North Cascades

Salmon's Requirements for Life

The three most important factors that influence stream habitat for salmon are water quality, water quantity, and the physical structure of the stream.

Water quality includes water temperature, chemistry, and turbidity:

Salmon are cold-blooded. The rate of their body activities is directly related to the temperature of the water.

Salmon can survive within a temperature range of 42-88 degrees Fahrenheit, although 55 degrees Fahrenheit is ideal. Temperatures are affected by the rate of flow of the water, the water's turbidity, and variations in the region's weather. The temperature also affects the amount of dissolved oxygen that the water carries.

Salmon prefer water that is a neutral pH of 7; it is neither acidic or basic. Unnaturally high concentrations of toxins or pollutants create direct and indirect hazards for salmon. Such substrates can affect the population of organisms upon which salmon feed, thereby creating an inadequate food supply. Salmon may feed on tainted insects, resulting in illness and/or death of the fish. Certain chemicals can be tolerated by some organisms, but these chemicals build up in their body tissues and are passed on to other predators and, thus, through the food chain.

Oxygen that is dissolved in water is necessary for the respiration of aquatic animals. Fish take in this dissolved oxygen through their gills. The amount of dissolved oxygen in the water system affects the efficiency of oxygen uptake by aquatic animals and affects their ability to function efficiently in their environment.

In April 1991 an agreement was signed which is crucial to the survival of salmon in the Skagit Watershed.

This agreement stipulates that Seattle City Light will provide adequate water flow in the Skagit River, downstream of Gorge Powerhouse in Newhalem, to assist in perpetuating salmon occupation of the watershed. Specifically, Seattle City Light will limit maximum flow levels and maintain minimum flow levels during the migration of adult spawning salmon, while salmon eggs occupy the redds and until fry emerge, and for the length of time the fry commonly inhabit the gravel beds.

The Fisheries Settlement Agreement brought together the City of Seattle, City Light Department and the U.S. Department of the Interior, National Park Service; U.S. Department of the Interior, Fish and Wildlife Service; U.S. Department of the Interior, Bureau of Indian Affairs; U.S. Department of Agriculture, Forest Service; U.S. Department of Commerce, National Marine Fisheries Service; Upper Skagit Tribe, Sauk-Suiattle Tribe, and Swinomish Indian Tribal Community; Washington Department of Fisheries; Washington Department of Wildlife; and the North Cascades Conservation Council. (Skagit River Hydroelectric Project. Fisheries Settlement Agreement. 4/91)

Water quantity:

High water flow can be hazardous to salmon at all life stages. This condition can result in eggs being covered by silt and other materials, can cause eggs to wash out of the gravel, move juveniles downstream too quickly, and make it too difficult for spawners to return upstream.

Low water affects salmon populations by isolating eggs and juveniles in pools whose temperatures increase while the dissolved oxygen content decreases, and also causes them to be more susceptible to predation. Low water makes it difficult for out-migrating juveniles and in-migrating spawners to reach their destinations.

"The rate of water movement influences the types of organisms found in the stream, affects the transport of nutrients through a system, affects the transport of suspended solids and sediments, adds oxygen necessary for organisms which inhabit the stream by rippling of surface waters and aeration activity, provides greater evaporation which has a cooling effect temperature wise, affects the composition of the stream bed." (Small Streams and Salmonoids: A handbook for water quality studies. Dyckman, C. and Garrod, S. Eds. United Nations Educational, Scientific, and Cultural Organization. 1980. p.46)

Physical structure of the stream:

A productive salmon water system needs to have pools, riffles and rapids, side channels, and woody debris.

Pools are a crucial factor because they offer hiding places amongst boulders and woody debris for young fish and areas of respite for migrating adults. Riffle and rapid areas mix air with the water, thereby increasing the oxygen content of the water; these areas support a richer concentration of aquatic insect larvae (salmon food!) than slower moving parts of the water system. Woody debris creates riffles and rapids, and contributes to the formation of pools. The debris also gives aquatic insects shelter. Side channels are rich in aquatic insect life and are important habitats for juvenile salmon. These areas also provide places of escape for juveniles during high water.

The cumulative impact of urban development, industry, mining, agriculture, fishing, and forestry, has had serious effects on the health of the population of salmon that call the Skagit River Watershed their home.

The Importance of the Survival of Salmon

Salmon depend on both the salt water and the fresh water systems. They have far-ranging territories. The health of their populations indicate clear interdependencies between the two water systems and the stability of both systems is imperative to the survival of salmon.

Salmon are indicators of the health of the Skagit River Watershed, of the Greater North Cascades Ecosystem, and beyond. Strict environmental requirements exist for a healthy salmon population. Salmon find nourishment in all sections of the watershed. Their flesh, in turn nourishes many creatures. They are connected in a web of life that includes us. Salmon populations are decreasing worldwide for a reason. The Skagit Watershed is changing. We can look toward salmon as an indicator of the health of our environment and as a barometer for the wisdom of our decisions.