Many kinds of animals without backbones live in and near the river's waters, and are an important part of the system.
NSRWA member Fred SaintOurs has created an electronic field guide to aquatic macroinvertebrates of small streams in eastern MA. The key includes more than 100 genera from 70 families of mayfly, stonefly, caddisfly, and dragonfly larvae, crustaceans, etc.

You can also read a report on macroinvertebrates in the North River and the methods used for the research. (Both will open in MS Word.)