Sea Lamprey

by John Barker

I first became aware of the Sea Lamprey, Petromyzon marinus, after finding a dead specimen on the bank of the River Ouse in east Sussex in the late 1950s. It was a fish that I was unfamiliar with, although I had taken the Brook Lamprey, Lampetra planeri, and the River Lamprey, Lampetra fluviatilis, from the River Kennet as a boy with a hand net. These are the three British species of lampreys.


Lamprey (Photograph by Andrew Syvret)

Lampreys are primitive in evolutionary terms and resemble the very first jawless fishes that swam in the oceans. The skeleton of the lamprey is composed of cartilage (gristle); the body is cylindrical and in the Sea Lamprey can be up to 1 metre (3 foot) in length. There are seven gill apertures on each side of the head and the eyes are large. A simple nasal aperture is present on the top of the head between the eyes, the end of which does not penetrate the palate. There are two pronounced dorsal fins, separated from each other, and when breeding, a ridge of skin appears along the back of the males. The mouth is merely a round sucking disc containing rows of dagger-like teeth and a rasping tongue armed with three large teeth. The weight attained can be up to 2.2 kg (5 lb) in the females and a kilogram lighter in the males.


All three species of lamprey breed in freshwater where the larvae remain until metamorphosis. The Sea Lamprey and the River Lamprey change into adults after 5 or 6 years and make their way to the sea where they will spend their adult lives until they return to the rivers to spawn and then die. However, the Brook Lamprey will live its whole life in fresh water.

Life cycle of the Sea Lamprey

Sea Lampreys are grey or greenish, darker on the back, with darker spots and marbling. The scaleless skin is covered in mucus.

Sea Lampreys are parasitic on other fish and marine mammals: they attach themselves to their victims by the sucking mouth, and use the tongue to scrape away the flesh of their host, drinking the blood at the same time.


Sea Lamprey larvae are so different from the adults that they were once thought to be an entirely different creature and were given the name Ammocoetes branchialis. They are almost tadpole-like in shape. The mouth is devoid of teeth and is horseshoe-shaped with a broad upper lip. The eyes are rudimentary and buried beneath the skin. Ammocoetes feed on small food particles which are carried to the mouth by water currents, become entangled in strings of mucus, and are then swallowed. They spend most of their lives buried in soft mud (at the bottom of a river) until they metamorphose into the adult form. A common name for the larvae is "Pride".

Henry I

Sea Lampreys are one of the few fish reputed to have killed a King. Henry I was reported to have died in Normandy in 1135 after feeding too heartily on lampreys. I have eaten smoked lamprey in Germany and found them excellent.

River Ouse

There is a seasonal run of lampreys in the River Ouse each year starting in early May, and they migrate and attempt to swim back to the sea in mid-June. They die on their journey and none of them return to spawn for a second time.

The Sussex Ouse starts its life near Handcross in the north of the county and reaches the sea at Newhaven. Up to Barcombe Mills, around 13 miles from the sea, the river is tidal with a rise and fall that can be over 2 metres on the spring tides at Barcombe. At Barcombe Mills the river below the weirs runs off into four small streams, which owing to the strong flow of water have sand and gravel beds.

It is in one of these streams that the mating pairs start to clear their "furrow" to lay their eggs. Large stones and pebbles are seized by their sucking mouths and moved either below or above the "furrow" and the eggs are laid in the sand to which they stick and are quickly covered by sand added by the strong water flow. I have seen that the adults often replace the larger stones from the top of the furrow first. I think this is to cover the eggs quicker. Most books say that the mating pairs each have their own furrow, but I have seen up to a dozen females and five or six males working on a furrow about 140 cm long, in more of a co-operative effort between the pairs.

Barcombe Mills

In the drought of 1996 the river levels were very low and the lampreys spawned below a bridge at Barcombe Mills in less than 30 cm (1 ft) of water, much to the delight of the general public, who were able to observe them for over a week. A metre long lamprey from this stream was exhibited by the Southern Water Authority at the County Fair at Ardingly, East Sussex in 1981.

Further reading:

History of Fishes, by J. R. Norman [Ernest Benn 1931 and subsequent editions].

Fresh Water Fishes by P.S. Maitland and R.N. Campbell.


Jawless fishes, to which the lampreys belong, are very different from the bony fishes, Osteichthyes: they have no scales, no paired fins or fin rays, a cartilage skeleton like the sharks and rays, a row of separate gill-pouches which each have their own opening, and a mouth with rasping teeth but no movable jaws.

