Jun 152012
 

 

Snoqualmie River stonefly nymph

Snoqualmie River stonefly nymph

Last Saturday, my fly fishing club hosted a seminar about aquatic insects. Fly fishing flies are intended to imitate the natural foods of fish in the wild. Thus, knowing how to identify insects and understanding their habitat and lifecycle are critical in improving a fly fisherman’s fly selection skills.

Collecting aquatic insects with a fine net

Collecting aquatic insects with a fine net

We collected samples of insects (and other creatures) along the banks of the Middle Fork of the Snoqualmie River near North Bend, WA. First, we placed a long-handled fine net downstream of our feet. Then, by gently kicking the gravel upstream from the net, we disturbed the habitat of insects along the bottom causing them to float downstream into our net.

We were astounded by the sheer number and diversity of aquatic insects and other life we collected in only 20 minutes. Several samples yielded hundreds to thousands of tiny bugs.

We found large numbers of insects, worms, and small fishes. Insects of particular importance to fishermen that we caught included the pupal and nymphal stages of caddisflies, mayflies, and stoneflies.

It was quite a kick to examine the insects under a dissecting microscope. Their eerie-looking body parts would be great inspiration for the costume designers of the next “Aliens” movie.

Diversity of insects and other life in Middle Fork Snoqualmie River

Diversity of insects and other life in Middle Fork Snoqualmie River

Biologists often sample rivers for aquatic insects to determine the health of the body of water. Typically, a large diversity of insect species is an indicator that a river is healthy. On last Saturday, the  Middle Fork Snoqualmie River was a very healthy river.

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