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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)

Largemouth bass (Micropterus salmoides)

Non-native

Largemouth bass are native to the freshwaters of the lower Great Lakes, the central part of the Mississippi River system south to the Gulf Coast and then eastward to the Atlantic Coast. Largemouth bass are a valued sportfish and have been introduced around the US and the world. In Idaho, largemouth bass typically reach lengths of 12 to 15 inches. In the southern and western portions of the US, these fish can reach lengths of over 30 inches and weights in excess of 20 pounds. Largemouth bass are largely piscivorous as adults (they eat other fish) and for this reason, they can have negative impacts on native fish species. Largemouth bass can be distinguished from smallmouth bass by looking at the upper jaw. The upper jaw of a largemouth bass extends beyond the back edge of the eye. It does not on smallmouth bass. Largemouth bass can be found in warm 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 in emergent vegetation and attracts the female to his nest. These fish can reproduce as young as three years of age and live as long as 15 years.

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