Chub mackerel

What it is

This small mackerel reaches lengths of roughly thirty-six centimetres. Its body displays a silvery sheen with dark mottled blotches along the lower sides. The eyes are notably large compared to related Atlantic species. A well-developed swim bladder connects to the esophagus, a trait absent in true mackerels of the genus Scomber. The first dorsal fin contains nine or ten spines, fewer than the eleven or more seen in Atlantic counterparts. Dorsal fins sit closer together on the back. The fish exhibits countershading, blending with sunlight and wave patterns to avoid predators.

Where it lives

Populations span the Indo-Pacific region extensively. In the eastern Pacific, they range from Southeast Alaska to central Mexico. They inhabit coastal zones within thirty-two kilometres of shore, preferring water temperatures between ten and twenty-two degrees Celsius. Adults occupy deeper banks down to three hundred metres, while juveniles stay near sandy beaches or kelp beds. A small population exists in the Atlantic off South Africa. They generally remain within twenty miles of the coast, avoiding open ocean depths except during specific life stages.

How it lives

These fish form large schools alongside other pelagic species like sardines. They feed greedily on zooplankton, copepods, and crustaceans. Larvae consume rotifers and even smaller larvae, eating up to eighty-seven percent of their body weight daily. Adults target mysids and euphausids. This diet makes them crucial forage fish for marine predators such as sea lions, pelicans, and cetaceans. Their populations fluctuate rapidly based on coastal upwelling events that boost plankton availability. They exhibit indeterminate batch spawning, releasing multiple egg batches throughout the breeding season.

Breeding and life cycle

Spawning occurs when water temperatures reach fifty-nine to sixty-eight degrees Fahrenheit. Females produce between one hundred thousand and four hundred thousand eggs per season. Breeding peaks from April through August but can extend from March to October. Spawning intensity correlates with seasonal upwelling, ensuring sufficient plankton for larval survival. Ripe translucent eggs may appear alongside unripe ova in early development stages. Individuals can reproduce by age four and live up to eighteen years. Multiple spawning events happen annually in regions like California.

Fish and people

Fishermen catch this species year-round, peaking between June and November. Commercial fisheries operate primarily in California and Mexico using purse seines. The catch peaked at over three million tons in 1978 before declining. It is canned, sold fresh, used as bait, or processed for pet food. In Sicilian cuisine, it appears pickled, frozen, or marinated raw. Koreans prepare it in jorim dishes with tofu and vegetables. Nutritionists note its high protein and omega-3 content, though heavy metal levels may vary. Recreational catches in California averaged over fourteen hundred tons annually in the late twentieth century.

Status and threats

The species faces no immediate global extinction risk. However, local populations respond sensitively to environmental changes like upwelling shifts. Overfishing pressures have reduced historical peak catches since 1978. Management strategies focus on sustainable harvest levels given its role as a primary prey source. Bycatch remains low due to targeted netting methods. Climate fluctuations affecting plankton density directly impact recruitment success and overall stock health in various regions.

Relatives and look-alikes

It closely resembles the Atlantic chub mackerel. Differences include eye size, dorsal spine count, and lateral coloration patterns. The Atlantic species lacks the mottled lower sides and has more dorsal spines. Another Indian Ocean species, Scomber indicus, was identified separately in 2015. True mackerels in the genus Scomber lack the swim bladder connection found here. These distinctions help separate the chub mackerel from similar pelagic hunters in shared habitats.

Questions people ask about Chub mackerel

Good reading and sources

• Chub mackerel on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data