Atlantic horse mackerel

What it is

This slender, compressed fish belongs to the jack family. It features a large head with a projecting lower jaw and a well-developed adipose eyelid. Two dorsal fins sit on its back, the second being longer than the first. A distinctive curved line of bony scutes runs from head to tail, giving the species its rough-tailed name. The body is dark blue above, with silvery flanks and a white belly. A dark spot marks the operculum. Adults typically reach 25 cm, though they can grow to 60 cm and weigh 1.5 kg.

Where it lives

Its distribution covers the north and eastern Atlantic Ocean, extending into the Mediterranean, Sea of Marmara, and Black Sea. In the Atlantic, it ranges from Norway down to South Africa, potentially reaching Mozambique along the Indian Ocean coast. Records exist for Cape Verde, but these are likely vagrants. The species inhabits sandy substrates at depths between 100 and 200 metres, though it has been found as deep as 1,050 metres. It also appears in surface waters occasionally.

How it lives

This migratory species moves north in summer and returns south as temperatures drop. Juveniles often shoal with Atlantic herring and other horse mackerels, sometimes sheltering in jellyfish tentacles. Their diet consists mainly of copepods, shrimps, small fishes, and squids. Crustaceans form the largest part of their food intake year-round. Larger individuals over 17 cm feed largely on fish larvae. Stomach content studies in the Aegean Sea revealed 60 different prey species, showing little seasonal variation in dietary habits.

Breeding and life cycle

Spawning timing varies by region. The western stock spawns from Ireland to the Bay of Biscay in early spring. The North Sea stock breeds in summer in the southern North Sea. Off Mauritania, spawning peaks between November and January. Females release eggs in batches, with each batch containing up to 140,000 eggs. The eggs and larvae are pelagic. Spawning is indeterminate, meaning total egg production depends on changing conditions during the season. Females typically begin breeding between two and four years of age.

Fish and people

Commercial fisheries target this species using trawls, longlines, and purse seines. Major catches occur in the Netherlands and Ireland. The flesh is oily and delicate, rich in omega-3 fatty acids. It is consumed fresh, frozen, salted, dried, smoked, or canned. Cooking methods include frying, broiling, and baking. In Iberia, it is prepared as escabeche. Some exports go to Japan for sushi under the name aji. It is also an important ingredient in Sicilian cuisine. Nutritional value includes high protein and moderate fat content.

Status and threats

The IUCN lists the species as Vulnerable. While European populations remain stable, declines exceeding ninety percent off West Africa have driven an overall drop of 35–40 percent over three generations. The International Council for the Exploration of the Sea considers the population below safe biological limits. Fishing pressure has remained high since 2006, with low recruitment observed since 2004. Calls for specific management plans in the North Sea have not yet resulted in defined objectives.

Questions people ask about Atlantic horse mackerel

Good reading and sources

• Atlantic horse mackerel on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data