Rare sighting in Aberaeron harbour
As ancient specie sets out to spawn once again

On the morning of Wednesday the 4th of May two sea lampreys were found in Aberaeron harbour. This is a good sign as it is an indication that this rarely seen and protected species is still thriving in the area.

The first one was found dead by the Aberaeron harbourmaster Nigel Wells. The second one was spotted by Coed Cymru Officer Nigel Petts as it was swimming in one of the pools that form in the Harbour at low tide. The time of year and location of the lampreys suggests they were travelling up the Aeron River in order to lay their eggs further upstream. One of the sea lampreys had the golden brown almost orange colouring and black mottled back typical of adults at spawning time.

Sea lamprey swimming in Aberaeron harbour. (Photograph by A. Bianchessi / CCC)

Whether the two lampreys succeeded in their attempt to reproduce remains for us to speculate. The death of one of them need not be a signal of alarm, as it is known that sea lampreys die after they have laid their eggs.

Lampreys are anadromous animals, which means that similarly to trout, they migrate up rivers from the sea to breed in fresh water. They are amongst the most primitive of all living vertebrates, dating back some 300 million years. Like sharks they have no bones and all their skeletal structures are made up of strong flexible cartilage. They have only one nostril and no lower jaws. Instead their mouth is a sucker-like disc, which in the adults is filled with concentric rows of strong rasping teeth.

Sucker disk-shaped mouth of a lamprey showing concentric rows of teeth and the big transverse tooth.

Having to migrate through different habitats to complete their life cycle makes lampreys particularly vulnerable to man made threats. "In the British Isles the sea lamprey is absent from many northern rivers and has become extinct in a number of southern ones mainly because of pollution and engineering barriers" says Cardigan Bay SAC Officer Annalisa Bianchessi. "Luckily sea lampreys are now protected under the European Habitat Directive through the establishment of a network of Special Areas of Conservation (SACs).

The Cardigan Bay SAC has been identified as one of the sites of conservation importance for the species, mainly because it acts as a migration ground for lampreys on their way to spawn in the Teifi River". The Cardigan Bay SAC was originally developed to protect the resident population of bottlenose dolphins in the bay. However it has recently had 6 new additions to the list of features that it should aim to protect. As well as sea and river lampreys these include Atlantic grey seals, sea caves, reefs and sandbanks. The management plan of the SAC, which has been in place since 2001, is currently being updated to account for the additional features. As still little is known about the distribution of river lamprey within the Cardigan Bay area, any reporting of lamprey sightings can be useful in understanding their conservation needs. So if you happen to spot a lamprey both in a river or at sea, you can contribute towards its protection by informing the SAC Officer Annalisa Bianchessi (contact details: Ph. 01545 572139, e-mail: annalisab@ceredigion.gov.uk).

Interesting facts about lampreys:

Lampreys are anadromous animals, which means that similarly to trout, they migrate up rivers from the sea to breed in fresh water. Eel-like in shape, they belong to the family Petromyzonidae (literally stone suckers) and are amongst the most primitive of all living vertebrates, dating back some 300 million years. Although they are commonly referred to as fish, they are in fact not true fish. Like sharks they have no bones and all their skeletal structures are made up of strong flexible cartilage. They have only one nostril and no lower jaws. Instead their mouth is a sucker-like disc, which in the adults is filled with concentric rows of strong rasping teeth.

The sea lamprey (Petromyzon marinus) is by far the largest of the British lampreys and may reach a length of 100 cm (3,2 feet) and weigh up to 2,5 kg (5,5 Pound). It usually spawns in late May or June and a single female can lay up to 172 000 eggs which it will lay on stony and gravely stretches of running water. It does so after having created a crude nest by lifting away small stones with her sucker (hence the name stone sucker). After hatching, the larvae (called ammocoetes) leave the nest and drift down stream, distributing themselves among suitable silt beds where they will live for five years before transforming into adults and going back to the sea.

Having to migrate through different habitats to complete their life cycle makes lampreys particularly vulnerable to man made threats. Severe pollution in the low reaches of a stream can eliminate whole populations by preventing upstream migration and killing downstream migrants, as has happened in the Thames and Clyde Rivers. This may happen even when there may be hundreds of kilometres upstream with good water quality and plenty of good spawning and larval habitat. Similarly engineering barriers will hinder their migration by obstructing their passage upstream.