Haddock Fishing: The Predator Named After the Line, Not the Dot
Every article in this series answers the same question: how does the angler outwit the predator? With which bait, at what depth, at what time. With the haddock the answer starts with a misunderstanding. Everyone knows the fish by the black blotch above its pectoral fin — the “thumbprint” the legends are built on. But the man who gave it its scientific name in 1758 did not mean the blotch. He meant the line. Hence this article’s pole: the predator named after the line, not the dot. The fish meant here is the haddock, *Melanogrammus aeglefinus*, at home from the Arctic seas to the English Channel.
The black line and the borrowed name
The origins of the scientific names are recorded by The ETYFish Project, an etymological register of fish names. There the genus Melanogrammus is built from Greek *mélanos*, “black”, and *grammḗ*, “line or stroke of the pen” — and according to ETYFish it refers explicitly to the fish’s black lateral line: “referring to its black lateral line”. Not to the blotch. In the haddock the lateral line runs as a dark, uninterrupted stroke to the end of the body, and that is what the namer saw. The most famous dot in the North Sea is not in the name.
The species name is even better. aeglefinus is, according to ETYFish, “apparently a Latinization of ‘Eglefin,’ its vernacular name in England according to Pierre Belon, *De aquatilibus* (1553)” — apparently a Latinisation of a common name that the French naturalist Pierre Belon wrote down in the sixteenth century. The direction is remarkable: usually the vernaculars borrow from Latin, here Latin borrowed from the vernacular. ⚠️ Two caveats belong with it. ETYFish says “apparently”, with reservation. And Belon records “Eglefin” as a name “in England”, although the word looks French and is *églefin* in French to this day — none of the sources read here resolves that contradiction, and this article does not resolve it either.
The common names themselves fall into four camps. The GBIF vernacular list for *Melanogrammus aeglefinus* (key 2415822, 169 entries across 42 languages) holds the eglefin camp, Belon’s trail: French “Églefin” and “Aiglefin”, Spanish “Eglefino”, Catalan “Eglefí”. Next to it the blotch camp, which puts the dot into the name after all: Polish “Plamiak”, Lithuanian “juodadėmė menkė” — the black-spotted cod — and Japanese “モンツキダラ” alongside the usual “コダラ”. Then the northern camp: German “Schellfisch”, Dutch “Schelvis”, Danish “Kuller”, Swedish and Finnish “Kolja”, Norwegian “Hyse” and “Kolje”, Icelandic “Ýsa”, Russian “пикша”, Irish “cadóg”, Welsh “Hadog”. And finally the donkey camp: French “Âne”, “Bourricot” and “Anon”, Italian “Asinello”, Breton “anon”. ⚠️ Why a donkey of all things is given in none of the sources read — this article does not guess. The same goes for “Schellfisch” and “Kuller”: left unexplained because unproven.
💣 And then the naming traps, four of them — and all four mean a different fish that this series has already given its own article. French “Saint-pierre” really does appear in the haddock list, attested three times over (Catalogue of Life, the EUNIS database, the IUCN Red List) — but in French “Saint-Pierre” is the John Dory (*Zeus faber*), the other fish with the thumbprint. Turkish “mezgit” appears there too (Catalogue of Life, WoRMS) — usually “mezgit” is the whiting (*Merlangius merlangus*). Albanian “Troftë deti” appears there (Catalogue of Life) — literally “sea trout”. And Portuguese “Bacalhau” appears there (EUNIS) — that is the cod (*Gadus morhua*). For Greek and Arabic the list carries no name at all across all 42 languages. That is why this article carries the scientific name in the title in those languages, rather than naming a different fish. One footnote for honesty: the same list also holds dishes instead of fish names — “Schellfisch Suppe”, “Fiskekaka”, “Pâté de poisson”. Anyone reading such lists reads those too.
The blotch, the legend, and what the scientific sources do not say
The blotch has a story of its own, told in northern Europe for centuries: that it is a thumbprint — sometimes the Apostle Peter’s, who took the coin from the fish’s mouth, sometimes the devil’s, whose burning grip the fish wriggled out of. Two fish carry the same legend, the haddock and the John Dory, and the French name list above has already mixed the two up. ⚠️ The guardrail matters here: none of the four scientific sources read for this article — ETYFish, GBIF, FishBase, the Institute of Marine Research — explains the blotch that way. It is folklore, not a finding. And ETYFish explicitly says something else: the name comes from the line.
