How to Identify UK Fish

By Alex Clayton · Updated 23 October 2026

You have a silver fish in the landing net and three possible names for it. This fish identification UK guide works through one order of checks: body shape and mouth, then fins, then scales and eye, then the look-alikes within its group.

This guide covers freshwater fish (coarse, carp, predator and game) and the common sea species, because most ID pages only do one or the other.

Getting the name right also matters legally. In England, eels, shad and early-season salmon have to go straight back, and Step 9 covers the rest. First, though, look after the fish while you work it out.

Step 1: Keep the Fish Safe While You Check It

Photos let you finish the ID once the fish is back in the water.

Leave the fish in the landing net in the margin, or lay it on a wet unhooking mat. Wet your hands before you touch it.
Take a side-on photo with the fins spread, then a close-up of the mouth and eye.
For bream and silver fish, add a shot of the flank between the dorsal fin and the lateral line, so you can count scale rows later (Step 4).

On the coast, the greater weever buries itself in sand and has venomous spines on its gill cover and first dorsal fin. Handle unfamiliar fish from sandy beaches with care, and get medical advice after a sting.

More on unhooking is in safe catch and release. If you are unsure what you have, photograph it and get it back first.

Step 2: Sort It by Body Shape and Mouth

The mouth tells you more than colour does, because it shows how and where a fish feeds. Combine it with body shape and most UK fish drop into a group straight away.

What you see	Likely group	Go to
Long torpedo body, flat-topped snout, wide mouth full of sharp teeth	Pike	Step 7
Spiny dorsal fin, often a barred flank	Perch, zander or ruffe	Step 7
Slender or medium silver fish, small mouth, no barbels	Roach, rudd, dace or chub	Step 5
Tall, deep, flat-sided body	Bream or silver bream	Step 6
Barbels at the mouth, or an underslung mouth	Carp, barbel, gudgeon or tench	Step 6
Trout-shaped and spotted	Brown trout or salmon	Step 7
Flat, both eyes on one side	Flatfish	Step 8
Snake-like, smooth, no obvious scales	Eel (a lamprey has a sucker mouth and no pectoral fins)	Step 9

Then look at the mouth itself:

Upturned: the rudd, with its protruding lower lip.
Underslung: the barbel. A bream’s is slightly undershot and extends forward.
Barbels: four on a barbel, two on a gudgeon, a tiny one each side on a tench. Common carp have them too.
Teeth: numerous sharp teeth on a pike; two long canines on a zander.

To browse by group instead, use the full UK species directory. Skip this sort if you already know you have a flatfish.

Step 3: Count the Dorsal Fins and Check Their Colour

A haddock has three dorsal fins, a mackerel two plus finlets, and a ruffe one. For freshwater fish identification in the UK, the fins are your second check after shape.

One dorsal or two: a perch has a spiny first dorsal and a separate, softer second one. A zander’s is also split, with 13 to 20 spines in the first part. A ruffe’s is one continuous fin, spiny at the front and soft at the rear.
Dorsal position: a rudd’s dorsal sits further back than a roach’s.
Long dorsal: a common carp’s has a serrated first spine. A crucian’s is convex with a weak leading ray, but sources disagree on that edge, so back it up with other cues.
Fin colour: roach fins are red to dark reddish-brown, chub fins reddish and rounded, dace fins duller and brownish. Perch have red pelvic, anal and tail fins. Bream fins are dark brown to grey-black.
Anal fin edge: a dace’s is concave (inward-curving).

Quick comparison: dull fins and a concave anal fin mean dace; redder, rounded fins on a bigger fish, chub.

Step 4: Read the Scales, Lateral Line and Eye

Zoom in on your Step 1 photo and you can count scale rows without touching the fish again.

Scales. On bream, count the rows from the first dorsal ray down to the lateral line (Step 6 explains what the count means). Tench have very small, deep-set scales and a slimy feel. Carp come in four scale patterns: fully scaled common carp, mirror carp with large scattered scales, linear carp with a single row along the lateral line, and leather carp, which are virtually unscaled.

Eye. A roach usually shows a red spot in the iris above and beside the pupil, though it can be pale in some waters. Dace have a yellowish iris, tench a small red-orange eye and zander large, glassy eyes.

