Evaluating suitable habitat for Brook Trout (Salvelinus fontinalis) in the Driftless Area of Wisconsin between sandstone and dolostone rock geologies.

Abstract

Brook Trout (Salvelinus fontinalis) are the only stream trout native to Wisconsin and the amount of suitable habitat in the state is projected to decrease substantially. Suitable Brook Trout habitat is expected to remain within The Driftless Area in a small geographic pocket underlain with Cambrian sandstone where habitat in neighboring regions underlain with Ordovician dolostone are expected decline. Habitat surveys and snorkel surveys were conducted to assess and quantify habitat in both Brook Trout dominated and Brown Trout (Salmo trutta) dominated streams across the two geologies. Streams located in the sandstone region lacked strong microhabitat diversity and had a higher abundance of sand, greater depths, and lower current velocities. Brook Trout utilized overhead cover, aquatic vegetation, and large woody debris as the main cover types. Streams located in the dolostone region had higher abundances of rock and gravel as well as faster current velocities due to the increased presence of riffles. Brook Trout utilized rock as the main cover type. In both geologies, Brook Trout chose to position themselves in deeper and slower water than was available. Increased understanding of Brook Trout habitat requirements and use can aid in future conservation of declining populations in the state of Wisconsin.