California Department of Fish and Wildlife press release:

The spit fishery at the mouth of the Klamath River will be closed to angling at 11:59 p.m. on Monday, Sept. 3. Based on California Department of Fish and Wildlife (CDFW) projections of the recreational fall Chinook salmon harvest, anglers will have met the “spit area” adult fall Chinook quota of 15 percent of the total Klamath River Basin allotment by that time.

Meeting the quota triggers the closure of the spit fishery at the mouth of the Klamath River, within 100 yards of the channel through the sand spit formed at the Klamath River mouth. The spit area is downstream of the Highway 101 bridge located near the town of Klamath.

Recreational fishing will remain closed to all fishing for the remainder of the 2018 season.

Anglers may keep track of the quota status of open and closed sections of the Klamath and Trinity rivers by calling the information hotline at (800) 564-6479.
More information is available online here.