What is a freshwater macroinvertebrate?
Let’s break down the term. “Macro” means big (or big enough for us to see without using a microscope) and “invertebrate” means without a backbone. So a freshwater macroinvertebrate is a small animal, without a backbone, that we can see with our naked eye. Many of these creatures make their homes in rocks, leaves and sediment in stream beds. Some spend their entire lives in water, like scuds, clams, mussels and snails. However, for most insects the larva and nymph stages (the young stages of insects’ lives) are spent in water and the adult will spend its life out of the water.
Water quality studies in the Dungeness River at Railroad Bridge Park have turned up many such creatures. Insect larvae such as stoneflies, mayflies, and caddisflies are associated with relatively clean water with lots of oxygen, suitable for fish such as salmon and trout.
Most insects found in the river are in immature stages. These “immatures” are either described as “larva” or “nymph,” which are truly different from each other. A nymph is an immature stage that is basically similar to the adults in shape and structure, just smaller and not old enough to reproduce. A larva is an immature stage that differs greatly from the adult. The insect forms listed below have been found in the Dungeness by screening or netting. Other organisms are possible, but not all are confirmed.