A. The key to this growth doesn't have as much to do with the large numbers of insects present, but with the fact that if environmental conditions remain essentially constant, as they often do in tailwaters, then the fish can continue to grow. In a normal stream, growth is cyclical depending on water temperatures. When the water becomes cold, movement, feeding, and metabolic activities slow down; the reverse happens when waters warm up and this is the time these populations grow. In tailwaters, the populations are usually acclimated to fairly constant water conditions throughout the year and thus can continue to grow as long as there is sufficient food. Fortunately, the same thing happens to the insects. Many midge and other insect species can continue to produce cohorts throughout the year if water temperatures do not go to low; thus, a continued supply of food for the fish. Thus, it isn't so much a case of large numbers of insects, it is the fact that their production rate is high and population turnover rapid.

You might want to refer to previous columns in reference to predicting insect hatches. In constant temperature waters, especially if they are on the warm side, an insect can attain the requisite number of degree days quicker that under natural conditions and crank out more cohorts per year.