UK Flatfish Species

By Alex Clayton · Updated 24 October 2026

The types of flatfish UK sea anglers catch most often are plaice, flounder, dab, sole, turbot and brill. The quickest way to narrow one down is the eye side: eyes on the left points to turbot or brill, eyes on the right points to plaice, flounder, dab or sole.

On the shingle, most UK flatfish species look like the same brown oval. Four quick checks separate them. Below you will find how to identify each one, where each lives, and what size you can keep, which depends on where you fish.

Left-Eyed or Right-Eyed: The Two Flatfish Families Anglers Meet

Flatfish are not born flat. The young fish swim upright like any other fish, then one eye migrates across the head and the fish settles on the seabed on one side, with both eyes on the side that faces up. That side is your first identification check.

The right-eyed family, Pleuronectidae, includes plaice, flounder and dab. Sole also have their eyes on the right. The left-eyed family, Scophthalmidae, includes turbot and brill.

To check, lay the fish dark side up with its belly towards you. If the head points to your right, it is right-eyed. If it points left, it is left-eyed.

Flounder break the rule. They are usually right-eyed, but roughly 30% are left-eyed, so a left-eyed fish with a prickly lateral line is still probably a flounder.

If the eyes are on the left and the body is broad, go straight to the turbot and brill guide.

The Main Types of Flatfish in UK Waters

Six species cover most of the flatfish you will meet around the UK coast. This table puts them side by side.

Species	Eyes	Key ID feature	Typical size	Where you find it
Plaice	Right	Smooth skin, bright orange spots, bony ridge behind the eyes	See the plaice guide	Sand and mixed seabed
Flounder	Usually right (about 30% left)	Rough prickles along the lateral line and fin bases; lateral line almost straight	See the flounder guide	Estuaries and tidal rivers; copes with low salinity
Dab	Right	Sharp arch in the lateral line above the pectoral fin; rough-edged scales; no orange spots	Usually under 20 cm, up to about 40 cm	Sandy seabed
Sole	Right	Small, close-set eyes; grey-brown body	Up to about 70 cm	Sandy or muddy bottoms, feeding mainly at night
Turbot	Left	Broad, diamond-shaped body	Up to about 1 m	Sand and mixed ground
Brill	Left	Slimmer oval body; frilly front edge to the dorsal fin	Up to about 75 cm	Sand and mixed ground

Plaice carry the most obvious markings of the six, and the plaice guide covers them in full. Flounder are the estuary specialist, covered in the flounder fishing guide. The dab guide shows that lateral line arch in detail.

Sole feed after dark and have their own sole guide. Turbot and brill get mixed up so often that they share one page, the turbot and brill guide.

Other flatfish turn up now and then. Lemon sole is one, and it appears in the Channel size rules below.

Flatfish Identification: Which One Did You Catch?

You have a brown flatfish on the shingle with a few orange-ish marks, and it could be a plaice, a flounder or a dab. Work through these four checks in order.

Eyes. Eyes on the left means turbot or brill. Eyes on the right means plaice, flounder, dab or sole.
Feel the lateral line. Run a wet finger along the lateral line and the bases of the fins. Rough prickles mean flounder.
Spots and lateral line shape. Smooth skin, bright orange spots and a bony ridge behind the eyes mean plaice. A sharp arch in the lateral line over the pectoral fin, rough-edged scales and no orange spots mean dab.
Eyes and body shape. Small, close-set eyes on a grey-brown body mean sole. A broad diamond means turbot. A slimmer fish with a frilly front edge to the dorsal fin means brill.

When the checks disagree

Flounder can be left-eyed, so trust the prickles over the eye side. Turbot and brill are known to hybridise, so the odd left-eyed fish shows features of both parents. If a fish fits nothing cleanly, photograph both sides before you return it.

Keep handling brief, use wet hands, and put undersized fish back quickly.

Plaice and dab cause the most second-guessing. The dab identification guide has close-up detail on the lateral line arch that settles it.

