Sea Lamprey
  • Side view of an adult sea lamprey.
  • Side view of an adult sea lamprey.
  • Side view of an adult sea lamprey.
  • Top view adult.
  • Bottom view adult.
  • Head-on view adult.
  • Close-up flank.
  • Close-up head.
  • Close-up mouth and snout.
  • Close-up tail.
  • Close-up dorsal fin.
  • Close-up teeth: Notice the bicuspid circumoral and the closely spaced supraoral teeth.
  • Count myomeres from the last branchial pore to the anus. Notice the separate dorsal lobes.
  • Close-up dorsal fin: The two lobes of the dorsal fin are separate.
  • There are 63-73 trunk myomeres; start myomere count past last branchial pore.
  • Close-up teeth: Notice the bicuspid circumoral and the closely spaced supraoral teeth.
  • Side view of an ammocoete (larval stage).
  • View of head of an ammocoete (larval stage).
  • Close-up mouth of an ammocoete (larval stage).
  • Close-up tail of an ammocoete (larval stage).
  • Lampreys will attach briefly but will not feed on humans.
DescriptionSimilar Species
Lampreys (Petromyzontidae)
Mouth and Snout: Sucking disk in adults, flexible hood in juveniles, no jaw. Teeth weakly developed in adults, none in juveniles. No barbels. Gill openings consist of seven circular holes. Body Pattern: Mottled color in adults, solid in ammocoetes. Dorsal side and flanks with dark brown to black mottling on lighter browning background in adults, solid dark brown or gray in ammocoetes, grading to lighter gray/brown or off-white ventrally in both adults and ammocoetes. Lateral pores unpigmented. No scales. Body Shape: Elongate, cylindrical, flexible body. Typical adult size is 350-550 mm (12-24 inches) with a maximum length of 760 mm.
Rounded tail. Dorsal fin with no spines. No anal, pectoral, pelvic or adipose fins. The dorsal fin is divided into two lobes--the posterior is continuous with the caudal fin and the anterior is separate.
Distinguishing Characteristics
Eel-like body and sucking disk identify the lamprey family. First and second dorsal fins are separate. Lateral pores unpigmented. Adults only: maximum disk diameter greater than maximum body diameter; supraorbital lamina teeth cusps close together, inner circumoral teeth bicuspid. Maximum length 760 mm. 63-73 trunk myomeres. See also similar species information.
Breeding Adults
The coloring of breeding males is richer and more pronounced, and the dorsal fins are somewhat elevated.
Ammocoete form. Distinguished from adults by head and mouth characteristics. Ammocoetes lack eyes, have a hood-like covering of the mouth without a papillary fringe, and have soft sieve-like tissue in the mouth. Juveniles are a less mottled gray/brown.
None known from Wisconsin.
Compare Similar Species
1st and 2nd Dorsal Fins
Lamprey, American BrookSeparated
Lamprey, ChestnutConnected
Lamprey, Northern BrookConnected
Lamprey, SeaSeparated
Lamprey, SilverConnected
Lamprey, Southern BrookConnected
Trunk Myomeres
Lamprey, American Brook64-75
Lamprey, Chestnut51-56
Lamprey, Northern Brook46-56
Lamprey, Sea63-73
Lamprey, Silver46-53
Lamprey, Southern Brook49-57
Lateral Pores
Lamprey, American BrookUnpigmented
Lamprey, ChestnutPigmented
Lamprey, Northern BrookUnpigmented
Lamprey, SeaUnpigmented
Lamprey, SilverUnpigmented (pigmented in large adults)
Lamprey, Southern BrookPigmented
Maximum Disk Diameter Relative to Maximum Body Diameter in Adults
Lamprey, American BrookLess
Lamprey, ChestnutGreater
Lamprey, Northern BrookLess
Lamprey, SeaGreater
Lamprey, SilverGreater
Lamprey, Southern BrookLess
Suproral Lamina Teeth
Lamprey, American BrookWidely separated
Lamprey, ChestnutClose together
Lamprey, Northern BrookClose together
Lamprey, SeaClose together
Lamprey, SilverClose together
Lamprey, Southern BrookClose together
Inner Circumoral Teeth
Lamprey, American BrookBicuspid
Lamprey, ChestnutBicuspid
Lamprey, Northern BrookUnicupsid
Lamprey, SeaBicuspid
Lamprey, SilverUnicupsid
Lamprey, Southern BrookBicuspid
Maximum Total Length (mm) in WI
Lamprey, American Brook202
Lamprey, Chestnut271
Lamprey, Northern Brook171
Lamprey, Sea760
Lamprey, Silver385
Lamprey, Southern Brook~170
Similarity Index
Lamprey, American BrookVery similar as ammocoetes, moderately similar as adults
Lamprey, ChestnutModerately similar
Lamprey, Northern BrookModerately similar
Lamprey, SeaN/A
Lamprey, SilverModerately similar
Lamprey, Southern BrookModerately similar