What Lives in Rivers & Streams?

Updated November 21, 2016

Clean rivers, streams, creeks and brooks are full of life. They hold bounties of fish, insects, plants, amphibians and crustaceans. A river is a body of water that flows from higher to lower ground and down to the sea, generally. Stream is a rather vague term for moving water that, contrary to popular belief, doesn't have much to do with size. Rills, rivulets, brooks and creeks are small streams.


Hundreds of species of fish either visit rivers to spawn or live in them year-round. Pacific salmon make dramatic runs up rivers to breed -- the young salmon return to the sea. The Atlantic salmon also returns to streams to spawn, but unlike the Pacific salmon it doesn't always die immediately afterward. Catfish are known for living in warm, fresh water in clear, swift streams. Pikes, pickerels and muskellunge live in streams of the central and eastern United States and are valued as game fish. The muskellunge can grow to between 2 and 7 feet long and can weigh from 4.54 to 9.07kg. The smaller mosquito fish, killifish, darters and minnows also live in streams and eat insect larvae, crustaceans and small water plants.


The larvae of dragonflies, damselflies, mayflies, stone flies, black flies and caddis flies live in the water until they leave it to become adults. Dragonfly larvae are predacious in streams. Mayflies like to lay their eggs in large rivers, where their larvae eat plant debris. But not all insects who live in the water are larvae. The spotted water beetle, which can be .43 to .51 inches long, lives in slow streams in Arizona and California. It breathes air, but when it dives it creates a bubble of air around itself. Both the adult beetle and the larva are predators. The European water spider also lives in quiet streams and creates a bell of air around it when it dives. Crayfish live at the bottom of streams.


The tadpoles of frogs, toads and some salamanders live in streams as they mature into adults. At first they breathe through gills but gradually develop lungs and spend less and less time in the water. However, the mudpuppy is a large aquatic salamander that never leaves the larval stage and always has red gills. The size of the gills tells something about the condition of the water. If the mud puppy's gills are big and bushy the water is low in oxygen. If the water is oxygen rich, the gills are small.

Aquatic Plants

Pickerel weeds grow in the east in sluggish streams. They grow to 1 to 3 feet tall and have a spike of beautiful blue violet flowers. The seeds are eaten by ducks. Eelgrass is a long, straplike plant that can grow abundantly in streams and small rivers. The forests of eel grass can be a haven for fish fry, small crustaceans and microorganisms.

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