Where exactly the blotch sits is answered differently by the sources. The FishBase species page places it “above the pectoral fin just below the lateral line”. Norway’s Institute of Marine Research (Havforskningsinstituttet) writes: “Hysa er lett kjennelig på den svarte flekken under den fremste ryggfinnen” — easily recognised by the black spot beneath the first dorsal fin. Both describe the same region of the body from two angles, but they say it differently, and this article does not smooth that over. What both share: the blotch sits forward, above the pectoral fin, below the start of the first dorsal — and it is the feature by which you know the fish.
The remaining basic data, each with its source. FishBase: marine, demersal, 10 to 450 metres, usually 10 to 200 metres; the North Atlantic and adjacent Arctic, from the Mediterranean to southern Greenland, Iceland and the southern Barents Sea eastward to the Kara Sea; up to 112 centimetres and 16.8 kilograms, but commonly only 35 centimetres; maximum reported age 20 years. On its build: a “relatively small mouth”, the lower jaw shorter than the upper, plus a small chin barbel. Adults, FishBase says, hold at 80 to 200 metres over “rock, sand, gravel, or shells” at 4 to 10 °C. The food is “small bottom-living organisms”: crustaceans, molluscs, echinoderms, worms and fishes — sand lance, capelin and herring are among those named. Danger to humans: “harmless”. FishBase lists it as “highly commercial” and at the same time as a gamefish.
⚠️ One date has to be read along with the rest: FishBase gives the haddock the IUCN status “Vulnerable” (criteria A1d+2d) — assessed on 1 August 1996. That assessment is thirty years old. This article therefore does not claim what the IUCN would say today; it says only what FishBase carries, and names the date with it. Anyone who needs the current stock status for their own sea area will find it at the responsible fisheries authority, not here.
Two stocks, two sizes of fish
For the angler the most important number in this article is not a depth or a weight but a distinction. The Institute of Marine Research reports the stocks separately, and they differ greatly in size:
- North-east Arctic (Barents Sea, northern Norway): up to 110 centimetres, 14 kilograms, up to 20 years old. Spawning March to June, with the western edge of the Tromsø Bank named by the institute as the main spawning ground.
- North Sea, Skagerrak and west of Scotland: up to 60 centimetres, 4 kilograms, up to 15 years old. The same fish, barely half the length and less than a third of the weight.
- What that means: a 60-centimetre haddock is an exceptional fish in the North Sea and an average one in the Barents Sea. Expectations belong to the sea area, not to the record figure on the species sheet.
- One fish, two names: in Norwegian it is hyse and kolje — along the south and east coast more often kolje. Anyone reading Norwegian catch reports should search for both words.
What that means on the water
- It holds on the bottom, not in midwater. FishBase gives 80 to 200 metres for adults, over rock, sand, gravel or shell at 4 to 10 °C. Looking for it over deep ground means looking where the sources describe it — none of the sources read proves that any particular angling method catches haddock, and this article promises none.
- The small mouth is the difference. FishBase explicitly describes a “relatively small mouth” and a diet of small bottom-living animals — crustaceans, molluscs, worms. That is a different predator from the one that swallows a whole herring. Take the description seriously and bait size points small, not large.
- The blotch is your feature, not an identification key. Black blotch forward, dark unbroken lateral line, short lower jaw, small chin barbel — that is how FishBase and the Institute of Marine Research describe it. This article is still not an identification key; if you need to know the species for certain, ask the responsible authority or consult a field guide.
- The record figure is not your figure. FishBase gives 112 centimetres, and it gives 35 centimetres as the common size. Between those two numbers lies the whole difference between a headline and a day’s fishing.
- Check the rules yourself. This article deliberately gives no minimum sizes, quotas or closed seasons — haddock is a heavily fished food fish, and the rules differ by country and sea area. The responsible fisheries authority is what counts; this is not legal advice.
- Harmless means harmless. FishBase lists it as “harmless” — no venomous spines like the weever, no teeth like the monkfish. The risk on board is the sea, not the fish.
The haddock is the fish that shows how easily the most conspicuous feature is taken for the most important one. The blotch is the story everybody tells; the line is the one written into the name. Fishing works the same way: what stands out is rarely what decides. StrikeAhead reads conditions and depth and learns from your catches; the app tells you when it is worth it, and StrikeAhead Pathfinder tells you who to head out with on unfamiliar water — curated, personally vetted, with verified catches instead of promo photos.