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(5) Gravel substrate

Gravel or rocky stream substrates provide ideal spawning grounds for brook trout. Trout construct spawning beds or "redds" in the gravel to deposit their eggs. The females make the redds in the autumn. After hatching, the young trout, or "fry" stay under the stones for some time before venturing out into the open water (MN DNR).

The streambed of Spring Brook is a combination of gravel and sand which provides suitable spawning grounds. It is important that sediment does not reach the stream in large amounts that could potentially cover the gravel streambed, which would reduce spawning area and smother newly hatched trout fry.

Example of the gravel streambed of Spring Brook (photo: Jeff Jasperson)

(6) Instream debris

Much like bank cover, instream debris like fallen tree branches provide trout with necessary cover. However, if there is an excess of fallen trees, the flow of the stream can become impeded. This can ultimately lead to the formation of stagnant pools with abundant algal growths. People who own land along Spring Brook are allowed to remove downed trees from the stream, but are not allowed to remove living vegetation or alter the stream channel (MN DNR).

Fallen branches provide in-stream cover for trout (photo: Jeff Jasperson)

(7) Stream Sinuosity

The "sinuosity" of a stream refers to the degree of curvature or bends. Typically, streams with a decent amount of sinuosity have deeper water on the side the stream flows into, and shallower on the side that the stream flows away from. For example, in the photo on the left, the deeper part of the stream would be on the right side of the bend, and the shallower side would be on the left. This is caused by the deposition of sediments on the left side as the stream enters the bend. Trout prefer streams with deep, undercut stream banks, therefore a moderately sinuous stream is ideal (Hunter, 1990).

The meandering flow pattern increases the length of the channel, effectively dissipating the force of the stream's energy over longer distances than a straight channel. The result is a more stable stream.

Photo: Example of "sinuosity" on Spring Brook (Photo: Jeff Jasperson)