chum salmon

chum salmon (Oncorhynchus keta) is a species of anadromous fish in the salmon family. It is the most widely distributed of the Pacific salmon and is known for its distinctive spawning coloration. The species is commercially important across the North Pacific Ocean and holds significant cultural value for Indigenous peoples of the Pacific Northwest Coast.

Description and identification

Adult chum salmon in the ocean display a metallic blue-green coloration on the back with silver sides, closely resembling other Pacific salmon like the coho salmon and chinook salmon. Upon entering freshwater to spawn, males develop pronounced hooked jaws and large, sharp teeth, while both sexes exhibit dramatic vertical bars of green and purple, earning them the nickname "calico salmon." They can be distinguished from the sockeye salmon by the absence of spots on the back and tail and from the pink salmon by their larger size and finer scales. The species is one of the largest of the genus, second in size only to the chinook salmon, with individuals commonly reaching lengths over 90 centimeters.

Distribution and habitat

Chum salmon have the broadest natural range of any Pacific salmon, spanning the North Pacific Ocean from San Diego in the south to the Mackenzie River in Canada's Arctic and across to Hokkaido and the Sea of Okhotsk in Asia. Major spawning rivers include the Yukon River, the Amur River, and systems throughout British Columbia and Washington. They primarily utilize lower river reaches and tributaries close to the ocean for spawning, often selecting sites with substantial groundwater upwelling. Their marine phase is spent in the open ocean, with distribution influenced by currents like the Alaska Current and the Oyashio Current.

Life cycle and reproduction

The life cycle begins when adults return to their natal streams, with timing varying between summer and late fall runs. Females use their tails to create redds in gravel, where they deposit thousands of eggs that are fertilized by a guarding male. After spawning, as with most Pacific salmon, the adults die. The eggs incubate in the gravel over the winter, and the alevin emerge in the spring. Juvenile chum salmon migrate to estuarine and marine environments almost immediately, with a much shorter freshwater residency than sockeye salmon or chinook salmon. They spend two to five years maturing in the ocean before undertaking the homing migration, navigating using the Earth's magnetic field and olfactory cues.

Fisheries and human use

Chum salmon support major commercial fisheries in the United States, Russia, Japan, and Canada, with significant harvests in Alaska's Bristol Bay and the Gulf of Alaska. The catch is often processed for canned product, but a high yield of roe for ikura (salmon caviar) makes it particularly valuable in markets like Japan and South Korea. Historically, the species was a staple food for Coastal Indigenous peoples, preserved through drying and smoking. Modern fisheries are managed under agreements like the Pacific Salmon Treaty and by bodies such as the North Pacific Anadromous Fish Commission.

Conservation status

The International Union for Conservation of Nature lists the chum salmon as a species of Least Concern globally due to its wide distribution and large population. However, numerous distinct regional populations, particularly in the southern parts of its range like Puget Sound and the Columbia River, have experienced significant declines and are listed as threatened under the U.S. Endangered Species Act. Primary threats include habitat degradation from urbanization, agricultural runoff, and the construction of dams like those on the Snake River. Climate change impacts, such as warming river temperatures and altered ocean conditions, pose increasing risks to future recruitment and survival.

Category:Fish of the Pacific Ocean Category:Commercial fish Category:Fauna of the Arctic