They came up with seven hypotheses for the decline. Natural cycles are cited, but the report returns again and again to climate change. Rivers are breaking up earlier along their routes, sending more vulnerable juveniles out into the ocean. Changing ocean currents may be spreading disease. There are shifts in other species in the food chain upon which the salmon depend. Warmer waters are depleting the energy of the fish, causing higher mortality rates along the migration route. The impact of each of these factors is currently unknown.
In June 2012, after Fish and Game announced a ban throughout the Delta, State Trooper Brett Scott Gibbens was sent out to patrol the rivers around Bethel, the central hub of the Yukon-Kuskokwim Delta. He’d learned, through a press release, that a group of Yup’ik fishermen planned to defy the ban, and as he came down the Kuskokwim River, he found a small fleet of boats—somewhere between 12 and 16, he later testified. The gill nets they were using were perhaps 50 fathoms long, which made them illegal under the ban. Many of the fishermen pulled their gear and left as he was identifying and rounding up the others. Some of the fishermen later went on to pay fines. But 23 of them refused, and last summer, they stood trial in a Bethel courtroom.