of April and May.

A shared fate.

The issues that plague our major salmon-producing rivers include dams that block salmon from their natal spawning grounds, historical and current overfishing that have kept healthy numbers of adult salmon from spawning, habitat degradation that has made streams unhealthy places for juvenile salmon, and fish farming – salmon feedlots that wild salmon swim through that are hotbeds of disease.

It’s not uncommon to read about “record” salmon returns to some of our regional rivers, but it’s important to keep these reports in perspective. Salmon numbers seem especially subject to a phenomenon known as “shifting baselines”, where numbers are compared to more recent reference points rather than to even earlier data. For salmon returns, this means we may experience a high return compared to any other return in the last 20 years, but it’s important to remember that even 40 years ago salmon numbers were down drastically from historic numbers. These historic numbers often aren’t referenced in the media, making it seem like things are going just fine for our rivers, when in fact they’re still producing only a fraction of the salmon that they used to.

Salmon live an amazing life cycle that takes them from freshwater streams, where they hatch, down river corridors and through estuaries where they grow, and out saltwater straits into the open ocean where they spend 2-4 years becoming adults before reversing the whole cycle and returning to the same place from which they were born to spawn. Think of the salmon’s life cycle as taking them through a chain of habitats, and like any chain, it is only as strong as its weakest link. If there is a problem in the streams, in the estuaries, in the nearshore coastal waters, or out in the open ocean, the salmon will be effected and will not thrive.

Courtesy of Center for Whale Research

More than 100 species, including humans, consume salmon. Additionally, ocean nutrients are transferred to our forests through spawned out salmon carcasses, further demonstrating how salmon are truly the lifeblood of our Pacific Northwest ecosystems. While it is a worthy cause to protect the salmon and the orcas for their own sake, the local killer whales also serve as an indicator species for the health of our whole region. If they aren’t healthy, neither is our ecosystem, and that is an even greater cause for concern.

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