What Is a Pelagic Fish?

The basic definition of pelagic fish is fish that live in the pelagic zone. This is the vertical column of open water in seas and large lakes, excluding the areas closest to the substrate. It includes the areas nearest the sea surface, including the photic zone, where sunlight can penetrate.

Different layers of the pelagic zone have different characteristics, greatly influenced by the amount of sunlight they receive. Other factors include salinity, the presence of minerals and the pressure at different depths. The fish that live in the pelagic zone can be very different from each other, but they also share certain common characteristics. Pelagic fish:

• Constitute fundamental links in food webs, with some being food for many species and others acting as apex predators. Likewise, they are responsible for transferring a large part of the energy flow in pelagic environments.
• Many form synchronized schools. Doing so increases hydrodynamic efficiency, improves their success in catching prey and acts as a defense. Learn more about how fish group with our article on what is fish shoaling?
• Are species of great economic importance to the artisanal and industrial fishing sectors. Their fishing must be regulated by various nation-states to avoid overexploitation and promote their protection and conservation.
• Many undertake periodic migrations related to reproduction. Some release their eggs or larvae upstream, helping them reach refuge sites and increasing their chances of survival.

Unlike demersal fish, which live on or near the seabed, pelagic fish spend their lives in open water. Some remain near the surface, while others move between depths in search of food or suitable conditions.

Now that we know some of their characteristics, here are some types and examples of pelagic fish:

The yellowfin tuna (Thunnus albacares) is a large, strong and fast pelagic fish. It usually lives in warm tropical and subtropical waters around the world, except for the Mediterranean. It lives in the epipelagic zone at depths of up to 100 m, largely because of its sensitivity to changes in oxygen concentration. Its fusiform body is metallic blue, but it has a longer second dorsal fin and anal fin, both of which are yellow. This helps distinguish it from other tuna species. Like other tuna, it is adapted for sustained swimming in open water and often travels in schools.

Due to overfishing, it was listed by the IUCN as ‘Near Threatened’. However, recent conservation efforts have meant that it moved to the category of ‘Least Concern’ in the latest update to the IUCN Red List^[1].

Like the yellowfin tuna, the Atlantic bluefin tuna or giant bluefin tuna (Thunnus thynnus) is a large pelagic fish found in all the world's oceans except polar waters. It is a powerful swimmer that can reach depths of up to 1,000 meters. It measures up to 3 m in length and weighs up to 700 kg. Its seasonal movements between feeding and spawning grounds can take it across large stretches of ocean.

Because it has great commercial value, overfishing of this species threatens its survival. This is why various organizations, such as the International Commission for the Conservation of Atlantic Tuna (ICCAT), work to regulate its fishing and help ensure its protection.

Swordfish (Xiphias gladius) is a pelagic, migratory and cosmopolitan species with a wide distribution. It is a voracious predator whose diet is mainly based on cephalopods, fish and crustaceans. Females are larger than males, and some specimens can weigh up to 540 kg. The fusion and extension of the bones of its upper jaw form a beak similar to a sword, hence its common name. It is also known as the broadbill. Swordfish often hunt at depth during the day and move closer to the surface at night.

Swordfish are among the few fish that can maintain their internal body temperature above the ambient water temperature (i.e. they are homeotherms). While the species is listed as ‘Near Threatened’ by the IUCN globally, its North Atlantic populations are endangered.

Known as chub mackerel or Pacific mackerel (Scomber japonicus), this is a pelagic coastal species with a cosmopolitan distribution. It lives in the world's temperate oceans at depths of up to 300 m. It is opportunistic and feeds on zooplankton, small fish, mollusks, cephalopods, polychaetes and larvae of various animal groups. It has a small head and scales, and its back is greenish blue with sinuous dark bands common to all types of mackerel. Its meat is mainly used to make preserves. Schools may move closer to shore when food is plentiful. Mackerel was assessed by the IUCN in 2022 and is listed as ‘Least Concern’.

Another pelagic fish commonly consumed as food, the European pilchard (Sardina pilchardus) has an elongated, platinum-colored body with gill rakers on its gills. These are extensions that allow it to collect plankton as it swims. It has a short life cycle and makes vertical migrations during the day to feed. Reproduction occurs in the winter months, when the water temperature is colder. Its schooling behavior can help reduce the risk of being caught by predators.

Along with other smaller species, pilchards are a key link in food chains. They are prey for various apex predators, such as swordfish (Xiphias gladius). According to the IUCN, the species is of ‘Least Concern’.

Learn about the animals that feed on pelagic fish with our article on the different types of piscivorous animals.

Also known as the dorado or the common dolphinfish, the mahi-mahi (Coryphaena hippurus) is a large pelagic fish distributed in temperate and tropical seas. It is an epipelagic predator that feeds on cephalopods, seahorses and fish, among other prey. Its body can reach a length of 1 m and has very striking blue, green and yellow colors. Its long dorsal fin, which extends along much of its back, is another distinctive feature.

Mahi-mahi has great economic interest. It is a valuable resource and source of employment for various communities that depend mainly on fishing. Fortunately, the IUCN places it in the category of ‘Least Concern’.

Also known as the Mexican sierra, the Pacific sierra (Scomberomorus sierra) is a pelagic fish species that forms enormous schools. It can move easily and at high speeds thanks to its hydrodynamic body. Its distribution area covers the Pacific Ocean from southern California to Peru, including the Galapagos Islands. Pacific sierra make migratory movements in search of food, mainly small fish such as sardines and anchovies. Their schooling behavior and speed also help them hunt effectively in open water. It is a very important species for artisanal fishing. According to the IUCN, it is of ‘Least Concern’.

The wahoo (Acanthocybium solandri) is an epipelagic fish species that lives in the Atlantic, Indian and Pacific oceans. Its distribution includes the Caribbean and the Mediterranean Sea, mainly in areas far from the coast. Males can measure 250 cm in total length and weigh up to 80 kg. Its long, streamlined body and pointed snout are characteristic features.

This species grows rapidly and reaches sexual maturity early. There is currently no evidence that it has been affected by fishing, although local population depletion may have occurred. For this and other reasons, it is listed as ‘Least Concern’.

Learn more about these types of pelagic fish with our article on whether sharks are blind.

The blue shark or great blue shark (Prionace glauca) is a cartilaginous, viviparous and cosmopolitan pelagic fish distributed in all the world's oceans and found near their various coastlines. It is a voracious predator that feeds on bony fish, sharks, cephalopods and, when the opportunity arises, seabirds.

It can weigh up to 200 kg and measure up to 4 m in length, although its average size is usually 2 m. It is known for long-distance migrations across ocean waters. Because of its migratory habits, its conservation status is difficult to evaluate, but according to studies it is considered ‘Near Threatened’.

Another type of pelagic shark species, the silky shark (Carcharhinus falciformis) is a cartilaginous fish with one of the largest distribution ranges in the world. Despite its relative abundance, its slow reproductive rate and high level of fishing exploitation mean it is now considered ‘Vulnerable’. Females give birth to live young, and the species is a precise hunter, largely due to its incredible swimming ability. It is often associated with offshore waters, though it may also approach coastlines.

Now you know about these types and examples of pelagic fish, you might want to know about other species with our article on different types of venomous fish.

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