Sea Lamprey

The snake-like sea lamprey is one of the most popular and amazing species seen at the Robert Barrett Fishway. It is often mistaken for an eel, but it is a completely different fish. They are a study in persistence. It is a slow swimmer, losing its eyesight, digestive system and teeth when it enters fresh water, yet intent on finding spawning grounds by using its sense of smell and touch. The juvenile sea lamprey, called ammoecetes, bury into the sandy bottom and filter feed for 5 to 7 years before floating downstream to the ocean. While in the ocean, sea lampreys are parasitic, using their disk-like mouths to attach to fish and withdraw fluids and blood. Amazingly, they grow from the size of a pencil to 30 inches long in 18 months at which time they begin the long, strenuous journey to fresh water. While traveling upstream they rest by holding on with their mouths to rocks, anglers boots, the windows of the fishway or any hard surface. However, they are not feeding while on their migration upstream. 

Fun Facts 

  • Sea lampreys have 3 eyes. The lateral eyes are going blind as they migrate upstream, but a light sensor, a white spot on top of their heads, keeps them oriented in the water column as they journey inland. 
  • The primitive breathing holes on each side open and close to pump water into their gill structures. 
  • Differences between Sea lamprey and American eels include:
    • Sea lamprey are cartilaginous fish, eels are bony fish. 
    • Sea lamprey have a disk-like mouth, eels have a hinged jaw. 
    • Sea lamprey have breathing holes, eels have gills and a gill cover. 
    • Sea lamprey have no pectoral (side) fins, eels have one pair. 
    • Sea lamprey have two fins on their backs, eels have one fin extending from the back around the tail to the stomach. 

Seasonal Contact Info

Robert Barrett Fishway
1-3 County Bridge
Holyoke, MA 01040
Tel: (413) 536-9460
Email the Fishway