How to Identify American Brook Lamprey

To identify American Brook Lamprey (Lethenteron appendix), look at these key features.

Physical Characteristics

Body shape

eel-like

Coloration

Adults are typically dark brown to olive-brown dorsally, fading to lighter brown or yellowish-white ventrally. Ammocoetes are uniformly light tan to yellowish-brown.

Scale type

none

Mouth position

inferior

Distinctive features

Eel-like body without scales or paired fins., Seven gill openings (pore-like) on each side of the head., Oral disc (buccal funnel) present, but teeth are blunt and non-functional in adults., Two distinct dorsal fins, separated or barely touching, with the second dorsal fin continuous with the caudal fin., Pineal spot (light-sensitive organ) visible on top of the head.

Dorsal fin

Two distinct dorsal fins; the first is low and rounded, the second is higher and continuous with the caudal fin.

Tail fin

Slightly rounded to spatulate caudal fin, continuous with the second dorsal and anal fins.

Pectoral fin

Absent

Distinctive fins

Absence of paired fins (pectoral and pelvic fins) is a key characteristic of all lampreys.

Identification Tips

1. 1

   Oral Disc

   In adults, the oral disc is relatively small, and the teeth are blunt, non-functional, and often obscured, distinguishing it from parasitic lampreys with sharp, well-developed teeth.

2. 2

   Dorsal Fins

   Possesses two distinct dorsal fins, which may be slightly separated or barely touching. The second dorsal fin is continuous with the caudal fin.

3. 3

   Body Size

   Adults typically range from 10-20 cm (4-8 inches) in length, making them one of the smaller lamprey species.

4. 4

   Gill Openings

   Seven distinct, pore-like gill openings are visible on each side of the head, posterior to the eye.

5. 5

   Absence of Scales and Paired Fins

   Like all lampreys, it lacks scales and paired fins, giving it an eel-like appearance.

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