In the Pacific Northwest, salmon are a famous species because of the dramatic way they move from the ocean up fast-moving rivers to spawn. But salmon are more than just a cultural icon; they are very important to the health of ecosystems from mountain streams to the open ocean. Understanding why salmon are so important can help drive efforts to protect these endangered fish.
Salmon Shape Mountain Streams
Salmon shape the physical structure of the rivers and streams where they spawn. Pink salmon dig nests, or redds, in the gravel at the bottom of rivers with their tails. This moves rocks and gravel around, making riffles and pools in the stream that are good places for other aquatic animals to live. Salmon also supply streams with nutrients that fertilize the whole watershed.
When salmon migrate from the ocean into streams, they bring a banquet of marine-derived nutrients. Salmon accumulate over 90% of their biomass while feeding in the ocean. When salmon return to freshwater to spawn and then die, their decomposing bodies release nitrogen, phosphorus and carbon into the streams. Researchers have traced salmon nutrients fertilizing over 500 meters downstream and boosting growth in trees over 500 meters from the streams.
Salmon Sustain Food Webs
Along their migration routes and in the streams where they spawn, salmon are a feast for more than 130 species of wildlife. Grizzly bears are known to gather at streams where salmon spawn to put on weight before going to sleep for the winter. Over 90% of the nitrogen in grizzly bears that live along Alaska’s McNeil River comes directly from salmon.
Bald eagles, osprey, gulls and a host of other birds rely on salmon runs for sustenance Aquatic species like river otters, seals, orcas and fish directly consume salmon, while dozens of mammals and birds eat salmon eggs and carcasses Even tree growth is linked to salmon runs, since trees absorb more nutrients when salmon are present.
In fact, when salmon populations decline, the populations of dependent predators like bears, eagles and orcas also decline This demonstrates how vital salmon are in sustaining food webs stretching far beyond the streams where they spawn
Salmon Benefit Coastal Ecosystems
The influence of salmon extends all the way from mountain streams to coastal rainforests Salmon transport nutrients from highly productive ocean waters to less productive inland areas when they return home to spawn and die This movement of nutrients from ocean to land by salmon is called “guano subsidy”.
Up to 40% of the nitrogen in coastal rainforest plants comes from spawning salmon. The trees and plants make use of the marine-derived nitrogen for growth. Bears then eat the salmon-fed plants, continuing the nutrient cycle.
This guano subsidy also fertilizes estuaries and nearshore ocean habitats. The carcasses of spawned-out salmon enrich estuary sediments. Juvenile salmon feed on marine life proliferating in the fertilized estuaries before heading out to the ocean, benefiting from the nutrients their parents’ carcasses provide.
Factors in Salmon Decline
If salmon are so important ecologically, why are salmon populations declining? Human activities have degraded the freshwater and ocean habitats salmon need to survive.
- Dams prevent access to historical spawning sites and alter flow patterns
- Logging increases siltation, raises water temperatures, and removes trees stabilizing streambanks
- Urbanization leads to polluted stormwater runoff and removal of habitat
- Overfishing depletes populations, especially when coupled with habitat loss
- Hatcheries weaken adaptations of wild fish through interbreeding
Climate change presents an emerging threat by raising water temperatures in spawning streams and altering ocean food chains. Protecting remaining high quality habitat, removing dams on key rivers, and addressing climate change are critical to salmon conservation.
Protecting Salmon Protects Ecosystems
Salmon were once so abundant in Pacific Northwest rivers that eyewitnesses described being able to walk across streams on the backs of fish. Current populations are mere vestiges of historic numbers.
Yet even in their reduced state, salmon provide vital connections between land and sea. Like stitches in a tapestry, salmon bind coastal, estuary, stream and forest ecosystems together through the flow of nutrients.
Salmon demonstrate that no species exists in isolation. Protecting salmon means protecting the web of life that relies on these remarkable fish. By working to conserve salmon, we can maintain resilient ecosystems that benefit all living things, from orcas to eagles to forests, and humans as well.
Call to Action
You can help protect salmon and their ecosystems:
- Advocate for dam removal and habitat restoration
- Reduce your impacts – limit pollution, avoid stormwater runoff
- Eat only sustainably caught salmon
- Learn about salmon life cycles and share with others
- Volunteer with stream restoration efforts
- Support conservation organizations working to protect salmon
The fate of salmon and the fate of their ecosystems are intertwined. With small daily actions and voices raised in support of salmon, we each have the power to make a difference for these vital fish.
Why Are Salmon Important To The Ecosystem
Salmon are vital for the economies of coastal communities, especially those in the Pacific Northwest. Wild salmon also play a critical role in ecosystem heath, from the ocean, to mountain streams and forests. It is eaten by more than 130 animal species, like the Orca whale and the Grizzly Bear. The protein and nutrients in salmon are good for them. People also eat a lot of salmon, especially people who live along the coast and have fished for salmon for thousands of years. Wild salmon went out of many rivers in the 20th century because of overfishing, habitat loss from things like building dams, and pollution in the water. Salmon populations are going down, which is making people unhappy. This has led to calls to return river systems to their natural states so that salmon can return to mountain streams.
Why do salmon migrate up rivers?
Seven types of salmon live in the Pacific Ocean. Five of these species live and breed in water in North America. These species are Chinook, Coho, Chum, Sockeye, and Pink salmon. The largest species of salmon lives in the Atlantic Ocean – the Atlantic Salmon. The Chinook salmon is the biggest type of Pacific salmon. It can get up to 5 feet long and 126 pounds heavy. The smallest salmon species is the Pink salmon, which only reach about 2. 5 feet long and weigh up to 12 pounds. These important fish depend on the connectivity between oceans and rivers for a key component of their lifecycle. Salmon spend most of their lives in the ocean, where there is a lot of food and nutrients. They are called anadromous fish because they can swim back to land. In other words, they swim up river mouths and lay their eggs upstream, where they are safe from marine predators. Strong currents and rapids make it hard for salmon, but every year they swim tens to hundreds of miles upstream to spawn. They do this in big rivers like the Columbia and the Fraser as well as in many small rivers that reach the coast. Salmon usually choose to lay their eggs in riffles, where the water is shallow and moving quickly and rough. Their nests are called “redds,” and they are small depressions in the gravel river bed that the female salmon makes with her tail. She makes a shallow hole where she can lay her eggs by fanning her tail over the gravel. This causes the gravel to rise up from the river bed. To protect the eggs from being eaten, she swims upstream of the nest and spreads out more gravel to cover them. Because of this unique spawning behavior, salmon need coarse river gravel with a diameter up to 4 inches. This size of gravel not only protects the eggs, but it also lets water flow through and gives the eggs the oxygen they need to grow. Female salmon typically die within a week after laying their eggs because spawning is so taxing. For example, the Pacific salmon lives in the ocean for many years before migrating up rivers to spawn. However, they die after laying their eggs, so they only spawn once in their lifetime. Because these salmon die in upstream parts of rivers, the plants and animals in the area benefit from the nutrients the salmon brought in from the ocean. In this way, the salmon life cycle helps the different ecosystems that live along the Pacific Northwest coast.
Salmon’s life cycle and their incredible impact on our ecosystem
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