Least Brook Lamprey
• Family: Petromyzontidae (Northern Lampreys)
• Other Names: Lamprey
• Ohio Status: No special status
• Adult Size: Typically 4-6 inches, can reach 7 inches.
• Typical Foods: Organic matter and microscopic organisms.
All lampreys have a long eel-like body and no scales. They have segments of muscles that are visible along their body called myomeres, and a jawless mouth. In larval lampreys, called ammocoetes, their mouth is not fully developed, very small, and hidden between folds of skin. Adults have a disk shaped mouth with varying amounts of teeth depending on the species. The least brook lamprey has a deeply notched dorsal fin, separating it into two distinct parts. They have 54-62 myomeres (muscle segments) between the last gill opening and the anus. The disc like mouth of the adults contains large teeth only in the center. Any teeth on the outer portion of the disc are very small and difficult to see. Adults are dark tan above and lighter below prior to spawning. During spawning, adults become blue-black in color. The least brook lamprey is most similar to the American brook lamprey and sea lamprey in Ohio. The sea lamprey is much larger reaching an adult size of as much as 25 inches and is a light brown with darker speckles or blotches. Both the Ammerican brook and sea lampreys have more than 62 myomeres between the last gill opening and the anus. All other Ohio lamprey species have only a single long dorsal fin.
Habitat and Habits
All non-parasitic lampreys required two distinctly different habitats that are connected by free flowing (free of dams) stretches of streams. Adults are found in clear brooks with fast flowing water and either sand or gravel bottoms. Juveniles or ammoccoetes are found in slow moving water buried in soft substrate of medium to large streams. The least brook lamprey is native to the Ohio River drainage. Least brook lampreys are Ohio's most common lamprey. In some areas, such as the hocking hills region, large spawning groups can be witnessed in very small rocky streams in the spring.
Reproduction and Care of the Young
The least brook lamprey spawn in March and April in shallow pits that are excavated near the upper ends of gravel riffles. These pits are created communally with as many as 20 individuals constructing one pit. They use their suction cup like mouth to move stones away to form the pit. A single female can deposit as many as 1,100 eggs. After hatching, the ammocoetes (larval stage of lampreys) burrow into the sediment. During this phase, the least brook lamprey eat organic particles strained from bottom sediments and the water, as well as microscopic organisms. After at least three years, the ammocoetes transform into a non-parasitic adult in the late summer or fall. Adults remain in the smaller streams and do not feed. The following spring they spawn and then die shortly after.