Tongass National Forest

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Fish Habitat

Land and climate

Glaciers have sculpted the topography of southeast Alaska, creating both steep mountainsides and flat lowland terrains with vast wetland and muskeg complexes.

Island streams in Southeast Alaska are generally short, with high gradients coming off steep mountains yielding high flows in the winter and low flows in the summer.

The combination of this geology and a maritime climate of cool summers and wet winters produces both good and bad fish habitat:

• Prime stream formations rich in nutrients necessary to support fish populations and
• Systems in which cold, turbid, high-flowing waters containing very low dissolved nutrient concentrations impede the colonization of fish.

What do fish need?

A number of attributes including physical aspects and water chemistry affect the distribution of fish.

Physical attributes include the accessibility of quality habitat to fish. For example, steep waterfalls are barriers to migration.

Water chemistry can make a stream reach hostile or hospitable to fish. Productive areas that have high pH levels, alkalinity, and dissolved solute concentration provide nutrients for fish.

Fish-friendly stream

This photo shows quality spawning gravels for coho salmon and riparian vegetation on the stream banks providing bank stability and shade. The riparian vegetation also provides undercut banks for young fish to seek cover. Leaf litter that falls from riparian vegetation into the creeks draw bacteria and fungi which form nutrients for aquatic insects (mayflies, caddisfly, and stonefly nymphs) which become prey for young salmon and trout and adult cutthroat trout and Dolly Varden char.

USDA Forest Service - Tongass National Forest Accessibility Statement
Last Modified: July 30, 2007