Most people don’t like sea lamprey even though they never seen one, especially up river of Bellows Falls but they know they don’t like them. Unfortunately for the most part it is the myth of sea lamprey they don’t like. The sea lamprey is non-parasitic native fish and an important part of the balance of nature in the Connecticut River.
The lamprey taxonomic name is Petromyzon marinus. Petromyzon translates roughly from the Latin into “one who suckles stone.” Lampreys are rare as fossils but it is known they are evolutionary survivors having traveled our oceans and rivers for 360 million years. They inhabit the Atlantic Ocean and the coastal rivers from Labrador to the Gulf of Mexico.
They can grow to 40 inches long. They have well-developed eyes, a single nostril on top of the head and seven gill openings on each side of their body. Sea lampreys are not an eel. They lack the bone skeleton and hinged jaw of a true eel. Adults have an internal skeleton of cartilage so unlike our usual fish they lack bones, jaws, and paired fins.
Lampreys are anadromous fish meaning they come to fresh water to spawn and their young return to the sea to grow into adults. What is important to know is that all truly anadromous fish including lamprey stops feeding when they return to freshwater. They are driven only by the spawning urge and live on fat reserves in their bodies. This is not a matter of choice but the result of dramatic internal physiological changes inside the lamprey itself. Adult sea lampreys in our river do not attack our fish.
Lampreys return upriver and follow the scent of larvae buried in the mud that were spawned in previous years to select their spawning site instead of necessarily returning to their natal stream. Lamprey eggs hatch into small larvae known as ammocoetes. They are not predators since they lack the sucker mouths of the adults. Ammocoetes burrow into the mud filtering out algae, small organisms and waste as food. The larvae will remain in the streams for up to 10 years drifting further downstream each year and eventually migrate to the ocean.
During their 3 year stay in the ocean lamprey become parasitic, rasping into the flesh and sucking the bodily fluids of fish. Lampreys have a round, suckerlike jawless mouth rimmed by cartilage, filled with rows of horny teeth and a rasplike “tongue.” Although lampreys sometimes prey on small invertebrates they are really fish predators. A fish attacked by lampreys may be severely weakened or even killed.
Part of the lamprey myth is based on the unintended consequences of human intervention that allowed the spread of sea lamprey through manmade canals into the Great Lakes and Lake Champlain. They are not a native species in the Great Lakes although a few sources claim that lampreys are native to both Lake Ontario and Lake Champlain.
Being weaker swimmers than salmon, lamprey use their mouths and eel-like bodies to swim their way up waterfalls. Selecting slower moving waters they can be seen making their way up falls by attaching themselves by mouth suction to a flat area on a stone, wiggling their bodies until they feel the flow of the water pulse and lessen and in that small window of time immediately thrust upward and attach again at a higher point on the rock face.
They build concave circular nests by thrashing their bodies to clean the sediment off the bottom and if necessary by removing one stone at a time by attaching to it through mouth suction and swimming it out of the nest. Male and female intertwine over the nest to deposit and fertilize eggs. The nest building is a hard wired instinctive activity and even if you throw stones back into the nest as they are clearing it they will just keep removing the stones until the nest meets their requirements.
There are benefits to having lamprey in our river. Lampreys transport trace elements from the ocean back upriver from whence those micronutrients originated improving the chemical balance of the river. Fish and marine mammals including seals and striped bass really like lamprey because of their high fat content and that they are easier to catch than most fish. Lamprey nests are attractive to salmon and other fish when they prepare to dig their own nests. A silt-free concave area is good for fish eggs and adult fish know it. Immediately after spawning lamprey die and like all things in nature they become the base of the food chain and life begins again as other species feed on their carcasses.
Sea lampreys have none of the prestige of salmon but their function is important in our watershed. If you want to see lampreys head to any tributary stream in early June in the lower river and look in moving shallow water for thrashing lamprey. They are helping their species and they are helping our river.
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David Deen is River Steward for the Connecticut River Watershed Council. CRWC has been a protector of the Connecticut River for more than half a century.