Haddock

Haddock (Melanogrammus aeglefinus) is a member of the cod family Gadidae, found in cold continental shelf waters of the North Atlantic on both the European and North American coasts. It is closely related to Atlantic Cod but is a distinct species with its own characteristic markings, most notably a dark lateral line and a rounded dark spot near the pectoral fin, sometimes called the "devil's thumbprint" in folklore. Haddock has long supported significant commercial fisheries and has experienced periods of population decline followed by recovery under managed fishing quotas in different regions. It remains one of the more recognizable and widely distributed gadid species across the North Atlantic shelf.

Haddock can be reliably separated from Atlantic Cod and Pollock using a few clear markers.

• Lateral line: solid black, sharply contrasting against the silvery body, unlike cod's pale lateral line
• Marking: a distinct dark round blotch above the pectoral fin, absent in cod and pollock
• Body: slender, moderately deep, dark grey-purple above fading to silvery-white below
• Fins: three dorsal fins, two anal fins, single small chin barbel
• Size: typically 40-70 cm The combination of a black lateral line and the dark pectoral "thumbprint" spot is the single most reliable way to identify Haddock at a glance.

Haddock are found in cold continental shelf waters of the North Atlantic, ranging from the eastern coast of North America, including the Gulf of Maine and Grand Banks, across to the North Sea, Iceland, and Norwegian coasts. They typically inhabit depths between 40 and 300 meters, favoring sandy, gravelly, or muddy bottoms rather than rocky reef structure. Haddock prefer relatively cold water and show seasonal depth movements, moving to deeper offshore water in winter and shallower banks in warmer months. Juveniles often settle in slightly shallower nursery grounds than adults before moving into deeper shelf habitat as they mature.

Haddock are primarily bottom-feeding fish, using their chin barbel to detect buried prey such as worms, small mollusks, brittle stars, and crustaceans in soft sediment. They often form loose schools, particularly juveniles and during spawning aggregations, moving together across shelf banks in search of food. Spawning occurs in late winter through spring at established grounds, where females release large numbers of pelagic eggs that drift with currents before hatching. Haddock grow relatively quickly compared to cod and can live over a decade. As an abundant mid-shelf species, they serve as an important prey source for larger fish, seabirds, and marine mammals, and as a key indicator species in North Atlantic fisheries management.