Physical Parameters of Microhabitats Occupied by Brown Trout in an Experimental Flume

Physical parameters govern microhabitat characteristics. A resting microhabitat for fishes in streams becomes the focus for movement to other segments of the habitat. Brown trout were observed in a flume at flows of 0.37, 1.10, and 2.07 cm3/sec (1.2, 3.6, and 6.8 cfs). Study fish occupied resting microhabitats within a velocity range of 12.2 to 21.3 cm/sec (0.4 to 0.7 ft/sec). Turbulence, light, water depth, spatial limits, direction of flow, and cover also influence selection. Most microhabitats were above structures or along the edge on the shaded east side of the flume. Study fish occupied areas near the bottom and were positive rheotactic. A strong thigmotactic response substituted for lack of overhead cover. Areas less than 5.1 cm (2 inches) deep and less than 20.3 cm (8 inches) square within the suitable velocity range were avoided.