Live Streaming

After so many stories from the road, this little story about one of my last events in Washington got shoved aside. I spent some time in Percival Creek with the Thurston County Stream Team conducting a stream bug survey, also known as a biological index of benthic invertebrates (BIBI). File this under “Things I wasn’t allowed to do 30 years ago”.

Stream bug monitoring is an important way to gauge the health of a stream. Some thrive in polluted water, some thrive in pristine water. To know how many of which kinds of insects are in the stream is a good indicator of water quality. Just what is a stream bug? The ones we looked for are actually the larvae of insects such as mayflies and caddisflies. The larvae are aquatic, living in freshwater, making a living in a variety of ways such as scrapers and shredders.

The method used by my group was to sample three areas within a riffle of the stream. A riffle is an area of faster moving water. Our leader, Debbie Smith, is the coordinator for Tumwater Stream Team. She supplied us with all the necessary equipment, minus our own boots. To collect samples, we used a funnel-shaped net that had a metal square at the front which marked the boundary of the sampling area. A weed fork is a great tool for the stream to, scaring up bugs on the rocks and in the substrate by rapidly mixing it around inside the metal square. Debbie also brought a stop watch, buckets, insect field guides, and lab equipment including magnifying glasses, headlamps, forceps, and sealed containers. While we began collecting samples, Debbie stayed behind with one other from our group to set up the lab. 

Net similar to the one we used for sampling. The front section defines the sampling area.

Weed fork

After washing our boots in a mild chemical solution, we took turns mixing up both the surface and substrate of the stream bed for a minute, loosening the bugs which then flowed into the net with the current. Large rocks in the square went into a bucket for analysis. Stream width and depth at the sample sites, as well as the length of the sampled riffle, were recorded for each sample. Distilled water (to prevent outside bugs from being counted in the sample) was used to rinse any bugs on the net into the collection bag at the bottom. 

Example of stream bugs clinging to a rock

Processing samples in the lab (Debbie Smith photo).

Our samples were taken to the lab for analysis. Our lab was a simple setup on a bridge that day. Small rocks in the collection bag were removed and inspected. Any bugs were removed with forceps and placed in alcohol for later analysis by entomologists that can ID them by genus and species. The same was true for the large rocks in the bucket. The collection bag was emptied and scoured for bugs. Rocks were not sent to the entomologists, but any organic matter in the net, such as leaves and woody debris, did go along with the insect samples. We did this at three different riffles, for a grand total of nine minutes of churning up creek bed.

We did our survey in because stream levels are low. If the water is too high, the bottom is unreachable and the current can be dangerous. There were always at least four of us in the water: one holding the net, one using the weed fork, one running the stopwatch, and one holding the bucket of rocks. If anything happened to one of us, there was always someone available to help. Always think safety in the lab and in the field. 

Stream Team following a successful morning of splashing around
Percival Creek. I am 4th from the left in the green shirt.
(Debbie Smith photo)