Melanogrammus Aeglefinus, commonly known as Haddock, is a salt-water fish that resembles the cod and shares commonalities such as a chin barbel, two anal and three dorsal fins. In Greek, “Melanogrammus” translates to “black line” for the distinct line that Haddock possesses. The name “Aeglefinus” is derived from églefin, the French word for Haddock.

It is the sole surviving species of its genera and a kind of ray-fin fish that belongs to the real cod family. The main visual difference that distinguishes Haddock from Cods is the lighter colors and dark patches. Among the fish taken by trawls, Haddock may be cod’s commercial rival in significance.


Haddock has the conventional extended, sloping structure of cod family members. It is most readily recognized by the characteristic marking on either side of the body and the dark or purple line tracing along the back. These features stand out sharply against the light or silvery body. 

Haddock with its notable thumbprint on the side
Haddock, with its notable thumbprint on the side

The Haddock has a tiny mouth that does not reach underneath the eyeball, and because the top and bottom profiles of its face are both slightly convex and vertical, the snout has a distinctive wedge-shaped aspect. On the chin, Haddocks have a little barbel. The first of the three dorsal fins is triangular in form. All in all, Haddock is a moderate fish, weighing around 3-5 lbs and ranging in length from 1-3 ft.


Haddocks are carnivorous fish, and the majority of their food is invertebrates that move slowly along the seafloor. They prey on fish, including herring, capelin, hake, and eels, in addition to gobies and sprats. In particular, during the winter, shellfish, sea urchins, brittle stars, and worms are essential prey items for Haddock.

Haddocks rely mostly on copepods, krill, decapod larvae, and copepods when they are still in their larvae stage. Although they continue to consume pelagic species like krill, they eventually rely on benthic invertebrates to get more and more significant as they develop.


Haddocks are groundfish that inhabits typical environments such as gravel, clay, and firm or smooth sand. They are bottom-dwellers across the board. Haddocks thrive in seas that are between 100-500 ft deep and thrive in temperatures around 45° Fahrenheit. While bigger adults are more prevalent in deeper water, juveniles are more numerous in shallower depths along banks and shoals.

Typical Haddock at depths where light doesn't reach
Typical Haddock at depths where light doesn’t reach

In the North Sea, especially in the northern portion, as well as farther north to the Faroe Islands, Iceland, and the Barents Sea, Haddock is in great abundance. Haddock is also plentiful on the western side of the Atlantic, from Cape Cod to the Cabot Strait, and there are significant populations on the southern part of the Grand Banks of Newfoundland.


Haddock spawn mostly from February to April, at which time the adult fish migrate to shallower depths to breed. The bigger females may lay up to 3 million eggs during a mating season, whereas the typical female produces around 800,000. The male Haddock will fertilize the eggs when the female releases big clusters of her eggs close to the ocean floor.

The eggs then rise to the top along the water column and float for around 15 days along the ocean currents. Haddock moved to an adult diet and swam deeper after gaining a few inches. Haddock may live up to ten years and require one to four years to reach sexual maturity.


Natural predators of Haddock include spiny dogfish, skates, and gray seals, as well as other groundfish, including cod, pollock, cusk, and hakes. Haddocks have grown to be one of the most sought-after species for recreational anglers, as well as the most common fish that is used for food.

Caught Haddock with its light underside exposed
Caught Haddock with its light underside exposed

Recent stock evaluations revealed that no Haddock’s species were overfished and that no exploitation was taking place. Haddock mortality is at an all-time low, while biomass is at a record high.

Facts about the Haddock

  1. The largest Haddock measured 37 in and weighed around 24 lbs.
  2. For defense, Haddocks swim in big schools.
  3. Haddocks are able to survive in deep, icy waters.
  4. Haddocks are short-distance “sprinters,” able to swim very fast and avoid predators.
  5. Haddock can exist in the wild for more than a decade.


What is the difference between Haddock, and Codfish?

Cod is a greenish-brown or dark fish with spots. Haddock has mucus-coated scales that are gray or black, as well as a dark spot above the pectoral fin known as St. Peter’s imprint, the Devil’s fingerprint, or plain the fingerprint. Due to the larger, fatter, and thicker filets, cod is somewhat more expensive since it contains more flesh.

When is Haddock fished?

Haddock is harvested in multispecies fisheries with other groundfish species like cod and halibut and is often captured using equipment including Danish seine nets, trawlers, long lines, and gill nets. It is particularly caught in the eastern Atlantic and in the Northern Sea due to high population concentrations.

How deep do Haddock live?

Haddocks typically inhabit deeper seas between 130-450 ft underwater, with larvae often inhabiting the lesser depths. The deepest Haddock ever found was collected during a bottom trawl sweep at a depth of more than 1000 ft.

Is there a season for Haddock?

Seasonally migratory, haddock are most common in coastal New England during summertime in the relatively shallow waters of the Gulf of Maine. Spawning season is between March and April. The most fruitful haddock spawning grounds may be found in the Northwest Atlantic on Eastern Georges Bank.

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