Splashing In A Stream Can Be Educational

By Scott Shalaway
THERE’S no better way to cool off on a steamy summer day than to lie in the riffles of a clear, cool stream. And curious naturalists are sure to discover an amazing array of aquatic life.

Fish, crayfish, and a variety of aquatic insects such as Water Striders and Whirligig Beetles are common and familiar, but a surprising variety of other invertebrates occur in freshwater. Add a few kids, and you’ve got a great learning opportunity.

Stream bottoms teem with life. The simplest technique for collecting samples of these organisms requires two or three people. The only equipment necessary is a minnow seine or even an old window screen, a plastic bucket, and perhaps a hand lens.

The kicker stands about 10 ft. upstream from the collectors, who hold the seine. The kicker then drags his feet along the stream bottom to disturb the gravel bed. He also flips larger flat rocks that rest on the bottom. Meanwhile, the collectors anchor the bottom of the seine/screen on the stream bed so nothing flows beneath the mesh. The current carries the debris into the mesh and after a few minutes, the catch can be transferred to the bucket for examination.

The most familiar organisms will be a surprising variety of clams and mussels. Freshwater bivalves range in size from tiny (less than one-quarter inch) to 10 inches, though I’ve seldom seen any even approaching that upper limit.

Freshwater bivalves, like their more familiar marine cousins, are filter feeders. Their presence indicates clean water, but pollutants can concentrate in their body tissues so I wouldn’t recommend eating freshwater bivalves.

Gravel stream bottoms are also home to myriad species of snails and larval aquatic insects. Be sure to examine the bottom of large rocks. The flat-bodied creatures that cling tenaciously to the undersides of submerged rocks are Stonefly and Mayfly larvae.

On the tip of the abdomen of Stonefly larva, you’ll see two tail-like filaments. Larval Mayflies have three such tails. Both are indicators of clean water and ecologically essential links in aquatic food chains.

My favorite aquatic insects are Caddisfly larva. Watch a shallow area of clear water carefully or the contents of the bucket after it settles, and you’ll notice moving cylinders of tiny pebbles or small bundles of woody material. Pick up one of these cases, and you’ll discover it’s home to an insect. On one end, you’ll find the head and thorax, complete with legs. The soft tissues of the abdomen are protected by the case that surrounds it.

Unlike turtles, whose shells are part of the skeletal system, Caddisfly larva build their own house and carry it on their back. The weight of the case helps anchor the larva in moving water, and it offers excellent camouflage when the larva rests.

The materials used to make the case vary greatly. Some use sand, some pebbles, and some plant materials. Some of the pebble-users actually build a spiral case that can easily pass for a snail.

Ben Stout, an aquatic ecologist at Wheeling Jesuit University, has made a career of studying Caddisflies.

“I consider them keystone species,” he said, “because they eat the leaf litter that accumulates in streams. Caddisfly activity fuels downstream ecosystems.”

That fly fishermen appreciate the ecological value of Caddisflies is evident by the many caddis patterns they use as lures, but Stout and his former wife, Kathy, discovered an even more lucrative value of these fascinating insects.

When provided with bits of precious and semi-precious stones in Stout’s indoor lab, larval Caddisflies incorporate the gems into their protective cases. When the adults mature, they leave the cases behind, and the Stouts have beautiful insect-made cases of gold, lapis, garnet, turquoise and any other gem stones they provide. Kathy then turns them into earrings, necklaces and pins, which can sell for tens to thousands of dollars. Only a biologist could turn insects into cheap labor force. –Pittsburgh Post Gazette

EDITOR’S NOTE: To see samples of Kathy Stout’s jewelry, visit www.wildscape.com