The World’s Rarest Fish Species and How to Find Them

• 1

  Angler Fish

  

  You almost certainly know what an anglerfish looks like, or at least a female one; they're the large-mouthed, sharp-toothed deep-sea fish with a light dangling from their foreheads. They're so frightening and intimidating in appearance that many subspecies are colloquially known as sea devils. Males look very different to the females, but they might agree with the sea devil moniker; these fish mate by melting and subsuming the males into the female's body, where they become sperm-carrying appendages. Deep-sea anglerfish, called dreamers, are particularly hard to see; many species are classified by only a handful of specimens because of the great depths at which they live in temperate waters around the world.

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• 2

  Devil’s Hole, where the Pupfish are found

  

  In a sense, the Devil's Hole pupfish is very easy to find, as the one place they live is right in their name. Devil's Hole is a unique cave in Death Valley, Nevada, more than 400 feet deep but not yet accurately measured. Its low-oxygen waters are the only home to this unique, iridescent fish, so small they are regularly preyed on by beetles. According to David Thomas, changes in their native environment and declining water levels have seriously threatened their existence. To date, all attempts to establish populations of this pupfish outside of Devil's Hole have failed.

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• 3

  Giant Sea Bass

  

  Though once widespread throughout the eastern Pacific Ocean, giant sea bass now inhabit only a relatively small section along the Californian and Mexican coasts; only around 500 fish are believed to comprise the entire wild population. The reason for this decline is simple and sad: Their massive size – often exceeding seven feet in length and weighing more than 500 pounds – made them a popular target for sport and spearfishermen throughout the 20^th century. Only heroic conservation efforts beginning in the 1970s have saved this species from extinction.

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• 4

  Goblin Shark

  

  While calling it a goblin may be a bit harsh, there's no denying that the goblin shark has a slightly disturbing look, defined by the large mouth that is recessed underneath the fish's snout when not in use. When it's ready to eat, the goblin shark extends this mouth to grab its prey, shocking many first-time viewers of this unusual creature. Most of these viewers are actually watching videos, though, as the goblin shark lives on continental shelves at depths of at least 100 meters, and possibly as deep as 1300 meters. When they are spotted, though, they can be found in the Atlantic, Indian, and Pacific oceans.   

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• 5

  Oarfish

  

  I would love to give you lots of information about this massive and fascinating deep-sea fish, which is believed to be the inspiration for ancient legends of sea serpents, but the truth is that even scientists just don't know very much about it. They aren't believed to be particularly rare, per se, and have been found throughout temperate and tropical ocean waters; they just live so deep and are so reclusive that they're almost never seen alive. Most oarfish specimens are corpses that have washed ashore, as they're known to hang out near the surface when injured, sick, or dying. 

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• 6

  Red Handfish

  

  The red handfish gets its name from its red coloration and the strange way it moves along the seafloor, "walking" on its hand-like pectoral fins. Originally native to several sand reefs around Tasmania, the species is now only found in Frederick Henry Bay, hanging on in two small subpopulations. There may not be more than 20 to 40 specimens left in the wild. This fragmentary, tiny population, along with continued threats from temperature changes, human development, and the encroachment of purple urchins, mean this unique creature is considered critically endangered.   

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• 7

  Sakhalin Sturgeon

  

  The Sakhalin sturgeon has always had a limited range, living mainly in two rivers and some brackish environments in Japan, Korea, and Russia. These sturgeons are believed to follow a similar life cycle to Alaskan salmon, returning up the river each year to spawn and lay their eggs. They were a fairly popular market fish in the 1950s, but a number of factors, including overfishing, pollution, and dams being constructed across the rivers they swam up to spawn every year, meant their numbers declined significantly. There are now believed to be only 20-30 breeding specimens left in the wild, all based in Japan's Tumnin River.  

  Some fish species are so rare that we could not even find corresponding images for them. Like the Ayumodoki (Kissing Loach) – The Ayumodoki or kissing loach is a Japanese fish native to the rivers of Japan's largest island. For centuries, they spawned and lived in the flooded paddies and irrigation ditches of widespread rice cultivation; as the island has urbanized and moved away from rice cultivation, the kissing loach has suffered greatly from loss of habitat. Fewer than 800 are believed to remain in the wild. Only the remarkable efforts of dedicated volunteers have kept this species alive in its native habitat.

  As well as the Ornate Sleeper-ray – Not much is known about the ornate sleeper-ray, which
  was only fully described in 2007, after a first sighting as far back as 1984. They are currently the only member of their genus, Electrolux¸ and have only been documented on four shallow reefs along the South African coast. As the genus name suggests, this species uses electric pulses to stun its prey, usually small worms or crustaceans; the "ornate" in its common name refers to its elaborate brown and yellow patterning and spiraling papillae (mouth appendages). The delicacy of coral reefs, their popularity for recreational diving, and the rampant development along the South African coast are all continuing threats to the species' survival.

  And finally, we have the Tequila Splitfin – The tequila splitfin is named for the volcano that stands over its native range, which was originally much of the Ameco River and its basin in central Mexico. These small, olive-colored fish were believed to be extinct in the 1990s because scientists were unable to find any specimens in this river; it was thought they were pushed out by the introduction of non-native guppies. Ten years later, however, a tiny, fragmentary population was found in a single, 13-foot pool. The fewer than 50 adult splitfins that currently occupy this pool were believed to be the only foothold this species retained in the wild until a successful reintroduction effort earlier this year.  

  The fact is that none of these fish is likely the rarest or most unusual fish in the world;
  more likely than not, whatever animal technically holds that title hasn't been discovered
  yet. Until it is, though, catching a glimpse of one of these hard-to-find beauties will be a
  pretty amazing experience all on its own.

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