Once the ammocoetes emerge from their embryos, they drift downstream to low velocity waters where fine substrates can be found.

[9] Ammocoetes are filter feeders that draw overlying water into burrows they dig into soft bottom substrates.

[9] Juveniles/adults have a jawless, sucker-like mouth that allows them to become parasitic on other fish and sperm whales, attaching themselves with their suckers and feeding on blood and body fluids.

Lampreys construct a nest (redd) in small gravel and females can lay over 100,000 eggs, which are fertilized externally by the male.

[12] The lower relative fecundity of the John Day River could be due in part to energy and resource cost associated with migration.

[12] Fecundity is also directly proportional to Lamprey body size meaning that environmental conditions and genetic influences could alter the fecundity of Pacific Lamprey[13][14] The cessation of feeding after migration begins also decreases body size by 18–30% altering the number of eggs spawned.

In spawning grounds, the overflow of eggs in lamprey nests are targeted by fish such as rainbow trout (O.mykiss) and speckled dace (Rhinichthys osculus).

[11] The larvae are eaten by young coho salmon (Oncorhynchus kisutch) that inhabit the same spawning and rearing grounds.

[17] They are also used as bait by fishermen who commonly use lamprey larvae to catch fish like smallmouth bass (Micropterus dolomieui).

[18] Their high caloric value and ease of capture make them a priority target over other fishes like salmon.

[15] Even in their larval stage, pacific lamprey increase the quality of life for other organisms living in stream ecosystems.

Filter feeding ammocoetes help to break down particle-borne nutrients (i.e. detritus, diatoms, and algae) into fine particulate matter which can eaten by smaller organisms.

Ammocoetes, with assistance of other small organisms, consume algae in streams and help keep riparian habitats free from algal build up.

The Yurok and Wiyot snag lampreys in the surf at the mouth of the Klamath River, often at night, using hand-carved wooden "hooks".

[19] Because lampreys are fatty and have a very high caloric count, tribes like the Wiyot and Yurok have traditionally fed them to babies and young children.

[20] The high caloric count also make lampreys an important piece of the river ecosystem, as other animals also rely on them.

Damming rivers, channelization, and declines in water quality have impacted pacific lamprey habitat and their ability to live.

The Pacific Lamprey Conservation Initiative (PLCI) emerged as a collaborative effort, comprising Native American tribes, federal, state and local agencies, as well as non-governmental organizations.

PLCI is working to achieve long-term persistence of Pacific Lamprey, and support the ongoing use for native tribes.

[29] The PLCI is composed of three components: the Pacific Lamprey Assessment, Conservation Agreement, and Regional Implementation Plans (RIPS).

[30] The second component, Conservation Agreement, is a commitment by natural resource agencies and tribes to utilize combined resources to reduce threats to Pacific Lamprey in the face of climate change, and to improve their habitats and population status, and support traditional tribal use of lamprey.

[31] A notable collaboration has emerged in the Columbia River basin where several organizations and native tribes have come together under the PLCI to implement various conservation methods.