Jawless fishes evolved nearly 500 million years ago in the Early Ordovician period. Most species have died out. They flourished in a variety of forms in the Devonian period about 400 million years ago, before the sharks and bony fishes became abundant in the oceans. The lampreys and hagfishes (Myxinidae) are the only living representatives; they have fossil records going back to the Carboniferous period, some 340 million years ago, and have remained virtually unchanged since then.

Agnatha Greek gnathos = jaws a = without.

Agnatha = craniates without jaws.

Gnathostomata = craniates with jaws.

Systematics of the Vertebrates (University of Berkeley, California, USA)
  Phylum:  Chordata 
  Subphylum:  Vertebrata 
  Superclass:  Agnatha 
  Class:  Cephalaspidomorphi
  Order:  Petromyzontiformes
  Family:  Petromyzonidae 
  Genus:  Petromyzon 
  Species:  marinus 

  Common names: Sea Lamprey
                Rock Licker

  lambere = to lick
  petra = a stone

Sea Lamprey:  picture of its mouth

Fish Page

Lamprey Report

One of the most amazing reports arrived by EMail by David de la Roche whilst swimming off Folkestone, Kent, early in 1999. He felt something slippery and eel-like fasten on to his thigh. Shocked, he successfully warded off what was almost certainly a Lamprey, Petromyzon marinus, about 75 mm in diameter. It left a 25 mm bruise where the parasitic fish had tried to latch on.

Possible Lamprey Attack:
Steve Chapman (Stoke Newington) was swimming off the Camber Sands (near Rye), East Sussex, at the beginning of September 1999, when he felt a slight wasp-like sting, which was not really apparent until he left the water. The wound was on his lower leg and was small, not even finger sized, about 13 mm x 9 mm, red and sore with about 10-15 scab-like pin pricks which looked infected. After he rinsed his leg the slight sting was relieved and he was just left with a small wound. Six months later (February 2000) a white scar still remains.

The Wound on the shin. (The circle is a penny coin for size comparison.)

Forum Report

21 February 2003
Tony Heart caught a Pollack on angling tackle with a Sea Lamprey, Petromyzon marinus, attached 23 miles WNW of Corbiere, Jersey, roughly 8 miles SW of Hanois Light, Channel Islands.

The Sea Lamprey was 51.8 grams in weight and 267 mm in length. This jawless fish is still reasonably common but there are few records from the Channel Islands. In recent past they have been eaten.

Report and photograph by Andrew Syvret
on the Marine Wildlife of the North-east Atlantic Ocean Group
Original Report and Discussion (Link)
Channel Islands Wildlife Discussion Forum

It seems that the Tamar complex (Cornwall) must be a stronghold for Sea Lampreys (at least in Britain). I have had reports of redds in a tributary of the Lynher, and have seen photos from the Environment Agency of them on breeding grounds at the tidal limit of the Tamar.  We have also had an adult brought in to us that was found attached to the Torpoint ferry slipway and a 28 cm juvenile that was caught attached to a Whiting under the Tamar bridges.
Report fromDoug Herdson (National Marine Aquarium, Plymouth)
on the Marine Wildlife of the North-east Atlantic Ocean Group

24 February 2005
Sea Lamprey    Richard Lord

Sea Lamprey    Richard LordRichard Seager brought me a live sea lamprey in the late afternoon
at 5:00 pm.  It had been attached to a Bass which was caught off
Guernsey's west coast.  The lamprey is about 20 cm long.  It is in a
photo aquarium and will be returned to the sea shortly.

This is the third sea lamprey, Petromyzon marinus, which Richard Seager
has found attached to bass off Guernsey's west coast this year.

The first one he caught at Boue Blondel on 1 February.  This specimen
died in his sand eel vivier on board his boat. He gave it to me on 6
February 2005.  I attach a photo of it to this email.  It had a total
length of 18.2 cm and a total weight of 12 grams.  The seven gill
openings from the anterior margin of the first to the posterior margin
of the last measured 16.6 mm. The circular sucking disc had a width of
13.5 mm and a length of 15.9 mm.  It was preserved in 96% ethanol on 7

The second sea lamprey was caught attached to a bass on 6 February and
given to the Guernsey Aquarium where it still resides in a tank with
about five young grey mullet and one young red bream.  It has remained
attached to the aquarium glass since arriving in the tank although it
has moved around the glass from time to time.

I have only two other records for sea lamprey in Channel Island waters.
I spoke with commercial fisherman Paul Breban on 4 August 1997 and he
told me he had caught a bass with a lamprey attached to it 'a few months

Report and Photographs by Richard Lord (Guernsey)

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