Where to Fish for Flatfish From the UK Shore and Boat

Flatfish fishing in the UK is less about finding rocks and structure and more about reading the seabed. Flatfish lie on the bottom and feed there, so the type of ground decides which species you are likely to meet.

Flounder tolerate low salinity and run into estuaries and tidal rivers, so start at estuary marks (flounder guide).
Sole feed mainly at night over sandy or muddy bottoms, so fish for them after dark (sole fishing guide).
Plaice and dab are fish of sand and mixed seabed.
Turbot and brill also live over sand and mixed ground, but they tend to be more of a boat target than a shore one.

The usual starting point is the same for all of them: a baited rig fished hard on the seabed, with small hooks and worm baits. Rigs, hook sizes and baits differ by species, so check the species guide before you tackle up.

Best for: beginners. An estuary flounder is a sensible first flatfish, because estuary marks can be fished from the bank. Skip if: you fish from the shore only and want turbot. They are rarely a sensible first target until you go out on a boat.

For other shore and boat species, go back to the UK sea fish guide.

Flatfish Minimum Sizes: What You Can Keep in UK Waters

Search for a flounder size limit and you will often see 25 cm quoted as if it applies everywhere. In the retained UK rules checked for this guide, flounder and dab have no national minimum size. Their limits come from local Inshore Fisheries and Conservation Authority (IFCA) byelaws.

Only plaice and sole have one statutory minimum size across the North Sea and western waters. Turbot, brill and lemon sole have statutory sizes only in the eastern and central English Channel (ICES divisions 7d and 7e), inserted on 16 December 2024.

Species	Statutory minimum	Where it applies	Cornwall IFCA example
Plaice	27 cm	North Sea and western waters	27 cm
Sole	24 cm	North Sea and western waters	24 cm
Turbot	30 cm	Eastern and central Channel (7d, 7e) only	30 cm
Brill	30 cm	Eastern and central Channel (7d, 7e) only	30 cm
Lemon sole	25 cm	Eastern and central Channel (7d, 7e) only	25 cm
Flounder	None	Set by local IFCA byelaw	25 cm
Dab	None	Set by local IFCA byelaw	15 cm

Statutory sizes come from retained Regulation (EU) 2019/1241, Annex V, Annex VI and Annex VII. Cornwall figures come from Cornwall IFCA’s information sheet (September 2025). Its legacy byelaw does not apply in some small areas.

So 25 cm for flounder is Cornwall IFCA’s figure, not a national one. Eastern IFCA lists only sole (24 cm) and plaice (27 cm), and states that fish below these sizes must be returned. Devon and Severn IFCA publishes no flatfish sizes online, so contact it directly at office@devonandsevernifca.gov.uk or on 01803 854648.

Wales, Scotland and Northern Ireland sit outside the IFCA system, so anglers there should check with their own fisheries authority.

Lay the fish flat and measure from the tip of the snout to the end of the tail before deciding. Before every trip, look up your district IFCA’s minimum size page. Sizes checked October 2026.

Frequently asked questions

What is the difference between a plaice and a flounder?

A plaice has smooth skin, bright orange spots and a bony ridge behind the eyes. A flounder feels rough, with prickles along the lateral line and fin bases, and about 30% are left-eyed. The flounder guide covers it in more detail.

Are turbot left or right eyed?

Turbot are left-eyed, and so are brill. Turbot have a broad, diamond-shaped body. Brill are slimmer, with a frilly front edge to the dorsal fin. The turbot and brill guide covers both.

What size flounder can I keep in the UK?

There is no single national minimum size for flounder in the retained rules checked for this guide. It depends on your local IFCA byelaw. Cornwall IFCA sets 25 cm, for example. Check your district's minimum size page before you fish.

Can you catch flatfish from the shore?

Yes. Flounder are a shore fish of estuaries and tidal rivers, plaice and dab live over sand and mixed ground, and sole feed mainly after dark over sand or mud. Turbot and brill tend to be boat targets.