April 29, 2022
April 29, 2022
By: Caroline Woodwell, Volunteer Writer
This is the full story “Return” from the Conservancy’s spring 2022 newsletter. Be on the lookout for your copy in the mail, or email the office if you need to be sent one!
Humans get to choose. We are born, we’re raised, and when we go out into the world, we make a home where there’s a job, a spouse, recreational opportunities, natural beauty. Whether we recognize it or not, most of us have had something to say about where we are going to live and where we are likely to die.
Not so for the mighty salmon.
The course of life for salmon, both female and male, is governed by a powerful instinct; the drive to return to its place of birth to lay the next generation of salmon. That cycle, established over the six million years since salmon appeared on Earth, is at the heart of the ecological processes that have defined the rivers and streams, the patterns of wildlife, and patterns of human settlement in the Inland Northwest over generations.
Salmon are important culturally and ecologically in large part because they are anadromous: born in freshwater, they grow to maturity in saltwater, then return to freshwater to spawn and die. This puts them in the tributaries, streams, rivers, and the ocean of the Pacific Northwest. It means that, at every stage of their lives, they are easily available to humans. It also means they are an integral part of the ecological processes of the region.
Salmon increase the ecological richness of streams and tributaries by carrying nitrogen from one place to another. Plants require nitrogen to grow. In fact, nitrogen is one of the limiting factors for plant growth. Limited nitrogen means limited plant growth, and plants are the sole source of photosynthesis, which turns energy from the sun into fuel for life on Earth. No nitrogen, no plants, no photosynthesis, no life.
When salmon leave saltwater and go upriver to spawn and die, Spokane Riverkeeper Jerry White says, their tissue is full of ocean nitrogen. When they die, that nitrogen is released into the soil where it acts as a fertilizer for green plants.
“Nitrogen drives the ecosystem,” he says. When salmon bring nitrogen, “you see a more vibrant riparian vegetation, you see insects that thrive, macroinvertebrates, and that in turn feeds other small fish including the progeny of the fish that spawned.”
So, salmon increase the ecological richness of streams and tributaries by carrying nitrogen from one place to another.
Salmon also drive the diversity and the range of animals in the food chain. Kingfishers, otters, osprey, eagles, and bears all feed on fish. Where salmon exist, the animals that feed on salmon thrive. When salmon disappear, their predators must move or find another food source. When they are free to travel the full range of their habitat, salmon provide food and nutrients, enriching ecological diversity throughout the 250,000 square miles of the Columbia River Basin.
Animals that fill multiple functions in an ecosystem are often identified as “keystone species.” This term was coined by Robert Paine, a researcher at the University of Washington. In 1963 he removed all the predatory purple sea starfish from a stretch of Washington shoreline and left them alone in a nearby stretch. These starfish feed on mussels. They limit growth of the mussel population. Without the starfish, mussels took over the area and ecological diversity — which is a critical measure of ecological stability — plummeted. Starfish are a keystone species in that ecosystem; their absence changes the relationships between species, reduces ecological diversity, and impoverishes the system.
Salmon are considered by many to be a keystone species in the Pacific Northwest. Their absence in the upper reaches of the Columbia River Basin has changed the distribution of other species, including birds such as eagles and kingfishers, and mammals such as otters. Many have speculated, Mr. White says, that damming the North Fork of the Clearwater ended one of the last sources of salmon for the remnant grizzly bear population in that part of Montana and Idaho.
In the United States, we have one species of salmon on the East Coast, Atlantic Salmon, and five species on the West Coast: chinook (also known as king salmon), coho, pink, sockeye, and chum. Both East Coast and West Coast salmon are anadromous.
Let’s take a look at the life cycle of these animals that fill such an important ecological role in our region.
Every spring, salmon, both male and female, leave the ocean and swim upstream. Guided by Earth’s magnetic field they find the stream where they were born. Using their sense of smell as they get closer to the exact spot of their birth, the male will find a gravel bed with pebbles of a perfect size and water flow sufficient to oxygenate the eggs but not wash them out of the gravel bed.
The female will use her tail to make a shallow depression, or redd, in the gravel. Hovering side-by-side, the female and male will release gametes. She may lay between two and ten thousand eggs, each the size of a small pea. The male milt contains millions of sperm.
