1095 Sea lamprey Petromyzon marinus
Description and ecological characteristics
The sea lamprey Petromyzon marinus is a primitive, jawless fish resembling an eel. It is the largest of the lampreys found in the UK. It occurs in estuaries and easily accessible rivers, and is an anadromous species (i.e. spawning in freshwater but completing its life cycle in the sea). Like the other species of lamprey, sea lampreys need clean gravel for spawning, and marginal silt or sand for the burrowing juvenile ammocoetes. Sea lampreys have a preference for warm waters in which to spawn. Features such as weirs and dams, as well as polluted sections of river, may impede migration to spawning grounds. In comparison to 1099 River lamprey Lampetra fluviatilis, sea lampreys seem to be relatively poor at ascending obstacles to migration, and are frequently restricted to the lower reaches of rivers.
European status and distribution
The sea lamprey Petromyzon marinus occurs in estuaries and easily accessible rivers over much of the Atlantic coastal area of western and northern Europe (from northern Norway to the western Mediterranean) and eastern North America. It has declined in some parts of its European range.
UK status and distribution
The sea lamprey Petromyzon marinus is reasonably widespread in UK rivers. In some places it is still common, but it has declined in parts of its range and has become extinct in a number of rivers. It appears to reach its northern limit of distribution in Scotland and does not occur north of the Great Glen.
Site selection rationale
Sites with reliable records of sea lamprey Petromyzon marinus, and which contain the necessary habitat requirements for spawning and survival of juveniles, have been selected. The SAC series encompasses the geographical range of the species and includes a range of high-quality river types in which it occurs. Rivers with significant barriers to migration have been excluded. Marine sites that are considered important migration routes or feeding grounds for this species have also been selected, usually where they are adjacent to a freshwater site. Identification of suitable sites in some parts of the UK has been hampered by the absence of comparative population data. While the SAC series makes a contribution to securing favourable conservation status for this Annex II species, wider measures are also necessary to support its conservation in the UK.
Dorset and Somerset, Gloucestershire, Wiltshire and Bristol/Bath area, Hampshire and Isle of Wight
The Avon represents sea lamprey Petromyzon marinus in a high-quality river in the southern part of its range. There are excellent examples of the features that the species needs for survival, including extensive areas of sand and gravel in the middle to lower reaches of the river where sea lampreys are known to spawn.
River Derwent and Bassenthwaite Lake
The Derwent represents sea lamprey Petromyzon marinus in a high-quality oligotrophic river in northern England. The extensive occurrence of gravels and silts in the middle to lower reaches of this river means that it is able to support a large population of sea lamprey.
Cumbria, North Yorkshire, Northumberland and Tyne and Wear
The Eden represents a sea lamprey Petromyzon marinus population associated with an extensive river system on a varied and base-rich geology in northern England. The highly erodible nature of the rock results in extensive areas of gravel and finer silts being deposited throughout the system, providing conditions for spawning and nursery areas. A large and healthy population of sea lamprey is supported in the middle to lower regions of the river.
Eastern Scotland, Highlands and Islands
The River Spey represents the sea lamprey Petromyzon marinus in the northern part of its range in the UK. It is absent from rivers north of the Great Glen, and the River Spey is virtually at the northern limit for this species. Recent surveys show that sea lamprey larvae are widely distributed throughout the middle and lower reaches of the river, where the particularly fast-flowing waters of the River Spey provide ideal spawning conditions for this species. In addition, as an unpolluted and relatively little modified system, the River Spey matches the other key habitat requirements of the sea lamprey in terms of good water quality, clean gravels and marginal silts and an unhindered migration route to the sea.
The River Teith in eastern Scotland represents part of the east coast range of the sea lamprey Petromyzon marinus in the UK. The River Teith is the most significant tributary of the River Forth and young sea lampreys have been recorded throughout the lower reaches of the main river. The conservation importance of the River Teith is increased by the fact that, unlike many British rivers, it supports populations of all three lamprey species.
River Usk/ Afon Wysg
East Wales, West Wales and The Valleys
The Usk is a medium-sized catchment in south Wales, important for its population of sea lamprey Petromyzon marinus. Survey of juveniles and observation of spawning adults indicates that this species is mainly restricted to the lower reaches of the catchment. The site supports a range of Annex II fish species.
River Wye/ Afon Gwy
East Wales, Gloucestershire, Wiltshire and Bristol/Bath area, Herefordshire, Worcestershire and Warwickshire, West Wales and The Valleys
The Wye is an extensive river system crossing the border between England and Wales and the sea lamprey Petromyzon marinus population is found in the main stem below Llyswen. The site provides exceptionally good quality habitat for sea lamprey and supports a healthy population.
Severn Estuary/ Môr Hafren
Dorset and Somerset, East Wales, Extra-Regio, Gloucestershire, Wiltshire and Bristol/Bath area
Species occurrence description not yet available.
Cumbria, Extra-Regio, South Western Scotland
The Solway Firth provides migratory passage for sea lamprey Petromyzon marinus to and from spawning and nursery grounds in a number of rivers, including the Eden which is designated as a cSAC for the species.
SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection
- Afon Teifi/ River Teifi West Wales and The Valleys
- Afon Tywi/ River Tywi West Wales and The Valleys
- Afonydd Cleddau/ Cleddau Rivers West Wales and The Valleys
- Cardigan Bay/ Bae Ceredigion Extra-Regio, West Wales and The Valleys
- Carmarthen Bay and Estuaries/ Bae Caerfyrddin ac Aberoedd East Wales, Extra-Regio, West Wales and The Valleys
- Dee Estuary/ Aber Dyfrdwy Cheshire, East Wales, Extra-Regio, Merseyside, West Wales and The Valleys
- Humber Estuary East Yorkshire and Northern Lincolnshire, Extra-Regio, Lincolnshire
- Pembrokeshire Marine/ Sir Benfro Forol Extra-Regio, West Wales and The Valleys
- River Axe Devon
- River Dee and Bala Lake/ Afon Dyfrdwy a Llyn Tegid Cheshire, East Wales, Shropshire and Staffordshire, West Wales and The Valleys
- River Derwent North Yorkshire
- River Tay Eastern Scotland, Highlands and Islands
- River Tweed Eastern Scotland, Northumberland and Tyne and Wear
- Tweed Estuary Northumberland and Tyne and Wear
Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access.