Haddock vs Whiting
How to tell them apart, and what follows from getting it right.
Why they get confused
Two slender, silvery gadoids with three dorsal fins, each carrying a dark mark near the pectoral fin, taken over the same ground in the North Atlantic. The mark is what confuses people, because both fish have one; where it sits is the difference.
Haddock
Melanogrammus aeglefinus — Gadidae
Photo: Vsevolod Rudyi, via Wikimedia Commons, CC BY 4.0. Resized and converted to WebP for the web; not otherwise altered.
Whiting
Merlangius merlangus — Gadidae
Photo: rmjb, via iNaturalist, CC BY. Resized and converted to WebP for the web; not otherwise altered.
The differences
Each difference is marked with how far it can be trusted on its own. A single diagnostic character settles the identification; suggestive ones only narrow it.
| Character | Haddock | Whiting | Reliability |
|---|---|---|---|
| The dark mark by the pectoral finIdentification | A smudged blotch ABOVE and behind the pectoral fin, on the shoulder: the 'thumbprint'. | A small, consistent dark spot AT THE BASE of the pectoral fin, where the fin joins the body. | Diagnostic on its own |
| Chin barbelIdentification | Present, though small and much less prominent than a cod's. | Absent in adults; very young whiting can carry a tiny one. | Diagnostic on its own |
| Mouth and snoutIdentification | A small mouth set beneath a pointed snout, for picking food off the bottom. | The upper jaw projects beyond the lower, giving a slightly pointed, overhanging snout. | Supporting — use with others |
| SizeSize | Typically 0.5–1.5 kg; 2.5–4 kg is a large fish. | Typically 200–500 g; 0.8–1.5 kg is a large fish. | Supporting — use with others |
| ColourIdentification | Silvery-grey with a purplish sheen over the back in fresh fish, and a black lateral line. | A sandy or bluish back over silvery flanks. | Suggestive only — varies |
Why it matters
Minimum sizes and catch rules are set per species, so the name matters before anything is kept. Both suffer from being brought up from depth: haddock taken deep cannot be released successfully, and whiting are often deep-hooked because they take baits aggressively, so a disgorger and appropriately sized hooks help with both.
The full species pages
This page compares two species. Each of them has a full page covering biology, behaviour, handling and the evidence behind all of it.
More about haddock
Where it lives, how it is caught, and what else it is confused with.
Similar and related fish
- Atlantic codGadoids sharing water and traces. Haddock have a black lateral line and a dark thumbprint; cod have a pale lateral line. They also feed differently, which decides the bait.
- WhitingSlender North Atlantic gadoids, each with a dark mark by the pectoral fin — above it on a haddock, at its base on a whiting.
How it is caught
- LedgeringA bottom feeder with a small inferior mouth, so small baits presented hard on the bottom outfish larger ones held above it — which is the opposite of what works for cod on the same ground.
Why the 3 connections on this page are here, and the sources
Similar and related fish
Backed by research — 2 connections
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Atlantic cod
An identification and feeding comparison naming both binomials.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: That Melanogrammus aeglefinus and Gadus morhua are both Gadidae of the North Atlantic continental shelf with overlapping distributions.States this directlyPassage read and verified
- The Fishes of the British Isles and North-West Europe — Macmillan, 1969 (Reference work)Relied on for: The morphological separation of haddock from cod by lateral line colour and the shoulder blotch, and their differing feeding habits.States this directlyCitation checked — the work exists and is described correctly
Whiting
An identification comparison naming both binomials: Melanogrammus aeglefinus and Merlangius merlangus.
- FishBase: a global information system on fishes — relied on for: Morphological and distributional data for Melanogrammus aeglefinus and for Merlangius merlangus.
- The IUCN Red List of Threatened Species — International Union for Conservation of Nature (Conservation authority)Relied on for: Separate assessments treating Melanogrammus aeglefinus and Merlangius merlangus as distinct species.States this directlyCitation checked — the work exists and is described correctly
How it is caught
What experienced anglers do — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Ledgering
A practitioner claim following from the species' verified feeding morphology.
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Practitioner treatment of bait size and presentation for haddock in relation to cod on the same ground.Citation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practitioner guidance that haddock take small baits fished hard on the bottom.Citation checked — the work exists and is described correctly
Reviewed 2026-10-19. FishingHQ does not state what any rule is or where any rule applies. Where this page says the two species are managed differently, that is a reason to check the authority for the water you are on — not a statement of what it requires.