High Altitude View
Bad News: A two to three-year episode of warm water and low ocean productivity has resulted in lower numbers of chinook (king) salmon coastwide. Southeast Alaska’s king salmon annual limit is derived in most years by the Abundance Index (AI). The AI is a complex calculation that uses all kinds of inputs that are intended to reflect coastwide chinook abundance in the current year. Based on the AI, the harvest level is set to ensure adequate numbers of returning kings to produce the next generation on the spawning grounds and in the hatcheries. The abundance index for 2018 is 1.07, which is very low and reflects the impacts of the warm water event known as “the Blob”
In 2018, a second set of inputs has impacted the Southeast Alaska harvest regulations. The returns to the transboundary (rivers that flow through Southeast Alaska into British Columbia) and Southeast Alaska mainland rivers are very depressed. Again, the reason is ocean productivity. These rivers have lots of good habitat and the outmigration of the juveniles that would form the returning generations of 2018 indicated no particular problem. But, these juveniles did not find what they needed to thrive on the open ocean. The predicted returns to these rivers are very low, thus the need for added regulations to protect of these fish.
Good News: The blob has dissipated, and the North Pacific appears to be returning to more normal temperatures and production. (see Ocean Temps Stabilize, Marine Blob Retreats) It will likely take a few years for king stocks to rebound if the ocean is truly entering a more productive regime, but just as this downward trend seemed sudden, an upward trend can also seem to turn on a dime. This is particularly true in rivers with high-quality habitat and for hatchery production.
Turning back on a dime will require adequate numbers of spawners. The sacrifices made to conservation of stocks in 2018 are required for a bright king future. We see no reason to believe the good old days are behind us in Sitka.
The statistical reasons for the king salmon regulations are well explained in the State of Alaska document:
The Basis for 2018 Chinook Salmon Conservation Measures in Southeast Alaska pdf