Chinook salmon swim over 3,000 kilometres up the Yukon to spawn
The largest of the Pacific salmon can top 59 kilograms, and some make astonishing journeys home. Yukon River Chinook travel more than 3,000 kilometres from the Bering Sea to spawning grounds beyond Whitehorse, the longest freshwater run of any salmon, fuelled entirely by fat stored at sea.
Native to rivers from California to Alaska and from northern Japan to Arctic Siberia, Chinook are also called king, spring or tyee salmon; the scientific name comes from the Russian word chavycha. They hatch in fresh water, spend one to eight years at sea, usually three or four, then return to their home rivers. Idaho fish climb more than 2,100 metres in elevation and pass eight dams on the Columbia and Snake Rivers to reach the Salmon River headwaters.
Spawning transforms them. The silvery ocean colour darkens, and males grow canine-like teeth and a hooked jaw called a kype. Females dig nests in deeper, gravellier water than other salmon use, lay eggs in several pockets, and guard them for four to 25 days before dying. Eggs hatch after 90 to 150 days, depending on temperature. Some males, called jacks, come home a year or two early, sexually mature but under 60 centimetres long.
People have moved them around the world. Michigan stocked Lake Michigan and Lake Huron in 1967 to eat alewives, invasive Atlantic fish that made up 90 percent of the lakes' life in the 1960s; the salmon thrived, but still depend on yearly restocking. In New Zealand, early attempts failed until eggs from autumn-run fish were used, and a single release in Patagonia around 1930 produced salmon that now swim over 1,000 kilometres up the Rio Santa Cruz.
At home they are in trouble in many places. Dams and habitat changes have cut off inland ranges, some populations have shrunk by as much as 40 percent, and in California's Sacramento–San Joaquin Delta fewer than 1 percent of juveniles were found to survive. The giant summer fish of the Pacific Northwest, once nicknamed June hogs, are now rare.
Source: Chinook salmon
