Freshwater Invertebrates

Picture of a crayfish.

Invertebrate is a term used to describe creatures that do not have a backbone, included in this group are molluscs, crustaceans, insects and plankton. The importance of invertebrates to a freshwater ecosystem cannot be overestimated. They are a major food source for many creatures inside and outside the water. Virtually every species of fish, reptile or amphibian feeds on one or more types of invertebrates at some stage in its life. Many invertebrates are small, perhaps microscopic and are not generally observed but they are important nontheless.

In addition to being a source of food for wildlife, they are a useful tool in evaluating water quality. The presence or absence of certain creatures will give a good indication as to health of a body of water such as a stream. Biologists will often test filter feeders such as mussels for chemicals such as heavy metals.

Crayfish
An important food source for fish, birds, turtles and mammals such as the raccoon. Crayfish are freshwater crustaceans that resemble a Maine lobster with smaller claws. They feed on plant and animal material that they scavenge. Generally they are nocturnal.
Scuds and other crustaceans
are an important intermediate food for small fish
Gastropods (snails)
are eaten by shellcrackers and other fish.
Mussels
are a favored food of muskrats, raccoons and very small mussels are eaten by fish such as the shellcracker. In addition mussels help to keep the water clean by feeding on suspended detritus and algae.
Aquatic Insects and Larvae
Are an important source of food to sunfish and juvenile bass.
Rotifers
Are an important food source of small fish that are too small to take other prey. Rotifers are multicell animals that are mostly microscopic. They posses a complete digestive tract and specialized organs. Omnivorous filter feeders they feed on each other sometimes.

diagram of a rotifer.

Illustration of rotifer anatomy from "Zoology for High Schools and Academies, American Book Company 1895"