Haddock wear a black thumbprint called the Devil's mark
Melanogrammus aeglefinus, the lone species in its genus, carries a dark lateral line and an oval shoulder blotch that earned the Greek name for black letter. North Atlantic fisheries smoke it as Finnan haddie or Arbroath smokie, yet most fish stay under eighty centimetres even though giants have hit ninety-four.
Three dorsal and two anal fins, a small chin barbel, and a wedge snout mark the gadid body. Colour runs dark grey-brown above and silvery below. Record length is 94 centimetres and 11 kilograms; United Kingdom catches usually measure 30 to 70 centimetres, eastern Canadian fish often 38 to 69 centimetres. Stocks hug both Atlantic basins but denser eastward from Biscay to Spitzbergen, with discrete North Sea, Faroe, Iceland, and Norway populations and western centres from Cape Cod to the Grand Banks.
Demersal fish of rocky to shelly bottoms between roughly 10 and 450 metres prefer 4–10 °C water and concentrate at 80–200 metres. Males mature at about four years, females five—except faster North Sea fish at two and three. A 25-centimetre female may hold 55,000 eggs; a 91-centimetre fish nearly 1.85 million. Spawning peaks March–April in the northeast; eggs hatch in one to three weeks, and larvae settle near 7 centimetres. Lifespan approaches fourteen years. Adults eat urchins, brittlestars, bivalves, and opportunistic fish; seals and larger gadoids eat them.
Eastern Atlantic landings swung around 200–350 thousand tonnes yearly from 1980 to 2017, shifting from Rockall toward the Barents Sea. Western Georges Bank catches once ran 40–60 thousand tonnes yearly before late-1960s collapse. Greenpeace lists haddock red over bottom-trawl harm, while Monterey Bay Aquarium calls it a good alternative and several fisheries hold MSC certificates; ICES judged seven eastern stocks sustainable when assessed. Even parasites dramatize the food web: Lernaeocera branchialis ends life rooted in a haddock's heart after first bleeding a lumpsucker host.
Source: Haddock
