Lamprey Family (Petromyzontidae)

Among the most ancient types of fish.
Have no lower jaw and no bones; skeleton is made of cartilage
Breed in freshwater
Spend 3 to 7 years as filter feeding larva (ammocoetes) in sand, silt or mud bottoms before transforming into adults and emerging into the stream.
Some species spawn and die immediately after transformation
Other species are parasitic; they attach to other fish and feed on body fluids
Parasitic species live for one or more years as adults, usually in the Ocean, before returning to freshwater to spawn and die.

Identification tips

Long eel-like form
No lower jaw; mouth is a round or oval opening
Ammocoetes (larvae) have no eyes
Adults have eyes, teeth visible in mouth, a single nostril on top of the head and 7 gill openings.

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Primary Information Source:
McPhail, J.D. 2007. The Freshwater Fishes of British Columbia. University of Alberta Press. Edmonton, Alberta.