Lateral line. On sea fish, this line along the flank is often the giveaway (Step 8).

Still undecided? You probably have one of the pairs below, or a hybrid.

Step 5: Separate Roach, Rudd, Dace and Chub

A silver fish from a mixed river or canal could be any of four species, and colour is the cue that fails most often, because fin and eye colour can be pale in some waters. Identifying roach, rudd, dace and chub works best when you look for the one decisive feature each carries.

Species	Body	Mouth	Fins	Eye	Size guide	Decisive check
Roach	Silvery, deeper than chub and dace	Not upturned	Red to dark reddish-brown	Red spot in the iris	10 to 40 cm	Red eye spot; dorsal further forward than a rudd’s
Rudd	More yellow or golden	Upturned, protruding lower lip	Dorsal set further back	Not decisive	Not decisive	Lower lip and dorsal position
Dace	Slender, silvery	Not decisive	Duller, brownish; concave anal fin	Yellowish iris	Roughly 15 to 25 cm	Concave anal fin edge
Chub	Slender, greenish-silver	Not decisive	Reddish and rounded	Not decisive	Around 30 to 40 cm	Bigger than dace, with redder fins

Still stuck between roach and rudd? Count the scales between the tip of the pelvic fin and the start of the anal fin. A roach typically has 4 to 5 there, a rudd 1 to 2. The roach vs rudd guide goes deeper.

Some fish will match none of these rows. Roach x rudd and roach x bream hybrids exist and fit no single description, so a fish with mixed features may be a cross rather than a misread. See hybrid coarse fish, and the coarse fish species hub for the full list.

If the lower lip juts out, it is a rudd: start there.

Step 6: Tell Bream, Silver Bream, Carp, Barbel and Tench Apart

A young common bream can be as silver as a silver bream and reach a similar size, so colour tells you almost nothing. For deep-bodied and bottom-feeding fish, two checks do the work: scale rows and barbels.

Common bream or silver bream?

Count the scale rows from the first dorsal ray down to the lateral line. A silver bream has around 10 or fewer; a common bream has well over 10. Sources give slightly different thresholds, so treat this as the most reliable field check rather than an exact number.

Supporting cues help. A common bream is tall and flat-sided, bronze when adult, with dark fins and a deeply notched tail. Adult silver bream may show a reddish tint to the fins and a big eye. When I’m feeder fishing for bream, a flank photo and a scale count is the quickest way I’ve found to settle it.

Barbels decide the rest

Fish	Barbels	Other cue
Common carp	Present	Long dorsal with a serrated first spine
Crucian carp	None	Convex dorsal, well-rounded snout; juveniles have a dark spot at the tail base
Barbel	Four	Underslung mouth, slender body, often reddish-orange fins
Gudgeon	Two	Small (7 to 15 cm), dark blotches along the flank
Tench	A tiny one each side	Olive-green, tiny scales, slimy, red-orange eye, rounded fins

Goldfish and crucian hybrids are harder to call from these cues alone, so check the hybrid coarse fish guide rather than forcing a name. For every variety, browse the carp species section.

Quick check: no barbels means it is not a common carp.

Step 7: Tell the Predators and Game Fish Apart

A small zander has a split, spiny dorsal like a perch and long canines like a pike, so check both its fins and its mouth.

Fish	Dorsal fin	Teeth and mouth	Markings
Pike	Not the key cue	Flat-topped snout, wide mouth, many sharp teeth	Olive-green, pale cream spots or bars
Zander	Split; 13 to 20 spines in the first part	Two long canines, large glassy eyes	Dark bars, rows of black spots on dorsal and tail fins
Perch	Spiny first dorsal	No long canines	Greenish, 5 to 8 dark bars, red lower fins, humped back on big fish
Ruffe	One continuous fin, spiny front, soft rear	Slightly downturned	Olive to golden brown, about 10 to 20 cm

The ruffe is native; the zander was introduced at Woburn Abbey in 1878.

On Windermere, the dorsal fin is the first thing I check on a small barred fish from the drop-shot. Two separate dorsals and red lower fins mean perch.

