Atlantic mackerel

The Atlantic mackerel was first described in 1758 by Swedish zoologist Carl Linnaeus in his 10th edition of Systema Naturae. Linnaeus gave it the scientific name Scomber scomber from the Greek word skombros meaning "tunny" or "mackerel". Because of its wide distribution, the Atlantic mackerel was independently described 6 more times by 5 different scientists between 1814 and 1863. Its specific name was later changed to scombrus by B. B. Collette and C. E. Nauen in 1983.[2] It is differentiated from its congeners in a number of ways, the first being the absence of a swim bladder. Its palatine bone is also wider than other members of its genus and its otolith is oval-shaped where its congeners' are rectangular.[3]

In the eastern Atlantic Ocean there are three stocks differentiated by location and time at which spawning occurs, but studies have not found any distinct genetic differences between these populations. Genetic differences only start to appear at the transatlantic scale, a fact supported by a lack of migration between western and eastern Atlantic populations, whereas eastern Atlantic stocks are known to converge in certain locations like the Norwegian Sea and North Sea.[4]

An 1835 illustration of the Atlantic mackerel.

The Atlantic mackerel has an elongate, fusiform body with a long, pointed snout. The eyes are large and covered by an adipose eyelid, while the teeth are small, sharp, and conical. Scales are also small, with the exceptions of those immediately posterior to the head and around the pectoral fins. These small scales give the Atlantic mackerel a velvet-like feel. The two dorsal fins are large and spaced far apart. The second dorsal fin is typically followed by 5 dorsal finlets, though it can have 4 or 6. The anal fin, which originates slightly behind the second dorsal fin, is similar to it in size and shape and is also succeeded by 5 finlets. The fish's body tapers to a slim caudal peduncle, the end of the fish to which the short but broad tail fin is attached.[5] Its body is steel-blue dorsally with wavy black lines running perpendicular to the fish's length. The rest of its body is silvery-white to yellow and may have darker splotches.[6] It can reach sizes of up to 60 cm (24 in) and has a common length of 30 cm (12 in). Its maximum published weight is 3.4 kg (7.5 lb).[2]

The Atlantic mackerel's native range in the western Atlantic extends from Labrador, Canada to Cape Lookout, North Carolina. In the eastern Atlantic, it can be found from Iceland and Norway to as far south as Mauritania. It is also found in the Mediterranean, Black, and Baltic Seas.[1] Its latitudinal range is 70°N-25°N and its longitudinal range is 77°W-42°E.[2] Its preferred water temperature is above 8 °C (46 °F), but Atlantic mackerel are common in waters as cold as 7 °C (45 °F) and have been found, albeit rarely, in 4.5 °C (40.1 °F) waters.[7] The Atlantic mackerel's common depth range extends from the surface to 200 m (660 ft), but individuals can be found as deep as 1,000 m (3,300 ft).[2]

Atlantic mackerel are migratory fish, spending the spring and summer closer to shore about 32–161 km (20–100 mi) out, with juveniles moving closer in to shore than adults. Occasionally, fish will even enter harbors, and those that do are usually juveniles. In the fall and winter they move farther out and farther south to the warmer waters on the edge of the continental shelf. They first come in to land in North America in April at the southern end of their range, but are found along the coast through their entire range by July. They start moving back out to sea again in September and are completely gone from the coast by December. Food availability increases greatly during the summer, and fish reach a peak for fat tissue in August, a mere four months after their lowest point in April.[7]

The Atlantic mackerel is an active, fast-moving fish that must keep in constant motion to bring in enough oxygen to survive. It swims using short movements of the rear of its body and the caudal fin. Unlike other mackerel, Atlantic mackerel do not leap out of the water unless attempting to escape a predator.[5] They form large schools, consisting of individuals of the same relative size, near the ocean surface during all seasons but winter. Because larger fish have a greater ratio of muscle mass to surface area, schools of larger fish are able to swim more quickly than schools made up of smaller individuals.[8]

Feeding

When feeding on larger prey, schools tend to break down into shoals and individuals find food on their own. When consuming plankton, however, Atlantic mackerel form tight aggregations, open their mouths as wide as possible, and extend their operculums, swimming in a tightly packed school that acts like a series of miniature tow nets. Spaced only about the diameter of a single fish's mouth apart, this formation greatly reduces the ability of plankton to evade capture, as a plankton darting out of the way of one fish is likely to end up in the jaws of another. Copepods make up the majority of the Atlantic mackerel's diet, Calanus finmarchicus being the most abundant.[7]

Atlantic mackerel close-up

Atlantic mackerel.

The Atlantic mackerel is of commercial importance to many Atlantic fisheries, which catch it with purse seines, trawls, gill and trammel nets, and trolling lines. Global annual catch is typically in the range of 1 million tonnes, though a 50% spike in 2014 put this number at nearly 1.5 million tonnes. The United Kingdom and Norway bring in the most Atlantic mackerel, with annual catches coming in at over 166,000 tonnes and 160,000 tonnes respectively.[6] There are three stocks in the eastern Atlantic: one in the south, one in the west, and another in the North Sea. There are two populations in the Mediterranean, one in the east and one in the west.[1] In the western Atlantic there are two stocks, one in the north and one in the south,[7] for which assessments are, according to the IUCN, "highly uncertain".[1]

• Donovan, Moira (18 January 2022). "Holy Mackerel, Where'd You Go?". Hakai Magazine.

• Media related to Scomber scombrus at Wikimedia Commons
• Data related to Scomber scombrus at Wikispecies
• EDF Report on Mackerel – Atlantic Mackerel conservation and contamination report