A variety of fish and birds prey on juvenile chum salmon.
Adults eat copepods, fish, mollusks, squid, and tunicates. Young salmon feed on insects and marine invertebrates as they migrate downriver and into estuaries and near-shore habitats. Unlike other salmon species, chum salmon fry do not spend an extended period of time in freshwater and begin migrating back to estuarine and marine waters a few days after they are born. The carcasses are known to be a valuable source of energy and nutrients to the river ecosystem, improving newly hatched salmon growth and survival by contributing nitrogen and phosphorous compounds to the water. Females dig out gravel nests called redds on stream bottoms to lay their eggs, laying about 2000-4000. Chum salmon nest near the mouth of rivers, about 60 miles (97 km) from the ocean because of their large size and limited jumping ability to move farther upstream into shallower waters. Peak spawning season is in the early winter when the river is high. They reach maturity between ages three and six. Before the juveniles migrate to the sea, they lose their parr marks for a dark back and light belly.Ĭhum salmon grow up to 3.6 feet (1.5 meters) in length and weigh 30 to 35 pounds however, most are caught averaging between eight to 15 pounds. Freshwater fry entering the parr stage have well-developed camouflaging stripes along their sides. Males develop canine fangs and a hooked upper jaw. In freshwater, both sexes develop a red and black tiger-striped pattern. In the ocean, they are a metallic blue-green along the back, with black specks, similar to sockeye and coho salmon.
Like other salmon species, chum salmon are anadromous, meaning they hatch in freshwater streams and rivers, then migrate to saltwater environments to feed and grow. Chum salmon are the second largest of the Pacific salmon, behind only Chinook salmon in size.
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