Deep-sea fish
Deep-sea fish live in ocean waters below the sunlit zone, where darkness, cold, and high pressure shape how they survive.
Bioluminescence: The production and emission of light by living organisms through chemical reactions or symbiotic microbes. Many deep-sea fish use biological light to lure prey, communicate, or avoid predators.
Deep sea: The part of the ocean beyond the continental shelves, characterized by darkness, cold, and high pressure. Deep-sea fish are defined by their residence in this broad ocean environment.
Deep-sea exploration: The investigation of ocean regions beyond the reach of ordinary diving, using submersibles, instruments, and sampling tools. Exploration has revealed fish adapted to habitats that were once inaccessible to observation.
Anglerfish: A group of fishes whose members include deep-sea species that use a modified dorsal fin as a lure. Some deep-sea anglerfish attract prey with a luminous lure and exhibit extreme sexual dimorphism.
Osmoregulation: The regulation of water and dissolved-ion concentrations within an organism. It helps explain how fish maintain internal balance in cold, saline deep waters.
Mesopelagic zone: The ocean layer roughly 200 to 1,000 meters deep, where sunlight fades into darkness. Many fish associated with the deep sea inhabit this dim transition layer.
Remotely operated underwater vehicle: An underwater robot controlled from a surface vessel through a tether. ROVs record deep-sea fish in place without bringing them to the surface.
Vampire squid: A deep-sea cephalopod with webbed arms, large eyes, and adaptations for low-oxygen waters. Despite its name and habitat, it is a mollusk rather than a fish.
Buoyancy: The upward force exerted by a fluid on an immersed object. Gas-filled swim bladders become difficult to use as pressure rises with depth.
Bathypelagic zone: The open-ocean layer roughly 1,000 to 4,000 meters deep, with no sunlight. Its perpetual darkness and intense pressure shape many deep-sea fish communities.