Open ocean
The open sea, far from land, near the surface. 38 fish on EveryFish so far.
The open ocean, far from land, is the largest habitat for fish near the surface. Its sunlit upper layer, down to about 200 metres, is home to fast, wide-ranging fish: tuna, swordfish, marlin, sailfish, mahi-mahi, flying fish and oceanic sharks. Food is patchy, so many of these fish swim great distances, following currents, fronts and schools of smaller prey across whole ocean basins.
Built for distance
Open-ocean fish are streamlined and countershaded, dark above and silver below. Tunas and some sharks keep their muscles warm and never stop swimming. Swordfish and marlin warm their eyes and brain to hunt in cold, deep water. Sailfish are often called the fastest fish, though measured speeds are lower than the popular claims. The ocean sunfish drifts and dives, eating jellyfish. Flying fish glide above the waves to escape predators.
Fishing the high seas
Tuna, swordfish and sharks of the open ocean are caught by longlines and purse seines, often far from any coast, and are managed by regional tuna commissions. Oceanic sharks, such as the oceanic whitetip, have declined steeply. A United Nations treaty on the high seas, adopted in 2023, came into force in January 2026 and allows marine protected areas to be set up in international waters, which cover nearly two thirds of the ocean.
Still to be written: Atlantic bluefin tuna, Skipjack tuna, Swordfish, Indo-Pacific sailfish, Mahi-mahi, Ocean sunfish, Oceanic whitetip shark, Blue shark.
Further reading
WorldCommon fangtooth
A small, black deep-sea fish with large fangs found worldwide.Other · Open ocean · 1833
WorldViperfish
Deep-sea fish with fang-like teeth and bioluminescent lures in the genus Chauliodus.Other · Open ocean · 1801
WorldMarine hatchetfish
Small deep-sea fish with a distinctive compressed body shape and bioluminescent camouflage.Other · Open ocean
WorldAtlantic footballfish
Deep-sea anglerfish with a glowing lureOther · Open ocean · 1837
WorldSnailfish
A family of marine ray-finned fishes found from shallow coasts to the deepest ocean trenches.Other · Coasts and shelves · 1861
WorldDeepsea lizardfish
A deep-ocean predator with a flattened head and large eyes found in tropical seas worldwide.Other · Deep sea · 1878
WorldRibbonfish
Deep-sea lampriforms with long, tape-like bodiesOther · Open ocean
WorldGlasshead barreleye
Deep-sea fish with mirror-based eyesOther · Open ocean
WorldCrestfish
Deep-sea ribbon fish with a head crest and ink sacsOther · Open ocean
WorldBarreleye
Deep-sea fish with tubular eyes and a light-producing anusOther · Open ocean
WorldBristlemouths
A family of abundant deep-sea fish with bioluminescent organs and bristle-like teeth.Other · Open ocean
WorldLanternfish
Small bioluminescent mesopelagic fish found in oceans worldwide.Other · Open ocean
WorldAnglerfish
Ray-finned fish using a modified dorsal fin ray as a lure to catch prey.Other · Coasts and shelves · 1829
WorldOarfish
Extremely long pelagic fish known for their ribbon-like bodies and association with sea serpent myths.Other · Open ocean · 1772
WorldHumpback anglerfish
Deep-sea black seadevil with a glowing lureOther · Open ocean · 1863
WorldSloane's viperfish
Deep-sea dragonfish with huge teeth and light organsOther · Open ocean · 1801
WorldBlack dragonfish
Deep-sea fish with infrared light and stalked larval eyesOther · Open ocean
WorldGiant oarfish
The world's longest ray-finned fish, known for its ribbon-like body and crimson crest.Other · Open ocean · 1772
WorldBlack swallower
Deep-sea fish that eats prey larger than itselfOther · Open ocean
WorldPacific blackdragon
Deep-sea fish with light-absorbing skin and a glowing chin lure.Other · Open ocean
WorldTripod fish
Deep-sea fish that stands on elongated finsOther · Open ocean
🇯🇵 Japan and 1 moreGiant grenadier
A large deep-sea rattail from the North Pacific.Other · Open ocean
Photo credits on this page
The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.
- Common fangtooth: Brian Suda, CC BY-SA 2.0, source
- Viperfish: NOAA Ocean Exploration, Voyage to the Ridge 2022, Public domain, source
- Marine hatchetfish: Unknown author, CC BY-SA 3.0, source
- Atlantic footballfish: Unknown author, CC BY-SA 2.5, source
- Snailfish: Erin McKittrick, CC BY 4.0, source
- Deepsea lizardfish: Bideault, Public domain, source
- Ribbonfish: Personnel of NOAA Ship DELAWARE II, Public domain, source
- Glasshead barreleye: Adrian Flynn, CC BY 1.0, source
- Crestfish: Unknown author, Public domain, source
- Barreleye: S. Johnsen (Duke Uni.) for courtesy of photos, J. Hlidberg for courtes, CC BY 4.0, source
- Bristlemouths: Unknown author, Public domain, source
- Lanternfish: Emma Kissling, Public domain, source
- Anglerfish: Unknown author, Public domain, source
- Oarfish: Sandstein, CC BY 3.0, source
- Humpback anglerfish: Emőke Dénes, CC BY-SA 4.0, source
- Sloane's viperfish: Gervais et Boulart, Public domain, source
- Black dragonfish: GM. Woodward, Public domain, source
- Black swallower: Unknown author, Public domain, source
- Pacific blackdragon: Unknown author, Public domain, source
- Tripod fish: null, CC BY 4.0, source
- Giant grenadier: Joe Mabel, CC BY-SA 4.0, source