The May Fish Have Arrived

26th May, 2020

By late May and early June, shoals of Twaite shad (Alosa fallax) can usually be seen congregating in the upper Wye and the middle reaches of the Usk in anticipation of spawning.

And this year, two members of the Foundation’s operations team, brothers Louis Macdonald-Ames and Meyrick Ames, were ready for them, taking some extraordinary underwater and aerial footage of this annual visitor.

The Twaite’s larger relative, the Allis shad (Alosa alosa), is much rarer. Although we receive occasional reports of anglers accidentally catching over-sized shad which could be Allis, it is thought that our two rivers no longer support a viable breeding population.

Members of the herring family, both fish have streamlined bodies covered with distinct, large, circular and bright silver scales. Twaite shad spawn at night on gravels and sands at the tail of deeper pools and their eggs are released into the water column, sinking into the gravels below.

Most of the adult fish die after spawning although UK populations appear to have an unusually high proportion of repeat spawners – up to 25%. After hatching the fry develop and slowly drift downstream. Relatively little is known about the marine stage of their lifecycle, although they are thought to spend their adult life in coastal waters and estuaries before entering river systems.

Twaite shad are found along the western coastline of Europe, from southern Norway to Morocco and along the eastern Mediterranean. Their numbers have, however, declined substantially, probably due to pollution, overfishing and barriers to migration. Allis shad are rare and declining throughout their range on the western coasts of Europe, from southern Norway to Spain, and in the Mediterranean eastwards to northern Italy.

In the UK, spawning stocks of Twaite shad are known to occur in only a few rivers in Wales, including those flowing into the Severn estuary. No spawning stocks are known north of this, although the species is present in rivers flowing into the Solway Firth in south-west Scotland.

Shad have been known to migrate 800km upstream in rivers in continental Europe. However, both species are not particularly adept at traversing obstacles to migration such as dams, weirs or bridge footings. On the Wye they usually reach as far as Builth Wells and a short distance up the Irfon, while on the Usk, Abergavenny bridge footings is usually the furthest upstream they are found.

Both species are listed as Annex II species under the EU Habitats Directive. Although it is illegal to target them, many salmon and trout anglers are given a surprise by a savage take on their fly or spinner at this time of year.

However, shad do not respond well to handling so anglers are urged to release them immediately if hooked accidentally.