Game fish. A brown trout is golden-brown, with dark and red spots that have pale borders, and a square-ended tail. An Atlantic salmon is silvery, with black spots mainly above the lateral line, a forked and usually unspotted tail, and a hooked jaw (kype) on breeding males. Sea trout have their own guide, sea trout vs salmon. The salmon rule in Step 9 makes this pair worth getting right.

Two dorsals and bars: perch or zander. Look for the canines, then see the predator species hub.

Step 8: Identify Common UK Sea Fish

Run your eye along the lateral line first. On pollack, coalfish, haddock and dab it is the quickest single tell, so for sea fish identification UK anglers can treat it the way they treat the fins in freshwater.

Pollack or coalfish? Pollack have a strong underbite, a crooked lateral line and a brown back. Coalfish have a clean, strongly defined silvery lateral line, a greenish-black back and a white belly.

Cod or haddock? Haddock have a black lateral line, a dark thumbprint blotch above the pectoral fin, a small chin barbel, and three dorsal and two anal fins. Cod are brown or green with spots, silvery below, with a clear pale stripe along the lateral line.

Mackerel. Steel-blue with wavy black lines, two dorsal fins and a row of finlets near the tail.

Flatfish. All three common flatfish have both eyes on one side, so look at the skin, the spots and the lateral line:

Fish	Skin and colour	Spots	Other
Plaice	Smooth	Orange	Bony ridge behind the eyes; right-eyed
Flounder	Rough tubercles along the lateral line and fin bases	Reddish, irregular	Eyes on the left in about 30 per cent; enters estuaries and rivers
Dab	Pale brown	No orange spots	Lateral line curves in a semicircle above the pectoral fin; usually 25 to 40 cm

Handle anything weever-like with care (Step 1). Sharks and skates carry their own rules (Step 9), and the sea fish species hub covers the rest. Smooth with orange spots is a plaice; rough along the lateral line is a flounder.

Step 9: Check the Rules Before You Keep or Move It

The species decides whether you can keep a fish, so a wrong name can mean breaking a byelaw. These are England rules from the national rod fishing byelaws. Elsewhere, check with the Scottish Government, Natural Resources Wales or DAERA (see rules in Scotland, Wales and Northern Ireland).

Species or situation	Rule (England)
Any fish you cannot keep	Return it to the water unharmed; release foul-hooked fish immediately
Eels and shad	Return to the same water unharmed (the eel is Critically Endangered on the IUCN Red List)
Salmon	Illegal to catch and remove before 16 June; release immediately. Selling salmon or sea trout is illegal (salmon fishing rules)
Keeping coarse fish on rivers	Daily limits apply; local byelaws differ (size and take limits)
Moving fish	Written Environment Agency agreement needed; use live bait only in the water it came from

In England and Wales, Chinese (Amur) sleeper, pumpkinseed, striped eel catfish and topmouth gudgeon are listed invasive non-native species. Report them if found in the wild; releasing them is banned under the Wildlife and Countryside Act 1981 (invasive species).

At sea, you may not land tope caught from a boat, dead or alive. Angel shark and white skate must be returned and are protected within 12 nautical miles of the English and Welsh coast. See also sharks, sea fish minimum sizes, the rod licence and freshwater rules.

If you can’t name it, put it back.

Frequently asked questions

What fish have I caught?

Check body shape and mouth, then the fins, then the scales and eye (Steps 2 to 4). That narrows most UK fish to a group, then a species. If you are still unsure, photograph it, return it and compare against the species directory.

How do you tell a roach from a rudd?

A rudd has an upturned mouth with a protruding lower lip and a dorsal fin set further back. A roach usually has a red spot in the eye. See Step 5 for the scale count that settles it.

Do I have to know the species to follow the fishing rules?

Yes. In England, eels, shad, salmon before 16 June and listed non-native species carry their own rules, and anything you cannot keep goes back unharmed. Elsewhere in the UK, check with the relevant authority (Step 9).

Are there good fish identification books for the UK?

Yes. Countryfile lists David Weaver's Coarse Fish Identification United Kingdom (one fish per page) and Greenhalgh and Carter's Freshwater Fish of Britain and Europe (more than 160 species, Europe-wide).