DNR Question a da week?

[Lee Borgersen]

             DNR  Question of the week?


Q: What makes certain streams good for trout?

A: Streams that hold trout are usually an indicator of healthy water quality and responsible land use. Trout require fairly consistent stream temperatures year-round – cold water in the summer and water that doesn’t freeze in the winter. In Minnesota, this comes from groundwater inflow since we don’t have mountain snowpack like some Western streams.

Good trout streams also tend to be relatively clear and free of excess sediment. When stream banks become eroded, trout eggs can become covered in silt, water quality suffers and aquatic insects that trout feed on may decline. Deep-rooted grasses alongside streams help to stabilize the banks, prevent erosion and filter out sediment from the surrounding land.

In addition, trout streams benefit from stable flows. That means they need groundwater to maintain flow during dry periods and over the winter – and a natural floodplain that can disperse large amounts of water during heavy rain events.

Lastly, streams with good aquatic habitat will support more trout. This includes deep pools, riffles and cover such as vegetation, wood and undercut banks. Pools provide places for trout to rest, riffles cool and oxygenate the water, and cover adds diverse places to hide or feed. Together, these elements provide the living space for all life stages of trout throughout the year.

Mark Nemeth, DNR trout stream habitat specialist