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Sea lamprey Petromyzon marinus Linnaeus 1758


[Bigelow and Schroeder, 1948 p. 46.]

Sea lamprey (Petromyzon marinus)

Figure 3.—Sea lamprey (Petromyzon marinus). about 18 inches long, Merrimac River; and open mouth disc of another Merrimac River specimen to show the arrangement of the horny teeth, about 0.9 times natural size. From Bigelow and Schroeder. Drawings by E. N. Fischer.


Lampreys are eel-like in appearance, but have a soft, cartilaginous skeleton. They lack paired fins but have well developed dorsal and ventral finfolds. In the adult the jaws are so rudimentary that apparently they are wanting; the mouth is a longitudinal slit when closed, but forms an elliptical disk at the tip of the snout when open, and is armed with many horny, hooked teeth arranged in numerous (11 to 12) rows, the innermost the largest. There are two dorsal finfolds, and there are seven open gill slits on each side, whereas the hag has only one gill pore on each side, and only one fin. The sea lamprey (the only member of its group known from our salt waters) can hardly be mistaken for any other fish, its eel-like appearance coupled with two dorsal fins and the jawless mouth placing it at a glance.


Small specimens (whether on their way downstream or in salt water) are white below and uniformly colored above, usually described as blackish blue, or as lead colored, and more or less silvery. But large specimens usually are olive brown above, or of varying shades of yellow-brown, green, red, or blue, mottled with a darker shade of the same color, or sometimes nearly black if the dark patches are confluent. The lower surface is whitish, gray, or of a pale shade of the same hue as the ground color of the back. During breeding season, the landlocked form takes on more brilliant hues, with the ground tint turning bright yellow.


The length at the time of transformation from the larval stage is about 4 to 8 inches (100-200 mm.). Sexually mature individuals, taken [page 13] in American rivers, average 2 to 2½ feet long, up to a maximum of about 3 feet. One of 33 inches weighed 2¼ pounds.


It has been known from early times that the sea lamprey breeds in freshwater. However, it does not enter all the streams within its range indiscriminately. As an illustration, we may cite outer Nova Scotia and the Bay of Fundy, where lampreys run in the St. Marys, Sackville, Annapolis, Shubenacadie, Petit Codiac, and St. Johns Rivers, but not in the Moser or Apple Rivers, although these last also are "salmon" rivers. Their requirements are a gravelly bottom in rapid water for their spawning beds, with muddy or sandy bottom in quiet water nearby, for the larvae.

In many small streams, and in larger ones if these are blocked by dams or high falls, they may spawn only a short distance upstream; even within the influence of the tide, although invariably in fresh water. But they are able to ascend falls, if these are not too steep and high, by clinging to the rocks by their oral discs and resting. And they may run upstream for very long distances in large rivers, as they did formerly in the Merrimac and probably still do in the St. Johns River. They are still to be found 200 miles or more from the sea in the upper tributaries of the Delaware and Susquehanna systems.

Since the breeding activities of the sea lamprey take place in fresh water, a brief account will suffice here. As the two sexes ripen, the males develop a strong ridge along the back, the females a crestlike fin between the anus and the caudal fin. Spawning, commencing when the temperature of the water is about 50° F. (10° C.) is completed by the time it has warmed to about 68°-70° (20°-21° C.), and a sea lamprey has been found to contain 236,000 ova. Working in pairs, sometimes with a second female assisting, they make depressions 2 to 3 feet in diameter and about 6 inches deep in the stream bed in stretches where the bottom is stony or pebbly, dragging the stones downstream in a pile with their suckerlike mouths. And they are able to move stones as large as one's fist. It is in these depressions that the eggs are deposited, not among the piles of discarded stones that have often been described as "nests." It seems that they all die after spawning; not only have they often been found dead, but their intestines atrophy, they are attacked by fungus, and they become so debilitated that recovery seems out of the question.

The larvae are different in appearance from the adults: blind, toothless, with mouths and fins of different shape. They continue in this state for a period estimated as 3 to 4 years, during most of which time they live in burrows in the mud or sand, or hide under stones. They are abundant in the mud of flats near the mouths of small tributary streams of river systems such as the Delaware and Susquehanna, where lampreys still breed in large numbers, and they subsist on minute organisms. At the end of this larval period, when they have grown to a length of 4 to 6 inches, they undergo transformation to the adult form and structure, an event occupying about two months, August to September or October. They run down to the sea in November or December, to live and grow there for one or two years, so that large ones, not yet mature, are to be found in salt water all the year round.

