Chinook Salmon

Because it is the largest of the Pacific salmon by a wide margin. An average adult Chinook outweighs an average sockeye or coho several times over, and the biggest Chinook, the "tyee" of British Columbia lore, weigh 20 to 30 kilograms, with the rod-caught record from the Kenai River in Alaska at about 44 kilograms and a netted fish from 1949 recorded near 57. That size, together with the richness of its flesh, which has the highest fat content of any salmon, makes it the most prized species commercially and for sport, and "king salmon" is the standard market name in much of the United States.

When Chinook and other salmon return from years of feeding in the ocean, their bodies are built largely from marine-derived nutrients, especially nitrogen. They swim far up rivers, spawn, and die in enormous numbers, and their carcasses are dragged into the forest by bears and eagles, break down in the water, and are eaten by scavengers and insects. Studies using nitrogen isotopes have traced this ocean nitrogen into streamside soils, into the leaves and wood of conifers, and into the animals that eat those trees, sometimes many kilometres inland. In salmon rivers, a measurable share of the nitrogen in the forest came from the sea, delivered by fish.

The Southern Resident killer whales, a population of about 75 individuals that ranges the inland waters of Washington State and British Columbia, are fish-eating specialists, and roughly 80 percent or more of their diet through much of the year is Chinook salmon, the large, fatty fish being worth the effort to hunt. When Chinook runs are weak, the whales go hungry, lose body condition, and have fewer successful pregnancies. Their listing as endangered, and much of the recovery planning for them, is therefore focused on rebuilding Chinook runs, which links the fate of an ocean predator directly to the state of the rivers.

Salmon are not one uniform stock but a mosaic of many locally adapted populations, each returning to its own river and each tuned to that river's flow, temperature, and timing. Across the whole North Pacific there are still large, healthy Chinook runs, particularly in Alaska, so the species overall is secure. But in the more southern and heavily developed parts of the range, individual populations have been hammered by dams that block spawning grounds, by logging and farming that silt and warm the streams, by water diversion, and by decades of reliance on hatcheries that can weaken wild fitness. Some of these runs are down to a few percent of their historical size and are listed as Threatened or Endangered even while the species as a whole is not.