Salmon is a vital resource in the state, so it should come as no surprise that Alaska has been studying salmon since before statehood. For over 60 years, the Alaska Department of Fish and Game has kept detailed records of length, weight, age and escapement for four species of Pacific salmon that spawn here.
The salmon that return to Alaska from their time in the ocean, are now smaller than they have been historically. The reason: They are returning to spawn at a younger age.
The Chinook, Alaska’s state fish, has been the hardest hit. King salmon are, on average, coming in at 8% smaller than in the 1980’s. The coho, or silver salmon is 3.3% smaller, chum is at 2.4%, and the sockeye 2.1. The decrease in size has accelerated since 2010 for all four species.
At first glance, what is 8% really? Well, the ramifications are large and far reaching. The Yukon-Kuskokwim River system is the largest subsistence area in the entire country. It takes more fish to feed a family. Commercial fishermen also must catch more fish to make the same amount of money.
Environmentally, the entire ecosystem relies on the salmon returning to spawn. Just the reduction in chinook salmon size alone means a reduction of 16% in egg production, i.e. future salmon populations; and a 28% reduction in nutrients going back into the river systems. For the pocket book issues: the reduction in king salmon means a 26% reduction as a food source, and a 21% reduction in the value of the fishery.
There does not appear to be one smoking gun for the change in Alaska’s salmon population, but a series of events that effect each species differently. Warming ocean temperatures are partly to blame, but so is competition between wild and hatchery populations. Size-selective fishing seems to also be a part of the equation, especially with the mighty chinook.
Wild salmon can stay out in the ocean for up to 7 years, but now they are often returning to fresh water to spawn at 4 years.
Sources: University of Alaska – Fairbanks; Alaska Dept of Fish & Game; Alaska Public Media; Fairbanks Daily News-Miner