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About SPU
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Management
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SPU & the Environment
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Salmon Friendly Seattle
Salmon Habitat Needs
Spawning Adult Salmon
When adults spawn, they need the right stream gravel, or substrate, for their nests. Each species has unique spawning area requirements, including substrate size, area, depth, and water velocity. Spawning adults also need clear, clean, and cold water. A female salmon’s energy reserves are often depleted by the time she digs her redds. She cannot handle high temperatures, water filled with sediments, low water levels, and low oxygen levels on the journey to her spawning grounds. If these stresses become extreme, she will die before spawning.
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Fertilized Eggs
When fertilized eggs mature into embryos, they need a constant supply of clean, cold, and clear water. This water flows through the gravel in the redds (or nests) providing oxygen to the growing embryos and removing waste products.
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Hatched Salmon
When freshly hatched salmon, or alevins, mature into fry, they need plenty of food in the form of microscopic plants and animals, called phytoplankton and zooplankton. Fry also need slower-moving water when they emerge from the redd, because they are not strong enough to swim in swift currents. Shallow water habitat, usually in backwaters, supplies these slower currents and protects the fry from floods.
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Depending upon the species and region, juvenile salmon live in freshwater streams, rivers, or lakes from several weeks to several years before they migrate to the ocean. Sockeye salmon spend one to two years in lakes before migrating. In contrast chinook, pink, and chum salmon in the Puget Sound region spend only a few weeks to a few months in streams and rivers before migrating downstream. During this time, they need habitat with boulders, wood, deep pools, and side channels that can shelter them from predators and high currents.
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Frys Mature
When fry mature into smolts, they undergo physiological changes so that they can live in salt water. Shallow estuary areas with brackish water (a mix of salt and fresh water) help smolts adjust gradually to the ocean’s salt water. These areas also supply smolts with abundant food, helping them grow and improving their chance of survival after they migrate into the ocean. Lastly, shallow areas can provide refuge from predators. Some smolts migrate quickly to the ocean, while others migrate more slowly. As weak swimmers, chinook smolts need fast flowing currents during downstream migration.
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Smolts
When smolts grow into adults, they need ample ocean food. Unfortunately, little is known about this part of the life cycle, and it is different among different salmon species and regions. Some adult salmon migrate long distances once they reach the ocean, moving along the coast of northern Washington, British Columbia and Alaska before returning to the Puget Sound.
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Adult Salmon
When adults return to spawn, they need unobstructed passage, and cold, clear, and clean water. Adult salmon returning to spawn do not eat but instead tap into fat and muscle energy reserves built up during several years in the ocean. Since they have limited resources, they need quick access to the stream where they were hatched, and barriers to passage create stress. These adults also must be able to recognize the smells that they learned as smolts, because those smells guide them back to their home waters.
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