Adult Mayfly: The mayflies that we find when we do a stream monitoring are the nymphs which live in the water feeding on algae and decaying matter. After a period of growth, the nymphs molts into spinners and emerge from the water to mate and the cycle continues. Photo by Keith Roragen.
It doesn’t take much to get our team of stream monitors excited and this month it was finding an Ameletid minnow mayfly at our spring monitoring of the Little Falls Branch. While small minnow mayflies regularly show up in our nets, this is our first recorded sighting of the combmouthed minnow mayfly, characterized by the unique comb-like structures on their mouths. These mayflies are usually found in very clean, cool running mountain streams. We’re not sure how it got here, but we are happy that our creek is able to support it.
Our stream monitoring team nets for benthic macroinvertibrates four times a year (winter, spring, summer, and fall.) These nettings give us a very good picture of the biological health of the creek. By assigning a pollution tolerance number to each species as well as taking into consideration the total diversity of species found and total number, we are able to compute a score for the creek that indicates it’s overall health - a Benthic Indicator of Biological Integrity or BIBI Score. ) The scores range from 0 to 5. The Little Falls Branch score for this season was 2.4, just into the Fair category (2.0 - 3.2). Interestingly, we seem to see a score of 2.4 in the spring with the score falling during the rest of the year.
Learn more about our stream monitoring efforts HERE.
Notes from the Field:
Thanks to my faithful crew of Averill, Emily, Colette, Maria and hopefully a new member - Tabatha Cutler for running an efficient spring monitoring. We dodged a thunderstorm, but overall conditions were good.
The good news: we found a Ameletid minnow mayfly and salt PPM was 92 - less than 100 is "good" for us. The bad news: our diversity of macroinvertebrate families was down
Cylindrical leeches - 2
Aquatic worm - 1
Planaria - 5
Asian clam -1
Aquatic sowbugs - 9
Chironomidae (midges) -12
Black fly - 18
Common netspinner - 17
Ameletid minnow mayfly - 1
Small minnow mayfly-Baetis - 35