Allis Shad
Allis shad are a large, herring-family fish that spend most of their lives at sea before running into rivers to spawn each spring. In the UK they are extremely rare and fully protected by law — it is illegal to target, retain or even handle one.
Anglers are most likely to encounter them accidentally in the Severn, Wye, Tamar or Solway estuaries while fishing for bass, mullet or sea trout.
Scientific Name: Alosa alosa
Also known as May fish
- Silvery, laterally flattened body with large scales and a deeply forked tail — looks like an oversized herring, typically 30–50 cm, occasionally reaching 60 cm or more.
- Key ID mark: a single prominent dark spot just behind the gill cover; occasionally one to six smaller spots in a row behind it — twaite shad usually show a row of 3–10 spots.
- Lower jaw fits into a distinct notch in the upper jaw; a thin fatty membrane partially covers the eye front and rear — useful close-up ID features.
- British record stands at 4 lb 12 oz. Allis shad run larger on average than twaite shad, which rarely exceed 40 cm.
What to know
Habitat Distribution
- Native to UK coastal and estuarine waters; spends adult life at sea then migrates into rivers to spawn — classed as anadromous, like salmon.
- Extremely rare in the UK. The Severn and its tributaries (Wye, Usk) hold the most significant known populations; the River Tamar and Solway Estuary are also recorded sites.
- Spawns over clean, shallow gravel runs adjacent to deeper pools in rivers — well-oxygenated water is essential for egg survival. Weirs and dams have cut off most historical spawning habitat.
- At sea, found in coastal and offshore waters down to around 150 m; enters estuaries and tidal reaches during the spring spawning run.
Key Locations
- River Severn and its tributaries (Wye, Usk) — the most significant remaining UK population, with ongoing habitat restoration work to reopen historical spawning grounds above Diglis Weir.
- River Tamar, Devon/Cornwall — a known spawning population recorded by MarLIN and conservation surveys.
- Solway Estuary, Scotland — shad are most commonly associated with this area in Scottish waters, though spawning sites remain poorly documented.
- Estuaries of the Humber and Towy — listed as areas where anglers may encounter shad as accidental bycatch during spring bass and mullet fishing.
Specific Spots
- During the spawning run, fish concentrate below weirs and other obstacles — these are the natural holding points where migration stalls.
- Shallow, gravelly runs next to deep pools are the preferred spawning areas; adults gather here at night with audible surface splashing.
- Tidal reaches and estuary mouths are where accidental bycatch most often occurs — anglers targeting bass or mullet near river mouths in spring are most at risk of an encounter.
Allis Shad FAQ
Answers from onWater's species guide.
When is the best time to fish for Allis Shad?
Spring (April–June), the only time allis shad are present in UK rivers and estuaries, during their spawning run. Outside this window they are at sea and effectively inaccessible. Peak spawning activity occurs at night during the height of the run, when fish are most visible and most likely to be encountered as bycatch.
How do you catch Allis Shad?
Targeting allis shad is illegal in the UK. Anglers fishing estuaries and tidal rivers for bass, mullet or sea trout in spring should be aware of the risk of accidental bycatch, use barbless hooks, and be prepared to release any shad immediately and without handling.
What do Allis Shad eat?
At sea, allis shad feed on marine crustaceans, zooplankton filtered through their dense gill rakers, and small fish. Once they enter freshwater to spawn, digestion effectively shuts down, but fish will still react to surface insects such as mayflies and terrestrial invertebrates out of instinct rather than hunger.
Where do Allis Shad live?
Native to UK coastal and estuarine waters; spends adult life at sea then migrates into rivers to spawn, classed as anadromous, like salmon. Extremely rare in the UK. The Severn and its tributaries (Wye, Usk) hold the most significant known populations; the River Tamar and Solway Estuary are also recorded sites.
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