Having filled one redd, the pair will swim upstream and repeat the process in another redd. Their movement at the second redd washes gravel downstream to cover the first redd, protecting it from flowing water. The salmon will continue this process until they have depleted their gamete reserves. Within a few days, they die.
In death, they fall to the bottom of the stream or end up on the river bank, where they decompose, becoming food for larger animals, and nutrients for the ecosystem.
About four months later, the young salmon hatch. For the first month, before they begin to eat insects, they are fed from the yolk of the sac where they developed. Eventually, they begin their journey downstream to the ocean where they feed on plankton, other fish, squid, and shrimp. They are building muscle and gaining the oil that characterizes salmon. They may stay close to the mouth of the river where they spawned, or they may travel far out into the ocean. But several years later, inspired by environmental factors such as length of the day and water temperature, they head back up the river.
Salmon go through a remarkable physiological change during their upriver journey. They stop feeding and their stomachs begin to shrink as they enter freshwater. Nourished by stored fat, their flesh grows soft and mushy (most salmon caught for human consumption are harvested from the ocean while the fish flesh is lean). They grow pale in color. And their hydrologic cycle changes.
Ocean water dehydrates salmon, so while they are in the ocean, they drink seawater, extracting the salt through a salt gland – you could think of it as an on-board, personal de-salinator. When they return to freshwater, they absorb water and begin to bloat. To counter that absorption, they increase the rate at which they process urine.
The upstream trip takes enormous energy. The fish must swim against strong water, often leaping over big rocks and waterfalls, as their bodies are changing physiologically and they are preparing for reproduction. If all goes according to plan, they will make their way to the very stream and the very spot where they hatched several years ago. There, they will find a mate and, in a perfect world for salmon, the cycle will begin again.
But it’s not a perfect world for salmon.
Starting in the 1930s the US Army Corps of Engineers began to dam the Columbia River. Today the Corps counts 250 reservoirs, and about 150 hydroelectric projects including 18 mainstem dams on the Columbia and the Snake Rivers. The result, according to the US Government Accountability Office, is that the estimated number of salmon and steelhead returning to the Columbia River Basin annually dropped from 16 million before the construction of the dams to about 660,000 a year today. (https://www.gao.gov/products/gao-02-612)
Last summer, your Conservancy joined the Spokane Tribe of Indians in a release of 50 chinook salmon into the Little Spokane River near the Waikiki Spring Trailhead. The project is part of a larger salmon reintroduction project undertaken by the Upper Columbia United Tribes, who are working to reintroduce salmon to the streams and tributaries of the Upper Columbia Basin.
They are not advocating for dam removal, says Brent Nichols, Division Director at Spokane Tribal Fisheries. Instead, they are “recreating what was once here, within the given parameters we have, under operational constraints from the hydropower system.” That means capturing salmon as they begin their journey to freshwater, trucking them around the dams, and setting them free in the tributaries where they will spawn and die. Tagging the young salmon before those fish head downriver allows scientists to track how many make it downriver and back up.
They have some early results. In 2019, of 800 juvenile Chinook released into a creek on the Spokane Indian Reservation, Mr. Nichols said, 90 were tracked through Little Falls Dam, Chief Joseph, past Bonneville. Five of them returned. One made it back to the Chief Joseph hatchery fish trap. Three made it past Wells Dam and got caught by anglers or otherwise disappeared. One was harvested by a commercial fisherman who called and returned the fish to the tribe.
Is it possible to recreate the salmon fishery by working around the dams? They don’t know yet, what the end result will be, Mr. Nichols said. But, “we want healthy, sustainable, harvestable populations of salmon for this area.”
What awaits the mighty salmon?
In the end, it’s not just the ecological function filled by salmon that matters, it’s the cultural and spiritual role as well. Back in August when INLC joined the Spokane Tribe near Waikiki springs for a salmon release, Spokane Tribal Councilwoman Monica Tonasket noted the spiritual importance. “Salmon, for us, it’s kind of a spiritual experience,” she said. “Those salmon have a spirit.”
Spirits, keystone species, recreational fishery, food source for a range of animals – there are many reasons to wish for the return of salmon to the freshwater streams of the Inland Northwest.