Brown Trout
(Salmo trutta)
 

For more information about the trout in Seven Mile Creek, contact the Minnesota Department of Natural Resources, Waterville Area Fisheries at 507-362-4223.

Physical Description & Behavior

The Brown Trout is native to many parts of Europe and is a relative of the Atlantic Salmon.
Length: 16-24 inches
Weight: 2-8 pounds (however in larger lake environments they can reach up to 30 pounds)
Color: Light Brown/Tawny Black turning to silvery on the belly
They are very cautious fish and feed mostly at dusk and night on insects, smaller fish and frogs.
Nicknames: Brownie, German Trout, European Brown Trout and Breac.


Habitat
• Like all trout, the Brown Trout is fairly demanding in terms of water quality. They can’t live in polluted, warm, or acidic streams. However, the Brown trout is remarkably adaptable and is able to live in waters that are no longer suitable for Brook Trout.
• Brown Trout can live in either fresh or salt water.
• They have been introduced to many lakes and streams in the United States including the Great Lakes and Seven Mile.
• Spawning occurs in the fall in streams like Seven Mile Creek.
• They are usually found in the deeper pools in the streams where the flow is slower.

Conservation Efforts
• The official designation of the Seven Mile Creek is ‘marginal trout stream’.
• The Brown Trout is an indicator species, meaning that if they can live in a stream, it is a fairly clean stream.
• In 1986 the DNR started stocking 7,500 trout in the stream. They live for several years and can grow up to 20 inches. They are not known to spawn in the creek yet.
• Creating more pools and directing water flow is being considered for the Seven Mile Creek in order to improve the habitat for the Trout.
• Efforts are being made to make the Seven Mile Creek even cleaner.
• Major sources of pollution are bank erosion (producing sediments), tile lines (nitrates) and failing septic systems (bacteria) in the Seven Mile Watershed. It is essential that we take care of the creek if we want to continue to have fish such as the Brown Trout living here.

In addition to temperature requirements, brown trout need clean water to live and spawn in. For that reason, brown trout are considered to be an indicator species. The success of trout populations serves as a clue into the health of a stream. A Department of Natural Resources fish survey report published in 1996 cited "unstable flows [and] lack of pools and suitable cover" as the predominant challenge to Seven Mile Creek's fish capacity and sutainability issues.

What Do Trout Need?

A stream that maintains year-round flow and water temperatures less than 75 degree F Gravel substrate on which to spawn.
Sufficient oxygen levels and circulation to supply eggs with oxygen and prevent them from being silted over.
Protection and cover provided by riparian vegetation.

What Threatens Their Habitat...
Cutting off recharge to the spring which maintains cool water temps in the summer and prevents icing over in the winter.
Excessive erosion rates that silt over spawning grounds and suffocate developing eggs.
No flow in winter months (with the exception of the spring) and oxygen depleting algae blooms stimulated by influx in agricultural runoff.
Vegetation is absent from the banks throughout much of the channelized portion of the creek within the park.

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