Rare Migratory Fish of the Firth of Forth

By Jo Girvan

Here at the RFFT, we are very focussed on monitoring and conserving migratory fish species such as Atlantic salmon, sea trout and sea and river lamprey. These species feed at sea, taking advantage of abundant resources and then move up into rivers to spawn at different times of the year – a migratory structure known as anadromy. But there are also a few less well known species that spend much of their time in the Firth of Forth, and move into rivers at spawning time.

Photo from Galloway Fisheries Trust

The sparling (or smelt) for example once formed an important fishery in the Firth of Forth. These fish are a relative of trout and salmon, and share the characteristic adipose fin between the dorsal and tail fins. They live in estuarine and coastal areas, but when it is time to spawn, they move into the mouths of rivers en masse and spawn in one huge event near the tidal limits in the river. In a document from the 19th century, Parnell describes how every available surface on the banks of the River Forth at Stirling would be plastered with their eggs. Until the 1950s, between 10 and 15 tonnes of sparling were fished from the Firth of Forth each year, but unfortunately, the population underwent a crash in the 1960s and has become quite rare. This decline was likely caused by water pollution and enrichment combined with overfishing and habitat destruction. Longannet may well have caused massive mortality by entraining sparling on its screens. Now it has been decommissioned, we may see a resurgence in this estuarine species.

Twaite and allis shad (known as the bony horseman and the alewife respectively) are also present in the Firth of Forth. They are a relative of the herring, and like sparling, they move into freshwater to spawn. They are known from the Solway Firth over on the west coast as well, but it is not known whereabouts in Scotland their breeding sites are. There has not been a commercial fishery for shad in the Forth, although the alewife apparently makes good eating, and so less is known about the welfare of these species over the last century. They are considered to be rare nowadays and are protected under the Habitats Directive and the Berne Convention. The twaite shad pictured was caught last summer off Newhaven pier, much to the surprise of the angler who was going for mackeral. 

Until around 200 years ago, the European sea sturgeon was often found in large British rivers such as the Ouse and Thames. It was also common in Scottish rivers and estuaries including the Firth of Forth, often found as a by-catch in salmon nets. Sturgeon are very long lived and can grow to 3m in length. They are very distinctive due to their bony appearance. They spawn in large rivers, however, it has never been confirmed that sturgeon ever actually spawned in British waters, or if they have simply been vagrants travelling from European rivers. They are critically endangered today, and the nearest known spawning population is in the Gironde River in Southwest France where a conservation and artificial breeding project is under way.

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