[5] As larve (ammocoetes), the northern brook lamprey are filter feeders; feeding primarily on detritus, zooplankton, algae, diatoms, bacteria, pollen and a host of other microorganisms as they remain burrowed in fine substrate in calm waters.

Males begin building nests and females lay between 1200[8] and 1524[9] eggs to combat high mortality rates of young.

[7] Once the ammocoetes emerge from the eggs 2 weeks after fertilization, they spend the next 5–6 years feeding on algae and bacteria in burrows.

It is speculated that the main reason for population decline is due to the presence of sea lamprey and the lampricides used to be rid of them.

[10] In Minnesota, northern brook lampreys are considered a special concern species as they are believed to be declining due to lampricide use and habitat degradation.

[6] The lampricide treatments are used in response to the invasive species, sea lampreys, that are currently plaguing the great lake region.