Cover photo credit: University of Michigan Museum of Zoology, Fish Specimen Image Collection


Special Concern

“Special Concern” means the species lives in the wild in Ontario, is not endangered or threatened, but may become threatened or endangered due to a combination of biological characteristics and identified threats.

Date added to the Species at Risk in Ontario List

The Northern brook lamprey was already assessed as a species of special concern when the Endangered Species Act took effect in 2008.

What it looks like

The Northern brook lamprey is a small, elongate fish that grows to a maximum length of 16 centimetres in Ontario. It has an eel-like appearance and the characteristic features of a lamprey including a round, jawless mouth with teeth arranged in a circle and seven gill openings and no pectoral or pelvic fins . It is very difficult to distinguish this species from the other native lamprey, but biologists rely on its small size, continuous dorsal fin, and the teeth.

Adults are dark greyish-brown on the back and sides, with pale grey or silvery white on the belly.

The Northern brook lamprey has two stages of development – larval and adult. When the eggs hatch, the larvae, called ammocoetes, make burrows in soft mud and spend about six years growing. Once developed, they emerge in the spring from the sediment and disperse as adults to the spawning grounds. They die shortly after spawning has occurred.

Where it lives

The Northern brook lamprey inhabits clear, coolwater streams. The larval stage requires soft substrates such as silt and sand for burrowing which are often found in the slow-moving portions of a stream. Adults are found in areas associated with spawning, including fast flowing riffles comprised of rock or gravel.

Spawning occurs in May and June. The males construct small, often inconspicuous, nests by picking up pebbles with their mouths and moving them to form the rims of shallow depressions. The sticky eggs are deposited in the nest and adhere to the substrate.

Where it’s been found in Ontario

The Northern brook lamprey lives in the eastern United States in the upper Mississippi and southern Hudson Bay drainages, ranging from Manitoba and the Great Lakes region south to Missouri, and east to the St. Lawrence River in Quebec. In Ontario, it lives in rivers draining into Lakes Superior, Huron and Erie, and the Ottawa River.

map of northern brook lamprey range

View a Larger version of this map (PDF)

What threatens it

The use of lampricide for the control of the invasive Sea lamprey has likely contributed to declines in Northern brook lamprey populations around the Great Lakes where the two fishes coexist. Additional threats to the Northern brook lamprey include pollution and changes in water levels and temperature.

Action we are taking

Special concern species do not receive species or habitat protection.

What you can do

Report a sighting

Report a sighting of an endangered animal or plant to the Natural Heritage Information Centre. Photographs with specific locations or mapping coordinates are always helpful.


Volunteer with your local nature club or provincial park to participate in surveys or stewardship work focused on species at risk.

Be a good steward

  • private land owners have a very important role to play in species recovery; you may be eligible for stewardship programs that support the protection and recovery of species at risk and their habitats
  • land owners can help improve fish habitat and keep Ontario’s water safe and clean by maintaining natural vegetation next to creeks and rivers, and keeping pollution and soil from washing into Ontario’s rivers; you can find more information about programs and funding assistance for eligible farmers from the Ontario Soil and Crop Improvement Association website.

Report illegal activity

Report any illegal activity related to plants and wildlife to 1-877-TIPSMNR (8477667).

Quick facts

  • unlike some other lamprey species, the Northern brook lamprey is non-parasitic and does not attach itself to larger host fish; the larvae are filter-feeders, consuming microscopic plant and animal life and decaying matter; adults have a non-functional intestine and do not feed
  • multiple adults may spawn in the same nest, and multiple males may spawn with the same female; female Northern brook lamprey can lay over 1,000 eggs
  • lamprey species are one of the most ancient freshwater fish families in the world
  • lampreys are similar to sharks in that they do not have bones, but rather a cartilaginous skeleton