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What is a Macroinvertebrate?
 “Invertebrate” means
without a backbone and “Macro” means large – able to be
seen without the use of a microscope.
Common stream macroinvertebrates include mayflies, stoneflies,
caddisflies, mussels, crayfish, and snails.
Why are Macroinvertebrates Important?
 Macroinvertebrates are
important in the aquatic food chain – fish food, which also makes
them important to fly-fisherman. But
they are also great indicators of stream water quality. In fact, where a water sample can give
you a snapshot view of water quality and fish can escape from small amounts
of pollution – macroinvertebrates can provide information about
pollution that is not present at the time of sample collection. The type of macroinvertebrates present
can even indicate the type of pollution that has occurred in the past.
Macroinvertebrate Sampling
Macroinvertebrates
are relatively easy to collect. They
are found on rocks, woody debris, and stream sediments within the
creek. To collect them, however, you
need a fishing license and a collector’s permit. Please visit http://www.fish.state.pa.us/education/collinfo.htm
for more information on obtaining the appropriate permit.
Macroinvertebrates Role in Water Quality
 Indicators of Good Water Quality
– most mayflies, stoneflies, caddisflies, planaria, gilled snail,
water penny, and hellagramite.
Indicators of Good
or Fair Water Quality – most crayfish, alderflies, craneflies,
sowbugs, damselflies, scuds, dragonflies, and mussels.
Indicators of Poor
Water Quality – most leeches, lunged snails, aquatic worms, and black
flies.
The absence of good water quality
indicator species can tell you that you may have a pollution problem. An easy test of water quality is to count
the number of mayflies, stoneflies, and caddisflies in your sample. This is also called the EPT taxa index,
named after their scientific names.
The higher the EPT score, the better quality stream you are
sampling.
Macroinvertebrates in the Shermans Creek Watershed
SCCA volunteers
conduct macroinvertebrate sampling occasionally at their stream sampling
sites to gain a picture of changes in water quality seasonally or from year
to year. Check back soon for
macroinvertebrate sampling results in our watershed! SCCA has done many educational programs
about macros over the years...some of the locations or events that included
a SCCA macro demonstration are Amish & Mennonite schools in Blain,
Susquenita Elementary Earth Day, Kids Creek Day event at Carroll Township
Park as well as the County Envirothon.
 Easy to Use Macroinvertebrate Key
A
PRINTABLE POND AND STREAM STUDY GUIDE WITH KEY TO MACROINVERTEBRATES
Want to Know More?
Here are some great
links on using macroinvertebrates as water quality indicators and links to
help you identify macroinvertebrates you found in your creek.
Virginia
Save Our Streams (based on the methods from the Isaac Walton League of
America)
Buglopedia
Stroud Water Research Center
EPA Biological
Indicators of Watershed Health
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