How to Identify Pacific Lamprey

To identify Pacific Lamprey (Entosphenus tridentatus), look at these key features.

Physical Characteristics

Body shape

eel-like

Coloration

Adults are typically dark blue to black dorsally, fading to silvery-white or grey ventrally. Spawning adults may become darker and develop a reddish hue. Ammocoetes are uniformly tan or brownish.

Scale type

none

Mouth position

inferior

Distinctive features

Jawless, circular, suctorial mouth (oral disc) armed with concentric rows of sharp, horny teeth., Three prominent cusps on the supraoral lamina (a plate above the mouth opening), giving it the 'tridentatus' name., Seven distinct gill openings (pore-like) on each side of the head., Absence of paired fins (pectoral and pelvic fins)., A single nostril on top of the head., Lack of scales.

Dorsal fin

Two distinct dorsal fins, separated by a small gap. The first dorsal fin is lower and shorter than the second. The second dorsal fin is continuous with the caudal fin.

Tail fin

Slightly emarginate (not deeply forked) and continuous with the second dorsal and anal fins.

Pectoral fin

Absent

Distinctive fins

Anal fin is present and continuous with the caudal fin.

Identification Tips

1. 1

   Oral Disc and Teeth

   Examine the oral disc. Pacific Lamprey have a large, circular oral disc with numerous sharp, horny teeth arranged in concentric rows. Crucially, look for the supraoral lamina (a plate above the mouth opening) which has three distinct cusps (points). This 'three-toothed' feature is key to its scientific name and identification.

2. 2

   Gill Openings

   Count the gill openings. Like all lampreys, they have seven small, pore-like gill openings on each side of the head, posterior to the eye.

3. 3

   Dorsal Fins

   Observe the dorsal fins. Pacific Lamprey possess two distinct dorsal fins, separated by a noticeable gap. The second dorsal fin is larger and continuous with the caudal fin.

4. 4

   Absence of Paired Fins and Scales

   Note the lack of pectoral and pelvic fins, and the smooth, scaleless skin. This distinguishes them from true fish.

5. 5

   Body Size

   Adult Pacific Lamprey are among the largest lamprey species, typically reaching lengths of 50-80 cm, which can help differentiate them from smaller lamprey species in their range.

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