Lord of the Flies - MVIHES term for an expert in identifying aquatic bugs
Can Benthic Invertebrates (bugs that live at the bottom of rivers and lakes) provide us with a measure of the health of our watershed? Well, yes they can.
Bruce Murray, who is a MVIHES member and our own Lord of the Flies, is guiding us on a program of monitoring Benthic Invertebrates for the purpose of measuring the health of the Englishman River watershed. Since June, we have partnered with members of the Island Waters Flyfishing Club in Nanaimo to sample five sites on the Englishman River. A member of the Mid-Island Castaways Fly Fishing Club in Qualicum Beach is also participaing. It makes perfect sense that fly-fishermen would also be proficient at identifying aquatic bugs.
We are using a method of sampling that has been around for a while, and anyone who has taken the “Steamkeepers" course will remember it. We scrape rocks from the bottom of the river into fine meshed nets to capture the bugs, and then set up tables on the river’s edge, where we sort the bugs into ice cube trays (now you know where the fly in your drink came from).
Bruce then straps a microscope to his face to get a very close look at the features of the bugs to aid in their identification. Ok, so it's not a microscope on his face but it's a pretty impressive set of magnifiers. Data on the types of bugs and their numbers are recorded.
To give you an idea of how useful this monitoring can be, benthic invertebrates are classified into the following three groups based on their ability or inability to tolerate polluted water.
- Pollution Intolerant: Caddis Flies, Stone Flies, May Flies, Dobson Flies, Riffle Beetles
- Somewhat Pollution Intolerant: Dragon Flies, Damsel Flies, Crane Flies, Aquatic Sowbugs, Alder Flies, Scud, Crayfish, Clams
- PollutionTolerant: Midges, Blackfies, Backswimmers, Boatmen, Leeches, Aquatic Worms,
However, just because you have Leeches and Boatmen living in your pond doesn't necessarily mean the pond is polluted, because these guys can live under all kinds of conditions. That's what makes them Pollution Tolerant. It's when you have very few or none of the Pollution Intolerant bugs in your pond that you may have a problem with water quality.
Many thanks to Bruce, the Island Waters Fly Fishing Club, the Castaways and our volunteers.