Allis shad (Alosa alosa) and twaite shad (Alosa fallax)

Lampern (Lampetra fluviatilis) and sea lamprey (Petromyzon marinus)

Sturgeon (Acipenser sturio

Candidate SACs: Afon Tywi, River Wye, River Usk

Allis shad (Alosa alosa) and Twaite shad (Alosa fallax) migrate up rivers to spawn, the adults returning immediately and juveniles at a later stage. The population of the Allis shad in the UK has declined since the mid-nineteenth century to the point where it has a sporadic distribution around the coast with no known spawning grounds/rivers. The Twaite shad has also declined and spawning populations are thought to be restricted to the Severn, Usk, Wye and Twyi and possibly rivers feeding the Solway Firth.

Static gear fisheries operate in the locations frequented by both species and there are reports of catches in drift nets and salmon nets as well as occasional catches by anglers⁶¹. The main reasons for the decline of these species are considered to be poor water quality and obstructions in rivers which prevent migration for spawning rather than any impact associated with fisheries⁶¹.

Candidate SACs: River Wye, River Usk

The lampern (Lampetra fluviatilis) is widespread in the UK with substantial populations in some rivers and streams although not present in others where they used to be common. The main populations are probably those which migrate into the Severn estuary from the Bristol Channel and adjacent offshore waters. The sea lamprey (Petromyzon marinus) is uncommon in the UK and although found around the coast, the main population centres are concentrated on the Bristol Channel. Both species migrate up rivers to spawn and spend the larval stage buried in the muddy substrates in freshwater. Once metamorphosis takes place the adults migrate to the sea where they live as a parasite on various species of fish.

The sea lamprey has been commercially fished throughout its European range but this is now generally limited to some small local fisheries. The main reasons for its decline and that of the lampern are considered to be poor water quality, and obstructions in rivers which prevent migration for spawning rather than any impact associated with fisheries⁶¹.

Possible SACs: None

The west European (Atlantic) population of the common sturgeon (Acipenser sturio) is known to have had a range extending from the Atlantic coast of France to the Severn Estuary and Pembrokeshire in western Britain, and up to the Firth of Forth on the Scottish east coast and the Limfjord on the west coast of Denmark in the North Sea. There are now few catches in these waters and the only location where a spawning stock is known to remain in this range is the Gironde basin in France. The adults migrate into estuarine and brackish waters to spawn and juveniles move between estuaries and the sea. The causes of its decline in Europe have been a directed fishery, pollution of the lower reaches of rivers, damage to spawning grounds and man-made obstacles restricting migration. There have also been reports of accidental catches in trawls and nets at sea and in estuaries when fishing other species, which add another pressure on stocks⁶⁰.

The sturgeon is only occasionally reported in UK waters and unlikely to be found moving into estuaries to spawn. Reintroduction programmes are being considered in France and if sturgeon do become more common in UK waters as a result, the reduction of physical obstacles for migrating fish, safeguarding spawning grounds in rivers and estuaries, and care over any incidental catch will be important factors in assisting any recovery^60,61.

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