They’re a type, or ecotype, of killer whale that eats fish. Although there are an estimated 50,000 killer whales around the world, there are many different populations and ecotypes. These populations and ecotypes don’t mingle. They look different, they sound different and they eat different things.

In the Salish Sea we regularly see two killer whale ecotypes. There are Bigg’s (also known as transients) which eat marine mammals. And there are the southern residents which eat fish. Bigg’s killer whales are thriving. The southern residents are not and are listed as endangered in both Canada and the US. They’re at very high risk of extinction. There are only 73 of them left.

Their traditional core habitat in the summer and fall is the Salish Sea. This is where they follow various salmon runs as the fish return to their spawning rivers. The Fraser River in BC and the Columbia River in the US are two salmon river systems that are very important to them.

In the winter, the southern residents spend more time on the outer coast. They’ve been seen as far south as Monterey, California, and as far north as southeast Alaska. In recent summers, they’ve been spending much less time in the Salish Sea. That’s because their preferred food simply isn’t here anymore. Wherever they are, we hope they’re finding the food they need.

The reasons are many and complex. Most if not all of them, are related to human activity. Until the 1960s, killer whales were seen as competitors for fish and were often shot on sight. From 1965 to 1975, 50 southern residents—mainly young whales—were captured for the marine park industry. At least 12 others were killed in the process. This removed almost an entire generation from the population.

Other ongoing factors include chronic overfishing, chemical contaminants, and shipping and noise disturbance. But by far the main problem facing these whales is the decline of their #1 food choice—chinook salmon.

At least 80% of their annual diet is chinook. At certain times of the year they also target chum and coho salmon. An adult southern resident killer whale needs to consume up to 25 adult salmon daily just to meet its energy requirements. In other words, the entire population needs at least 1,400 good-sized salmon every day. That’s half a million salmon a year.

This dependence on chinook is very obvious. Studies conducted over decades show that when chinook numbers go down, resident killer whale mortality goes up. Chronic malnutrition also makes the whales vulnerable to disease, infection, reproductive failure and environmental toxins.

Chinook—also known as springs, kings, tyees or blackmouths—are the largest and fattiest of the seven species of salmonid fish in the Pacific Northwest. They can weigh over 100 lb., although those giants have all but disappeared due to heavy commercial fishing pressure. The average size of a chinook salmon these days is 30 lb. This means the whales have to work harder to catch more fish to meet their daily needs.

It makes sense that resident killer whales evolved to depend on chinook. Why waste your energy chasing more abundant but smaller and less fatty fish when you can satisfy your needs with a few big, fat chinook? Also, because different chinook runs return to their spawning rivers at different times of the year, the whales have a year-round food supply. Or they should, in a healthy marine ecosystem.

Coastwide, wild chinook salmon have declined over decades from millions of fish a year to thousands. Some populations are already extinct. Many others are endangered.

The chinook story is a classic example of death by a thousand cuts. We’ve overharvested them. We’ve blocked some of their spawning rivers with dams and roads. We destroy or degrade their spawning or estuarine habitats. We introduce hatchery-raised fish as competitors. We catch important food sources such as herring for ourselves. On top of all this, climate change is altering marine ecosystems and warming rivers, affecting ocean survival and spawning success.

One word: culture. While there’s nothing to prevent a southern resident from grabbing a harbour seal and eating it, there are strong cultural barriers against it. Killer whales are intelligent, social animals. Each population around the world has evolved over millennia with a set of learned behaviours and customs. These are passed down through generations.

What to eat and how to hunt it is one of these cultural traditions. Chinook salmon are central to resident killer whale culture. Switching to a diet of marine mammals is unlikely. It would require learning a set of completely different hunting skills. Over time, the southern residents might adapt to eating other types of fish. But the current rate of change is too rapid for them. They don’t have the time to create a new hunting culture.

Watch a short video about killer whale culture!

Salmon play a big part in the ecology, culture and economy of the Pacific Northwest. At least 138 species—from whales to bears, birds and insects—rely on salmon for their food in some way. Even the health of coastal forests depend on salmon.

Salmon are also deeply embedded in the culture, spirituality and identity of Indigenous peoples in the Pacific Northwest. And salmon are key economic drivers, greatly valued by the commercial and sportfishing industries.

The southern resident killer whales are beloved emblems of the Salish Sea. They are culturally and genetically unique. If we lose them, their entire gene pool and all the unique knowledge, behaviours and adaptations accumulated over millennia will be gone forever. And it will be our fault. Which means it’s our responsibility to make sure that doesn’t happen!

Learn more about southern resident killer whales and salmon.