Stag.......That was really a cool video , when i was in my 20's i worked 2 summers in the Deep Creek , Oakland , area of MD and remember being drawn to check out a number of streams that had the "look" and found a few that were indeed occupied , but i remember on the ones that weren't occupied , after taking a thermometer with me it was a matter of a few degrees in temp that seemed to be the problem. To shorten this up just let me say , it doesn't cost much and it doesn't have major impact to place a few boulders , well placed , to move the water enough to cool and oxygenate the water enough to create occupancy.....VERY GOOD ONE STAG!!!!!