An organization known as the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative recently issued a research action plan to address Western Alaska's weak Chinook returns.
The plan is cumbersome reading, but Deckboss spent some time with it and offers this very brief summary.
An "expert panel" co-chaired by Daniel Schindler, a University of Washington fisheries scientist, identifies seven hypotheses thought to be the most likely causes of low Chinook returns.
Out of these seven hypotheses, the expert panel gives six the highest priority for research funding.
The one not ranked highest priority is marine bycatch — the idea that mortality from non-salmon fisheries in the ocean has contributed to the decline of AYK Chinook stocks.
The action plan states:
Based on available data, the bycatch within the domestic walleye pollock fisheries seems unlikely to have been the primary cause for the recent dramatic declines of Chinook salmon in the AYK region, because estimates of bycatch from this source are not high relative to the estimated declines in the total returns to the drainages.
The other six hypotheses include: density-dependent effects and overcompensation; freshwater mortality; ocean mortality; anthropogenic changes to marine ecological processes; escapement quality; and pathogens.
Obviously some of these are a bit technical. But the action plan contains plenty of additional detail on each hypothesis.