Two of these ESUs, Hood Canal summer-run and Columbia River, were proposed as threatened under the ESA in March 1998. Species Biology Chum salmon belong to the family Salmonidae and are one of eight species of Pacific salmonids in the genus Oncorhynchus . Chum salmon grow to be among the largest of Pacific salmon, second only to chinook salmon in adult size, with individuals reported up to 108.9 cm in length and 20.8 kg in weight. Average size for the species is around 3.6 to 6.8 kg.
Females are less flamboyantly colored and lack the extreme dentition of the males.
Chum salmon may historically have been the most abundant of all salmonids. Chum salmon spawn in the lowermost reaches of rivers and streams, typically within 100 km of the ocean. They migrate almost immediately after hatching to estuarine and ocean waters, in contrast to coho, chinook, sockeye and pink salmon, and steelhead and cutthroat trout, which migrate to sea after months or even years in fresh water. Another behavioral difference between chum salmon and most species that rear extensively in fresh water is that chum salmon form schools, presumably to reduce predation. Age at maturity appears to follow a latitudinal trend in which a greater number of older fish occur in the northern portion of the species range.