- COSEWIC – Special concern.
- COSSARO – Special concern.
- Has the characteristic features of lampreys, a round mouth and teeth arranged in a circle, but this species is non- parasitic.
- Small (9-16 cm long) and is easily confused with other native lampreys.
- Skin leathery without scales.
- Upper body dark grey or brown and the sides are grey or silver.
- Belly orange or silver.
- End of the tail dark grey or black and the base of the dorsal fin is tan. The dorsal fin is continuous, not divided into two distinct fins and the caudal fin is oval.
- Eyes are bluish and there is single nostril between the eyes.
- As indicated by its common name, this species lives in small rivers, particularly clean headwaters of creeks and small rivers with coarse gravel to rock bottoms.
- Adults spawn in gravely riffles and then die. Individuals can lay over 1,000 eggs.
- In two to four weeks the eggs hatch into a larval stage called ammocoetes. Ammocetes then burrow into soft mud and spend from five to seven years growing in their larval burrows. The length of ammocete life is difficult to determine and probably variable depending on location and food availability. Then, they change into an immature adult stage which lasts over winter. They develop sexual maturity quickly, emerge from the mud and disperse as adults to the spawning grounds.
- Adults never feed and live for about a year before dying.
- The ammocoetes (larvae) feed on diatoms and protozoan.
- Application of non-selective chemicals to control sea lamprey likely led to their decline.
- Other threats include water draw down and siltation.
- General prohibition relating to the destruction or harmful alteration of fish habitat as outlined in the Federal Fisheries Act.
- Due to its small size, secretive life-style and non-parasitic nature, this species has received little attention.