The cold water releases may have been triggered by this past week's weather. Once the water temp in the tail-race hits 68 deg F three mornings in a row at 8AM the releases start. The amount of cold water released from the bottom and mixed with the warmer "surface" water is determined by the temperature in the tail-race. The 8 AM objective is 68 deg F and the amount of bottom water released is the amount that is necessary to meet that objective. Remember, however, that if it is 68 deg in the tailrace (USGS gauge located 20% of the way down through the DH Area) is probably warmer farther downstream, especially on warm days/nights under lower flows and with the wide and sluggish or wide and shallow areas through which the stream flows in spots.
Sixty-eight degrees is the temperature at which the cumulative effects of temperature stress begin for rainbows and this is probably very similar for browns. It is probable that C&R stress adds to the temp stress. Research has revealed that temperature stress accumulates with every 15 minute period in a month that water temp exceeds 68 degrees F. Heat related mortality increases with the increasing number of 15 minute periods to which the fish are exposed. Given the naturally varying sensitivities of individual fish, when fish begin to die at temps below the maximum tolerated they don't all die at once, but do so gradually. This is probably part of the reason why anglers in many waters often say " but I never see any dead fish."
As for C&R handling at this time of the year in particular, play them quickly, unhook trout in the water (good practice anytime), and release the trout in light to moderate current, not dead water close to the stream's margins. Some trout may need an assist by holding them head forward in the current for a few seconds to a few minutes. If you are catching fish from an area that is a coldwater refuge, then release them back into the cold water, not into the near-by warmer water.
The alternative is to keep a few for dinner, which with respect to DH Areas, is suggested by the very title of the program and with the knowledge that most of the streams in the program warm up to stressful or lethal levels. Allowable DH Area harvest starts on June 15 (3 trout creel limit, 9" length limit).
