Melanogrammus aeglefinus, commonly known as haddock, is a marine fish found in the North Atlantic Ocean. Recognizable by its silvery body, dark lateral line, and distinctive black 'thumbprint' mark above the pectoral fin, the haddock inhabits cold, deep waters, feeding on invertebrates and small fish. It plays a crucial role in the marine ecosystem as both prey and predator.

Melanogrammus aeglefinus, commonly known as the haddock, is native to the North Atlantic Ocean. Its geographical distribution extends from the eastern coast of North America, including the Gulf of Maine, up through Canada to Greenland. In the eastern Atlantic, it ranges from Iceland and the Barents Sea down to the Bay of Biscay in Europe.

Haddock typically inhabit cold, temperate marine waters. They are predominantly found on continental shelves at depths ranging from 40 to 300 meters, although they can occasionally be found at depths up to 450 meters. The water temperature in these areas usually ranges from 2°C to 10°C. Haddocks prefer sandy, gravelly, or muddy substrates where they can find food.

Haddock occupy a benthopelagic niche, feeding primarily on benthic organisms such as mollusks, crustaceans, and echinoderms. They also consume fish eggs and larvae. Their role as both predator and prey in the marine ecosystem helps regulate the population dynamics of various marine species. Haddocks are adapted to their cold-water environments with physiological traits such as antifreeze proteins that prevent ice formation in their tissues.