The chum salmon (Oncorhynchus keta) is a species of anadromous fish in the salmon family. It is a Pacific salmon, and may also be known as dog salmon or keta salmon, and is often marketed under the name silverbrite salmon. The name chum salmon comes from the Chinook Jargon term tzum, meaning "spotted" or "marked", while keta in the scientific name comes from the Evenki language of Eastern Siberia via Russian.
The body of the chum salmon is deeper than most salmonid species. In common with other species found in the Pacific, the anal fin has 12 to 20 rays, compared with a maximum of 12 in European species. Chum have an ocean coloration of silvery blue green with some indistinct spotting in a darker shade, and a rather paler belly. When they move into fresh water the color changes to dark olive green and the belly color deepens. When adults are near spawning, they have purple blotchy streaks near the caudal peduncle, darker towards the tail. Spawning males typically grow an elongated snout or kype, their lower fins become tipped with white and they have enlarged teeth. Some researchers speculate these characteristics are used to compete for mates.
Most chum salmon spawn in small streams and intertidal zones. Some chum travel more than 3,200Â km (2,000Â mi) up the Yukon River. Chum fry migrate out to sea from March through July, almost immediately after becoming free swimmers. They spend one to three years traveling very long distances in the ocean. These are the last salmon to spawn (November to January) in some regions. In Alaska they are the first to spawn in June and August and are then followed by pink and coho salmon. They die about two weeks after they return to the freshwater to spawn. They utilize the lower tributaries of the watershed, tend to build nests called redds, really little more than protected depressions in the gravel, in shallow edges of the watercourse and at the tail end of deep pools. The female lays eggs in the redd, the male sprays milt on the eggs, and the female covers the eggs with gravel. The female can lay up to 4000 eggs.
Chum live for an average of 3 to 4 years, and chum in Alaska mature at the age of 4 years.
Chum salmon have the largest natural range of any Pacific salmon, and undergo the longest migrations within the genus Oncorhynchus, far up the Yukon River and deep into the Amur River basin in Asia. In lesser numbers they migrate thousands of kilometres up the Mackenzie River. Chum are found around the north Pacific, in the waters of Korea, Japan, and the Okhotsk and Bering seas (Kamchatka, Chukotka, Kuril Islands, Sakhalin, Khabarovsk Krai, Primorsky Krai), British Columbia in Canada, and from Alaska to California in the United States. In Arctic Ocean they are found in limited numbers from the Laptev Sea to the Beaufort Sea.
Adult chum usually weigh from 4.4 to 10.0Â kg, (9.7Â lbs to 22.0Â lbs) with an average length of 60Â cm (24 inches). The record for chum is 19Â kg (42Â lbs) and 112Â cm (44 inches) and was caught at Edie Pass in British Columbia.
Juvenile chum eat zooplankton and insects. Recent studies show that they also eat comb jellies. As adults, they eat smaller fish.
Commercial use and value
The registered total harvest of the chum salmon in the North Pacific in 2010 was some 313,000 tonnes, corresponding to 91 million fish. Half of the catch was from Japan, and about a quarter from Russia and the United States each. The chum salmon harvest was about 34Â % of the total harvest of all Pacific salmon species by weight.
The chum salmon is the least commercially valuable salmon in North America. Despite being extremely plentiful in Alaska, commercial fishers often choose not to fish for them because of their low market value. Recent market developments have increased the demand for Chum salmon. Markets developed for chum from 1984 to 1994 in Japan and northern Europe which increased demand. They are a traditional source of dried salmon.
Two populations of Chum have been listed under the Endangered Species Act, as threatened species. These are the Hood Canal Summer Run population and the Lower Columbia River Population.
Susceptibility to diseases
Chum are thought to be fairly resistant to whirling disease, but it is unclear.
- National Marine Fisheries Service chum salmon web page
- Froese, Rainer and Pauly, Daniel, eds. (2005). "Oncorhynchus keta" in FishBase. 10 2005 version.
- Alaska Department of Fish and Game
- National Marine Fisheries Service ESA Listings