Bug Talk

By Keith Greenwell

As part of the River Watch program, WDTU has been conducting an annual macroinvertebrate sample on Clear Creek.

Clear Creek Macroinvertebrates Sampling

The sampling is typically done in the 3rd week of September at three sites in Clear Creek canyon: Mayhem Gulch since 2010 and at two sites off of US 6 near the gravel pit between I-70 and CO 119. The sampling is done in accordance to a procedure defined by US Forest Service. A volunteer shuffles his feet and scrubs rocks to dislodge the bugs and another volunteer holds a fine meshed seine net downstream for collection.

After the bugs are collected at four locations, two in fast riffles and two in slow water, we retire to the shore and pick thru the sample for visible bugs. The macro-invertibrates are preserved in alcohol and then shipped to the USFS lab in Fort Collins for an official count and taxanomic identification. The procedure at the USFS lab is to dump the sample onto a table with 15 marked grids. They then randomly select grids and count and identify the subspecies until they have counted 500 organism. This process does not give a population density but identifies the relative numbers of the different species. The number of grids needed to obtain the 500 count does give an indication of overall population density.