Dikes and levees on the Dungeness River near Sequim will play a large role in where and when chinook fishing will happen this year across western Washington.
Management planning for the 2017 salmon fishing season is underway. This year, low returns of chinook to the Dungeness River are driving fisheries planning in western Washington. The tribal and state co-managers must protect weak stocks, and the Dungeness stock is proving to be the weakest with an estimate of only 362 chinook coming back to the river.
The low Dungeness chinook return is directly linked to habitat conditions in the Dungeness River. Decades of human impacts have severely degraded salmon habitat in the lower Dungeness River. The Dungeness valley, like many river valleys, is a desirable place to live and farm. The trouble is, people built so close to the river that homes, farms and roads are threatened by floodwaters and the river channel’s natural meandering movements. In response, much of the river has been pinned down by riprap armoring and hemmed in by dikes and levees.
Disconnecting floodplains has particularly limited chinook salmon freshwater productivity. Ordinarily, floodplains will absorb the high energy of river floods. In a flood event, the river flow expands across the floodplain and slows. If the floodplain is disconnected the flood flow is confined to the channel width. The Dungeness chinook dig nests (redds) and lay eggs in the mainstem during the summer leaving the developing eggs exposed to high river velocities during the winter. The fast moving water scours deep into the riverbed greatly reducing the viability of eggs located there.
Fisheries scientists have estimated seasonal chinook freshwater productivity by comparing spawner survey data during the summer with outgoing juvenile counts the following spring. “During a non-flood winter, survival can be as high as 16 percent,” said Scott Chitwood, natural resources director for the Jamestown S’Klallam Tribe. “But when winter flooding occurs, it may be just 1 percent.” That means winter flooding can reduce productivity from as many as 800 juveniles for every spawning female down to as low as 50.
In places the natural Dungeness River floodplain width of more than 1,000 feet has been necked down to just 100 feet. Through acquisition and levee setbacks, Jamestown S’Klallam Tribe and partners are working hard to provide the river breathing room. Floodplain restoration is essential to rebuilding the Dungeness Chinook, otherwise there will be an ongoing susceptibility to winter flooding (increasing as winter snowpack is reduced), and devastating outcomes to the fishery.
Even though during the winters of 2012 through 2014 there were fewer floods and freshwater productivity between 7 and 16 percent, poor ocean conditions (the “blob”) kept chinook from taking advantage. Poor marine survival has resulted in too few adults on the spawning grounds,” Chitwood said. “So few that even when we see a couple of years of higher productivity in the river the low population size can’t take advantage.” The estimated return of 362 Dungeness chinook in 2017 is a slight improvement over the 2016 estimate of 344.