Chum Salmon

Chum Salmon, also known as dog salmon, one of five Pacific salmon species. Like many members of the trout and salmon family, chum are anadromous—they hatch in freshwater, then migrate to the ocean. Chum salmon spend three to five years at sea before returning to their native streams to lay their eggs, or spawn, then die.

Chum salmon range along the west coast of North America from southern California to northern Alaska, and west across the Pacific Ocean to Japan.

Mature chum usually weigh 4.4 to 6.6 kg (9.7 to 14.6 lb) and average 60 cm (24 in) in length, although chum as large as 13 kg (30 lb) and 102 cm (40 in) have been recorded. At sea, chum have steel-blue upper bodies and silver bellies. As they approach freshwater to spawn, their coloration changes to shimmering reds, browns, and greens. In preparation for fighting over females, males develop a humped back and a very exaggerated upper jaw with prominent doglike teeth. Spawning females develop slightly less prominent jaws than males, and their abdomens swell with 5000 developing eggs.

Juvenile chum feed by sifting plankton from the water as it passes through their gills. When chum salmon return to freshwater as adults, they stop feeding altogether, gradually starving until they die roughly two weeks after spawning.

Most chum salmon spawn in estuaries, the shallow, protected waters where rivers meet the ocean. A female digs a nest, called a redd, by turning over on her side and vigorously digging in the streambed with her powerful tail. Once the female is ready she lays her eggs in the nest. Males fight with each other over the chance to spawn with a female, and the victorious male sprays milt (sperm) over the eggs in the nest. The female then covers the eggs with additional gravel to protect them and then leaves them to hatch on their own.

Chum are the least commercially valuable member of the Pacific salmon fishery. In Alaska, chum salmon are so numerous that low prices often keep commercial fishers from trying to catch them. But like most salmon, few wild chum populations remain healthy in the southern part of their range, where they are threatened by destruction of spawning habitat. When the land around rivers is developed or logged, the resulting eroded soil clogs gravel streambeds, making them unsuitable for spawning. Dams and other river diversions that block fish passage also threaten chum survival.

Scientific classification: The chum salmon is a member of the family Salmonidae in the Salmoniformes order. It is classified as Oncorhynchus keta.