How to Identify a Freshwater Fish

Updated May 23, 2018

Freshwater fish can be identified by observing a number of different features. Freshwater fish species are numerous, and it is important to know the most prevalent in the area you are fishing. This allows the angler to choose the best baits for a successful catch. And knowing the species allows the angler to determine which can be kept (and are tasty and safe to consume) and which must be released. The fish and game departments in most states provide a guide to species identification in their state regulations handbook. Identification is the first step towards understanding the species and the environment in which they reside.

Check the mouth of the fish. Sucker fish, whitefish and carp all have small, round mouths designed to suck food from the bottom of the river or lake. Bass have a large mouth that is designed to inhale large food items. Pike have a long mouth that is heavily lined with teeth. Trout, salmon and steelhead have a pointed designed to sip food and clamp on prey.

Check the colour patterns. Every species has unique colouration with slight variations based on different phenotypes. Trout are heavily spotted although some rainbow trout can be silver with spotting on the back. Chinook salmon have large spots on the back while silver salmon have small spots on the back. Carp and many sucker fish have a golden colour while sunfish vary by subspecies.

Know the habitat you are fishing. Cold waters are home to trout, salmon, steelhead, pike, muskie and a variety of other species while warm waters are home to bass, panfish such as bream, perch and crappie, and catfish and carp. Knowing the type of water eliminates a large number of species from the identification chart.

Use the fish and game resources to determine the species that are in a particular body of water. The department conducts creel surveys and electro-shocking surveys to determine the species and fish counts in the body of water.

Carry your fish identification chart on each fishing trip. Use the chart for reference if you cannot identify a species.


Research pictures of freshwater species before you go fishing. Take pictures of the fish you catch and make comparisons with the charts to learn the specifics of each species.


If you are not sure about a species, release the fish immediately. Some species are endangered and protected by law.

Things You'll Need

  • Fish and Game handbook
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About the Author

Zach Lazzari is a Montana based freelance outdoor writer and photographer. You can follow his work at