Doug, the retired ADF&G Kuskokwim Area Research Biologist, posted this explanation on Facebook recently of what is likely going on with the king salmon of the region.
The Kuskokwim (and Yukon) are not due to overfishing, but fishing could protract or worsen the decline if public harvest expectations and practices do not change. There is debate as to the specific root cause or causes of the recent declines, but most accepted is climatic changes in the Bering Sea that are just not favorable for survival of kings salmon. Below is graph of the deviation in mean sea surface temperature (SST) of the Bering Sea that shows recent years (2005 to 2011) as being below average in temperature; i.e., “cool”. These correspond well to dips in king salmon run abundance in the Kuskokwim.
A cool Bering Sea is just not so good for growing king salmon. Other salmon species are doing fine, especially chum salmon, but these species have a much wider ranging ocean migratory path that includes the north Pacific Ocean. In contrast, Kuskokwim and Yukon kings pretty much stay in the Bering Sea throughout their marine residency.
But salmon have a history of being resilient if they have access to good habitat for spawning and rearing. The Kuskokwim and Yukon rivers still have plenty of excellent habitat, so the conditions exist to allow them to rebound. The challenge is to make sure the we allow the kings to rebound by ensuring adequate numbers get to the spawning grounds each year (“escapement”) to put their eggs into the gravel. This is where public harvest expectations and practices need to change. The biggest harvester of king salmon is the subsistence fishery which, unfettered, takes 70,000 to 100,000 kings each year (30% to 60% of the total annual run).
That harvest needs to shift from kings to the other more abundant species like chum salmon. Harvesting more chum is actually more in line with fishing patterns in the days prior to modern drift gillnets and powerful outboard engines, or so I am told by elders. The public often likes to look to the king bycatch in the Bering Sea pollock fishery as the problem, but regulatory changes in recent years have contributed to reducing that bycatch to what is probably only about 2,000 Kuskokwim kings each year (2% of the total annual king run), which pales to the 70,000 to 100,000 annual subsistence harvest. The bycatch does not account for the 100,000 kings that seems to be missing from the annual run in recent years.
Subsistence fishing practices within the Kuskokwim River also need to shift from the large mesh gillnets that target larger female king salmon, to smaller gillnet mesh sizes that take more of the smaller and predominantly male kings. Otherwise, we risk “achieving escapement goals” but mostly with male fish such that we fail to get vital eggs in the gravel. This is my biggest concern with the recent lowering of king salmon escapement goals – not getting enough females to the spawning grounds. It takes fish to make fish, and females are a critical part of the equation.