Environmental Matters in the Commonwealth of Kentucky

Chinook salmon are easily the largest of any salmon, with adults often exceeding 40 pounds (18 kg); individuals over 120 pounds (54 kg) have been reported. Chinook mature at about 36 inches and 30 pounds.  Chinook salmon are very similar to coho salmon in appearance while at sea (blue-green back with silver flanks), except for their large size, small black spots on both lobes of the tail, and black pigment along the base of the teeth.  Chinook salmon may spend between 1 to 8 years in the ocean before returning to their natal streams to spawn, though the average is 3 to 4 years. 

Chinook salmon are exceptionally beautiful fish, especially when they break the water and their scales shin in the sunlight.  Chinook are game fighting sport fish.  Once you have landed your Chinook, you are truly hooked on the sport.  Salmon fishing is a huge business in the Northwest, especially in smaller communities located near rivers with salmon runs.  A lot of these folks depend on money spent by sport fishermen during the fall and spring salmon runs to economically survive each year.

Adult Chinook salmon migrate from the ocean into freshwater streams and rivers of their birth in order to mate.  This behavior is called anadromy.  Salmon spawn only once and then die, which is called semelparity.  Because of their remarkable life cycle and reproduction behavior, once Chinook salmon stop breeding in a specific river or tributary, they are normally lost forever.

Unfortunately, this year Chinook salmon are the conservation heartbreak of the U.S. West Coast.  Chinook salmon have almost disappeared from the Sacramento River in Northern California and left depressed fisheries experts struggling for a plausible explanation.  In Oregon where Chinook season is truly a religion-like experience, fishery managers closed sport fishing for spring Chinook in the Willamette River and tributaries above Willamette Falls on June 2.  It is a huge economic loss for everyone.

But it seems that all may not be lost at least in the bigger picture.  Chinook salmon are thriving in the southern part of South America, albeit as an invasive species. Chinook salmon reached South America some 25 years ago as people tried to farm them there, says Cristián Correa of McGill University in Montreal. Now a broad survey of records and stream visits finds Chinook reproducing on their own in at least 10 Andean watersheds that empty into the Pacific plus more along the coast, and three Atlantic watersheds, Correa and Mart Gross of the University of Toronto report in the June Biological Invasions.

According to the two biologists, the Chinook’s invasion of South America began about 25 years ago.  They hypothesize that salmon farming operations used spring-run Chinook salmon originally taken from tributaries of the lower Columbia River. The rapid spread suggests that Chinook salmon were pre-adapted to their new ocean and freshwater environments because of similarities to their ancestors’ North Pacific habitats.  In addition, Chinook face low resistance from native fish in their South American habitat. Thus, Chinook populations are growing in South American while salmon runs in California, Oregon and Washington are declining.