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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.

Lampreys (Petromyzonids)

Pacific lamprey (Lampetra tridentata)


Pacific lamprey belong to a very unique class of fish known as agnaths, or "jawless fishes". Unlike any other Idaho fish, they are a predacious parasite that feeds off of live fish. Lampreys have a circular suction-cup mouth that is lined with hook-like teeth. lamprey moutha.jpg (9088 bytes)Once attached to a prey fish, lampreys use their tooth-lined tongue to rasp a hole through the skin of their prey. They are then able to feed upon blood and tissue, maintaining the flow by injecting an anti-coagulant to keep the victims blood from clotting. Perhaps equally amazing is that these eel-like fish are anadromous. Just as salmon and steelhead do, Pacific lampreys migrate from streams and rivers in Idaho to the Pacific Ocean before returning to spawn. Although they are not particularly strong swimmers, they are able to overcome tremendous natural and artificial obstacles such as waterfalls and dams by using their mouth to cling to the substrate. Although not well-documented, the number of lampreys in Idaho is known to have declined substantially in recent decades.

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