Little is known of the habits of the lampreys while they live in the sea further than that their mode of life centers around a fiercely predaceous nature. Judging from their land-locked relatives and from the occasions on which they have been found fastened to sea fish, they must be extremely destructive to the latter, which they attack by "sucking on" with their wonderfully effective mouths. The lamprey usually fastens to the side of its victim, where it rasps away until it tears through the skin or scales and is able to suck the blood. Its prey sucked dry, it abandons it for another. Probably lampreys are parasites and bloodsuckers pure and simple, for we cannot learn that anything but blood has been found in their stomachs, except fish eggs, of which lampreys are occasionally full.[20]

In salt water they have been found preying on mackerel, the various anadromous herrings, cod, haddock, American pollock (Pollachius), salmon, basking sharks, swordfish, hake (Urophycis), sturgeons and eels. Sometimes as many as three or four are fast at one time to a single shad, and they are said to be exceedingly aggressive in their attacks on other fishes. Occasionally they are found fast to driftwood, even to boats. When not clinging to anything they are strong, vigorous swimmers, progressing by an undulating motion.

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General range—

Atlantic coasts of Europe and of North America; from the west coast of Greenland to Florida in the western side of the Atlantic; from northern Norway to the Mediterranean in the eastern;[21] running up fresh rivers to breed, and landlocked in certain American lakes.

Occurrence in the Gulf of Maine—

No doubt the sea lamprey occurs along the whole coast line of the Gulf of Maine, for it is recorded in or at the mouths of numerous rivers and streams in Nova Scotia, New Brunswick, Maine, and Massachusetts; specifically in the St John, Annapolis, Petit Codiac, and Shubenacadie Rivers and from the St. Andrews region in salt water in the Bay of Fundy; from Eastport, Bucksport, Casco Bay, and the Presumpscott, Kennebec, and Penobscot Rivers in Maine; from the Merrimac River system; from the Exeter and Lamprey Rivers, tributaries of Great Bay, New Hampshire; and from the Parker River in northern Massachusetts.

Since lampreys never take the hook or are captured in nets except on rare occasions they are seldom seen in salt water; only when running up our rivers are they familiar objects. But they have been taken as far offshore as the seaward slopes of Banquereau, Sable Island, and LaHave Banks off Nova Scotia; on Browns Bank; in the deep gully between the latter and Georges Bank, and over the continental slope off Nantucket and off Marthas, Vineyard.

Lampreys have long been known to run up New England rivers a little earlier in the spring than shad, perhaps beginning to work upstream as early as the beginning of April or even the end of March. In the rivers tributary to the Gulf of Maine the runs are at their peak during May and early June, with few, if any, entering later than that. The larvae have been reported by Doctor Huntsman as plentiful in the Shubenacadie (emptying into the Bay of Fundy) and no doubt they are to be found in the Merrimac system, in the Exeter River, and in other Gulf of Maine streams.


The construction of impassible dams has sadly reduced the numbers of lampreys in the larger rivers of New England. In the Merrimac, for example, once a famous lamprey river,[22] so few now succeed in surrmounting the succession of dams that a recent survey yielded no evidence of any now having access to the upper reaches. Some lampreys, however, are said to breed in the river below the Lowell dam;[23] we have seen what resembled their "nests" in the Squannacook, a branch of the Nashua tributary to the Middle Merrimac, and they still continue numerous in some Gulf of Maine streams where they can reach suitable spawning grounds without too great difficulty. We may quote catches of up to 119 recently in the Shubenacadie, where larvae also have recently been reported in abundance,[24] and of more than 100 each on several occasions in the Exeter River,[25] where they are familiar spectacles, as they gather at the falls at Exeter, N. H. But we ought perhaps to caution the reader that while lampreys, like other anadromous fishes, may seem plentiful when condensed between the narrow bounds of a river's banks, their numbers as a whole do not rival those of the more abundant of the salt-water fishes.


Lampreys were esteemed a great delicacy in Europe during the middle ages (historians tell us Henry I of England died of a surfeit of them) and considerable numbers were captured of old in the rivers of New England for human food, particularly in the Connecticut and Merrimac Rivers. But the lamprey fishery has been scarcely more than a memory for 40 years past except locally and in a small way for home consumption, or to supply the needs of biological laboratories. In the salt water of the Gulf of Maine the lamprey has never been of any commercial importance; the average fisherman might not see one in a lifetime, nor is there any sale for the few that are picked up by chance. But larvae are taken in considerable numbers for bait in the Susquehanna River, and perhaps elsewhere along the middle Atlantic coast.

[20] Goode, Fish. Ind. U. S., Sect. I, 1884, p. 677.

[21] Also reported from "West Africa" by Güther, Cat. Fishes British Museum, vol. 8, 1870, p. 502.

[22] For an account of the lamprey fishery in New England during the first half of the 19th century, see Goode, Fish. and Fishery Ind. U.S., Sect. 1, 1884, p. 680.

[23] Bailey, Biol. Survey Merrimack Watershed, New Hampshire Fish and Game Dept., 1938, p. 155.

[24] Information gathered for us by Dr. A. G. Huntsman.

[25] Collected for the Biological Laboratory, Harvard University.