This is the first in a two-part series on the decline of salmon runs. Click here for part two.

Salmon runs have steadily declined in Lake Washington for nearly 40 years, a phenomenon which has not escaped researchers, ecologists and environmentalists.

The Cedar River-Lake Washington watershed runs from Snoqualmie Pass all the way to Puget Sound in an expanding cone-shaped perimeter, with tributaries from Lynnwood to Renton pouring into Lake Washington.

The Cedar River is the main tributary for the watershed, providing access to fertile spawning ground for Chinook salmon and other fish in south Lake Washington.

The Sammamish River winds from Lake Sammamish in Redmond through Woodinville, Bothell and finally into Lake Washington in Kenmore, providing salmon access to Bear Creek and North Creek, primary spawning habitats.

Salmon runs used to be a prominent feature of Lake Washington and Puget Sound, but their numbers have dramatically declined following decades of shoreline development, contamination and increasing wetland urbanization, prompting ecology experts to galvanize governments and private landowners to try and carve out a place for salmon in the rapidly developing greater Seattle area.

A tough cycle

“It’s tough being a baby salmon,” Adopt-A-Stream director Tom Murdock said as he described the life cycle of a Chinook salmon in northern Lake Washington.

Salmon are born in the Sammamish River tributary streams, primarily Bear Creek and North Creek, he said.

A female salmon digs out a nest, known as a redd, and lays hundreds of eggs before multiple male salmon fertilize them. They are then buried under gravel and left to hatch, after which the newly born salmon either stay in their stream, or move farther down into the Sammamish River and Lake Washington for around six months to a year.

Chinook salmon then move out to Puget Sound through the Ballard Locks in Seattle, and ultimately may end up in the Pacific Ocean, where they live for years before returning to spawn in the same streams in which they were born.

It seems simple enough, but Murdock said every step of the process is fraught with dangers stemming from complex and varying circumstances.

Jim Myers is a fisheries biologist with the National Oceanic and Atmospheric Administration, or NOAA. The Kenmore resident’s work deals with area salmon populations.

“Most of the concern now has been all the great changes that we’ve had with the freshwater ecosystems, making sure that they’re still capable of supporting salmon,” he said.

Dwindling salmon counts

According to data from the Department of Fish and Wildlife, which has tracked Chinook salmon runs based on live fish in the Sammamish River and Lake Washington since 1983, there is a severe decline in the salmon population.

In 1983 there were an estimated 550 naturally-spawning Chinook salmon in the region, reaching low points of 33 salmon in 1996 and 2011.

In 2004, tracking began for hatchery-spawned salmon with an estimated 784 hatchery fish and 228 natural salmon in the region.

Both populations nose-dived between 2014 and 2015, with a combined total population of 1,578 Chinook salmon in 2014, dropping to only 482 in 2015, only 35 of which were naturally-spawning. Chinook salmon are an important part of Puget Sound and northwest’s resident Orca population as their preferred source of food.

“For the resident pods, which are listed now under the endangered species act, there’s a lot of concern that the health of the local salmon runs are closely tied to the health of our Orca pods,” Myers said.

Chinook salmon are also an important part of many Native American cultures.

Development puts the squeeze on salmon

Many of the biggest challenges to salmon habitat comes from human development.

Hard surfaces within a watershed area, even miles from bodies of water, don’t allow rain water to seep into the ground, which would normally be absorbed and filtered into the ground water supply. These surfaces include parking lots, roofs and sidewalks among other structures, as well as drained wetlands, which would normally act as natural sponges.

This both reduces fresh ground water in tributary streams and lets unfiltered runoff, full of chemicals, wash into streams and rivers. This is one of the most abrupt causes of salmon death, Myers said.

“For us, that’s such a horrible thing because fish have made it all the way back… to their spawning stream, and then they get hit by this toxic cocktail of chemicals that’s just completely lethal,” he said.

When water cannot soak into the ground, it is channeled into existing streams and rivers as runoff. This increases the water flow and volume in these streams.

In salmon spawning streams, Murdock said, these increased flows often scour the salmon redds, destroying them, or packing silt and sediment over them, blocking oxygen flow and suffocating them.

Stormwater runoff is warmer than groundwater when it enters streams.

Chinook salmon are highly susceptible to changes in water temperature. If the water is too hot, the salmon will stop where they are and wait until it cools down, sometimes staying put until they die, said Jason Mulvihill-Kuntz, Watershed Coordinator for the Department of Ecology’s Water Resource Inventory Area Eight serving the Cedar River-Lake Washington Watershed.

“Sometimes some of them will die before they get a chance to get up there,” he said. “A lot of that’s about restoring the stream-side vegetation to keep shade on the river.”

Replacement of natural shoreline with concrete barriers or other hard materials is another killer, with landowners and developers often hardening shoreline to prevent erosion. Areas of vegetation along streams or rivers are known as riparian zones.

Riparian zones often contain overhanging plants which drop leaves, pollen and other material into the water, providing food for bugs and other creatures which fish end up eating. It can also provide a place for juvenile salmon to hide from predators such as larger trout species.

“If you look at any of these stream systems around Lake Washington, you will find very few areas where the riparian zone is of significant size,” Murdock said.

The Sammamish River itself is considered a slough, with slow water flowing through a winding path already causing it to heat up, especially in the summer and fall when the water level is lower.

Mulvihill-Kuntz also noted warm water is a problem in the Ballard Locks, where slower water is allowed to heat up. He said many salmon will make it up the fish ladder, which is full of cool water, before suddenly being dropped into hot water.

Man-made blockages along spawning streams also make it harder for adult salmon to get upstream, and smaller salmon to make it into Lake Washington.

One small stream which enters Lake Washington near Kenmore’s Log Boom Park, known as Stream 0056, or Little Creek, has around 60 barriers. Thirty-eight percent of them, Murdock said, belong to the cities of Brier, Lake Forest Park and the Department of Transportation.

Under Washington State law, entities who own fish migration barriers are required to remove them, but he said due to the cost of removal, enforcement has been lax.  The Department of Fish and Wildlife’s interactive Salmonscape map also documents other barriers along North and Bear Creeks.

In the next report, concerned residents and local and regional leaders try to tackle problems associated with diminishing salmon runs.