Pacific lamprey grow to about 31 inches as adults. They have slender, elongate bodies with two dorsal fins arising far back on the body. Adults living in the sea are a bluish-black or greenish colour above and pale below, but those in fresh water are brown. This species is distinguished by having three sharp teeth on the supraoral bar above the mouth and three sharp points on each lateral plate.
Fun Fact Lamprey spend the majority of their lives as larvae in freshwater (3-7 years). After they undergo metamorphosis in to adults, they live for 1-2 years in sea water. Once ready for spawning they return to a freshwater stream and they die 4 days after spawning.