For evaluation of streams with the biotic index (BI), samples of arthropods should be collected in the spring before degree day accumulations of mean air temperatures above 4.5°C reach 440° in warm-water streams, and before they reach 1050° in cold-water streams that remain below 20°e. Sampling in the fall may be resumed 60 days after the 440 degree day accumulation in warm-water streams and 45 days after the 1050 degree day accumulation in cold-water streams. Stream temperature had no effect on the BI, except as it affected seasonal differences. Current had less effect on the BI than anticipated, but currents below 0.3 m/sec should be avoided.
Hilsenhoff, William L.
"Seasonal Correction Factors for the Biotic Index,"
The Great Lakes Entomologist, vol 21
Available at: https://scholar.valpo.edu/tgle/vol21/iss1/3