Pelagic fish

Pelagic Fish

Pelagic fish swimming in the ocean

Pelagic fish are species that inhabit the pelagic zone of ocean or lake waters – being neither close to the bottom nor near the shore. This zone is typically characterized by open water, and pelagic fish are adapted to life in this environment. They are contrasted with demersal fish, which live on or near the bottom, and reef fish, which inhabit coral reefs.

Characteristics

Pelagic fish are often streamlined and built for speed, as they need to cover large distances in search of food. They tend to have a high metabolic rate and are often migratory. Many pelagic fish are also schooling fish, which means they travel in large groups for protection against predators and to increase their efficiency in finding food.

A large bluefin tuna, a type of pelagic fish

Pelagic fish can be divided into two main groups: coastal pelagic fish and oceanic pelagic fish. Coastal pelagic fish inhabit the relatively shallow and sunlit waters above the continental shelf, while oceanic pelagic fish are found in the deeper waters of the open ocean.

Types of Pelagic Fish

Pelagic fish include a wide variety of species, ranging from small fish like herring and sardines to large predators like tuna and sharks.

Small Pelagic Fish

Herring, a common small pelagic fish

Small pelagic fish, such as anchovies, sardines, and herring, are often found in large schools. These fish are a crucial part of the marine food web, serving as prey for larger fish, marine mammals, and seabirds. They are also important for commercial fisheries.

Large Pelagic Fish

A great barracuda, a large pelagic predator

Large pelagic fish include species such as tuna, mackerel, swordfish, and barracuda. These fish are often apex predators in their ecosystems and are known for their speed and strength. They are highly sought after in commercial and recreational fishing.

Habitat and Distribution

Pelagic fish are found in oceans and seas around the world. Their distribution is influenced by factors such as water temperature, salinity, and the availability of food. Many pelagic fish undertake long migrations, often crossing entire ocean basins.

Sargassum seaweed, a habitat for some pelagic species

The Sargasso Sea is a notable habitat for pelagic fish, where floating sargassum seaweed provides shelter and breeding grounds for various species.

Adaptations

Pelagic fish have evolved a range of adaptations to survive in the open ocean. These include countershading, where the fish's dorsal side is darker than its ventral side, helping it blend into the ocean depths when viewed from above and the sky when viewed from below.

A frogfish camouflaged among sargassum

Many pelagic fish also have specialized sensory organs to detect changes in water pressure and movement, aiding in navigation and hunting.

Importance to Ecosystems

Pelagic fish play a vital role in marine ecosystems. They are a key link in the food chain, transferring energy from plankton to larger predators. Their movements and migrations also contribute to nutrient cycling in the ocean.

Related Pages

• Demersal fish
• Reef fish
• Marine food web
• Fish migration