critters" is how Stream Teamers describe the capture of small creatures
that live on the stream bottom.
After counting them, they return them to the water.
The object is to find out how many individual
creatures live on a 36-inch square of streambed at a "riffle." A riffle
is a swift, shallow section of a stream where many creatures live.
The movement of the water keeps it fresh and aerated. It is where
the larvae, the immature form of many water bugs and flies,
like to live. The cleaner the water, the more creatures and their
larvae will be found. It is a fun and easy way to find out how clean
the water is.
Water-dwelling larvae are numerous. Fish
eat both the larvae from the stream bottom and the adults they become.
Many critters can only live in very healthy water. Other kinds can
survive even in polluted streams. When the Stream Teamers find mostly
the kind that can live only in clean water, they know their stream’s
water is healthy. When they find only the critters that can live in
polluted water, it is time to worry.
On March 22, 2000, Debra, Susan, Marion and Peter were
“doing critters.” They got out the net, found a nice riffle and anchored
the bottom of the net with stones and gravel so the moving water would
flow into the net.
Debra and Susan brushed the larger stones with their
hands to remove any creatures living on them. While Peter held the
net, they stirred the square yard of stream bottom in front of the
net with their feet. The water carried all this debris into the net.
Then Debra carried the net full of critters to the riverbank.
Debra and Susan washed the critters off the net into
a white pan so they could see them better.
Debra carried the pan full of critters and algae (small
water plants that live on the stones along with the critters) to the
Everybody sat around the table and sorted the critters
they found in the white plastic pan. They used tweezers and ice trays.
Different critters went in different sections of the ice trays. That
way they kept the critters separate and could count how many there
were of each kind.
Some of the larvae were tiny, especially the youngest
ones. To identify them Peter used a magnifier, which held the tiny
creature in a few drops of water while being identified.
In this tray you can see mayfly larvae in the upper right section.
Black fly larvae are in the lower section, and a large Dobsonfly
larva (hellgramite) is in the first from the left.