Lampreys are both peculiar and rare
Lampreys are peculiar fish in that, unlike the regular fishes that everyone is used to, they have no scales, no mouth, no bones and no gill covers. They do however have nice, meaty flesh and have consequently been a delicacy in fine dining since Roman times.
The present Queen Elizabeth ll of England is reported to have had lamprey pie at the dinner held to celebrate her coronation in 1953. Eating lampreys nowadays is frowned upon as they have become rare and are protected species under European Union and Irish law. We have three species of them in Ireland: the Sea Lamprey, the River Lamprey and the Brook Lamprey.
The Sea Lamprey is the biggest of the trio. It is Eel-like in shape and size, is mottled dark and light browns in colour and like the Eel it has no scales. Unlike the Eel it has no jaws or mouth. Instead it has a sucker-like opening under its head armed with rows of inward-curved teeth. The image above shows it holding onto a stone using its sucking mouth.
It has no hard bones; its skeleton is made of soft bone or cartilage like our external ears. And it has no regular gills and gill covers; instead it has a line of seven holes running back from each large eye. It breathes through these unprotected gill pores.
Adult Sea Lamprey live in the sea as external parasites on fish. They use their sucking mouths to hold on to the side of their host fish, use their teeth to penetrate the host's flesh and feed by sucking the host's blood.
In spring they stop feeding, leave their hosts and migrate into our large river systems to spawn in gravel far inland. Males move gravel with their mouths to excavate a redd or spawning nest. When the redd is ready the males attract females to lay in it and they fertilise the eggs as the females lay. They die after breeding.
The youngsters drift downstream until they find a bed of fine sediment to burrow into where they may live for years feeding on whatever the river current brings their way. When mature they migrate down to the sea to parasitize sea fishes.
Inland Fisheries Ireland has confirmed that some Sea Lamprey don't migrate and live land-locked in our larger lakes like Lough Derg on the Shannon, Lough Conn in Mayo, Lough Corrib in Galway and Lough Gill in Sligo.