The Brook Lamprey (Lampetra planeri) is a small, jawless fish with an eel-like body, typically reaching about 12 inches in length. Unlike its parasitic relatives, the Brook Lamprey is n... The Brook Lamprey (Lampetra planeri) is a small, jawless fish with an eel-like body, typically reaching about 12 inches in length. Unlike its parasitic relatives, the Brook Lamprey is non-parasitic and feeds on organic matter in the sediment during its larval stage. Found in clear, cool streams and rivers, this species is an important indicator of water quality. They have a simple life cycle, with adults dying shortly after spawning.Click here to read more about Brook Lamprey.