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Fishes of Idaho

How are your identification skills? Do you know which are native and which were introduced? To see photos and descriptions, and learn more about Idaho fish, check out our Fishes of Idaho online database.

There are around 20,000 species of fish in the world. About 58% of these are marine (saltwater) fish, 41% are freshwater fish, and 1% are both. We have around 100 species in Idaho, and the list keeps growing as more non-native fish are released into Idaho waters. There are only 39 species of fish native to Idaho. The rest were introduced--some by accident, but most on purpose.

Sunfishes (Centrarchids)

Smallmouth bass (Micropterus dolomieu)


Smallmouth bass are native to the freshwaters of eastern central North America. Smallmouth bass are a valued sportfish and have been introduced around the US and the world. In Idaho, smallmouth bass typically reach lengths of 10 to 15 inches. In the southern and portions of the US, these fish can reach lengths in excess of 20 inches and weights in excess of 10 pounds. Smallmouth bass are largely piscivorous as adults (they eat other fish) and for this reason, they can have negative impacts on native fish species. Smallmouth bass can be distinguished from largemouth bass by looking at the upper jaw. The upper jaw of a smallmouth bass does not extend beyond the back edge of the eye. It does on largmouth bass. Smallmouth bass can be found in cool lakes and slow moving rivers and typically spawn in late spring to early summer. Unlike trout and salmon, the male prepares the nest for the eggs over the sandy or rocky bottom of a lake or river and attracts the female to his nest. The male will guard the nest and young after they hatch. These fish can reproduce as young as three years of age and live as long as 15 years.

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