10 April 2017

Study: Lamprey in the Liffey Channel/ April 2017

Dublin Port Company are undertaking a programme to monitor the movement of river lamprey in the Liffey Channel as part of the Alexandra Basin Redevelopment Project in the interest of wildlife protection and to broaden scientific knowledge of this elusive species.

Lamprey is classified as a fish but lack paired fins and possess a circular sucking disc instead of jaws They have a single nostril and seven small breathing holes on either side behind the eye.

Adult river lampreys measure from 25 to 40 cm. The very elongated body is a uniform dark grey above, lightening to yellowish off-white on the sides and pure white below. It feeds similar to a parasite, clinging on to the flanks or gills of larger fish with its sucker and rasps at the tissues below.

Its reproduction cycle is similar to that of a salmon. River lampreys migrate upstream from the sea to spawning grounds in autumn and winter. Spawning activity is greatest in the springtime and after spawning, the adults die. The young larvae, known as ammocoetes, spend several years in soft sediment before migrating to the sea as adults. It is thought that these fish spend two to three years in marine habitats before making the return trip to spawn.

Based on previous survey data collected by Inland Fisheries Ireland (IFI) in the Lower River Liffey, sampling took place during the dark phase of the moon, which is the time when research indicates that river lamprey is most likely to migrate upstream.

The results are very encouraging with the capture of our first lamprey in February 2017 providing solid evidence of their presence and an indication of an improving healthy ecology. The captured lamprey was safely returned to the waters of the Liffey Channel unharmed.