From the Department of Fish and Game:

The Kasilof River will be restricted to catch-and-release fishing for king salmon, effective 12:01 am, Tuesday, July 10, through 11:59 p.m., Tuesday, July 31.
King salmon runs to Cook Inlet and throughout Alaska are experiencing a period of low productivity and low run strength. The department has no information indicating that the Kasilof River late-run will experience average or above average run strength. The prohibition on the use of bait and catch-and-release restrictions at the Kenai River, and additional restrictions in Lower Kenai Peninsula streams as well as saltwater fishing areas of Lower Cook Inlet during July would likely result in an increase in the sport fishing effort and harvest of late-run king salmon at the Kasilof River during July.
Therefore, this measure is warranted to prohibit retention of Kasilof River late-run king salmon.