Sea Oddities: Exploring Unusual Fish Species

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Around 71% of the earth’s surface is covered by ocean and up to 80% of all life on earth can be found underneath the waves. While some creatures of the deep are pretty regular, there are others that have a much more fascinating and out-of-the-ordinary appearance. Let’s get to know them a little better.

1. Oarfish (Regalecus glesne)

TikTok has been going crazy lately after a video of a rare oarfish was uploaded; people can’t seem to get enough of these crazy creatures, which are known to be one of the longest ocean fish, measuring up to 36 feet (11 meters)!

Not only are they super long, but oarfish have very slender bodies which give them a rather unique appearance. They get their name from their long dorsal fin which kind of looks like an oar. And similarly to its man-made counterpart, the fin is often used for steering.

They’re not commonly spotted since oarfish typically live at depths between 650 and 3,000 feet (198 and 914 meters) below the surface. And people online have been talking about the mythical connection between oarfish and earthquakes! Yes, you read that correctly – it is claimed that these fish begin to surface and even wash ashore before an earthquake. Although, studies dispute this.

While oarfish are found all over the world, most sightings occur in tropical or middle regions, and the fish was first spotted in the 1700s. However, since they aren’t often sighted in the wild, there is still much to learn about this elusive creature and its behavior.

2. Sarcastic Fringehead (Neoclinus blanchardi)

Imagine having a constantly sarcastic expression on your face; well that’s the fate of the sarcastic fringehead whose facial expression gives it its name as well as its exaggerated displays when trying to fend off one of its own.

These fish, found at shallow depths in the North Pacific, are known to be extremely territorial and have a line of sharp teeth that they’ll use to attack, although not without snapping their jaws first as a warning. When doing this, their mouths open extraordinarily wide, much larger than their heads, and that fringe makes them look almost prehistoric.

But their mouths aren’t just used as a threat, this species will interlock its mouth with a potential mate in a very strange courtship ritual. Males will also do this when fighting for territory until one is able to bite the other and show dominance.

Sarcastic fringeheads are not large fish, typically only growing to around 6-10 inches (15-25 cm). They are very effective ambush hunters that benefit from camouflage, allowing them to strike at small crustaceans. In a year, a single fringehead can consume up to 13.5 times its own body weight.

3. Mola Mola (Mola mola)

A fish that can weigh up to 5,000 lbs (2,268 kg), the mola mola is considered to be the heaviest bony fish in our oceans. Sometimes called the ocean sunfish, this species has a large, flat body and doesn’t have a tail but rather a wavy-looking end to its body. What’s more, while it is considered a bony fish, the mola mola’s skeleton is so small that it makes it appear floppy.

You might think that the sunfish takes its name from its (relatively) rounded shape, but you’d be wrong. They actually get this nickname from the fact that they’re regularly spotted sunbathing near the surface of the water.

Mola mola are found all over the world in both temperate and tropical oceans. It’s thought that their lack of swimming ability causes this wide distribution since they’re often carried along on the current. However, the species is known to migrate in search of the perfect water temperature and can travel up to 5,000 miles (8,047 km) in the space of a few months. 

You’d think that all that traveling and the sheer size of these fish, which can typically reach a size of about 6.6 feet (2 meters) in length, would need a lot of food. However, they tend to stick to smaller gelatinous creatures such as jellyfish as well as small crustaceans and fish.

4. Upside-Down Catfish (Synodontis nigriventris)

The upside-down catfish is a small species that only grows to around 4 inches (10 cm) and is found in the wild in the Central Congo River Basin. That said, they’re a popular aquarium pet, not only because of their size but also their habit of swimming upside down, which is where they get their name.

The reason for this odd behavior is that the mouth of the upside-down catfish faces downwards, which makes it more efficient for feeding from the surface of the water. However, they’ll also swim this way to help themselves blend in with the surface, preventing predator attacks.

They even lay their eggs upside down, laying them on the roof of a cave or, in the aquarium, on the inner roof of upturned flower pots and ornaments.

The upside-down catfish is not only a unique species but a very useful one since its consumption of small invertebrates and algae helps with nutrient cycling.

5. Flashlight Fish (Anomalops katoptron)

There are lots of ocean creatures that use bioluminescence and for various reasons like attracting a mate or to look threatening. However, the flashlight fish uses its ability to create its own light to hunt for prey.

Since the flashlight fish are found at great depths of up to 1,300 feet (396 meters) in the western and central Pacific Ocean, light conditions down there aren’t great. This ability to shine a blue-green light from an organ under the eye allows them to hunt in the dark. And it’s this shimmering light that earns them their name as it looks as though they’re carrying a flashlight.

However, they’re not actually classed as deep-sea fish and are one of the only known species to possess bioluminescence outside of the deep ocean. They’re also a viable species for the aquarium.

Their light naturally syncs with day and night. Because of this, flashlight fish are typically nocturnal and they’ll also use their unique glow to communicate with other members of the same species. What’s super interesting is that these fish are able to control the intensity of their glow and even turn it off when they need to save energy.

6. Viperfish (Chauliodus spp.)

Viperfish are long, slender fish that grow to around 11.8 inches (30 cm) in length, and are found all over the world’s oceans at depths ranging between 1,000 and 2,000 feet (305 and 610 meters). Despite the high pressure and low light conditions down here, viperfish are perfectly adapted and even possess a bioluminescent organ near the other which they use to draw in unsuspecting prey.

In terms of hunting, they’re also equipped with a series of needle-like teeth which not only make it look like a predator but help it to capture prey as it opens its super wide mouth. Even while the mouth remains open, the two long front teeth create something of a cage. Amazingly, they’re able to take on prey much larger than themselves owing to their wide-opening jaws and stretchy stomachs.

While these fish might look like something out of a horror movie, they pose very little danger to humans since we rarely come into contact with them.

7. Longnose Batfish (Ogcocephalus corniger)

The longnose batfish has a triangular-shaped body with pectoral fins that give it the appearance of having wings. Another interesting feature is its long snout with red to orange lips at the end. However, despite this seemingly efficient mouth, the longnose batfish actually feeds on small prey, including worms and crustaceans.

When it comes to swimming, you’d think those dorsal fins were pretty effective but instead, the batfish uses them to crawl along the sea bed. And they’re not fussy about the conditions since they’re easily able to adapt to everything from mud and sand to coral. Because of this, longnose batfish are found at varying depths in the western Atlantic Ocean.

Longnose batfish also use their snouts during mating, and the males will use it to touch the female’s genitals to signal their interest. Those large red lips are also believed to be used to make individuals more attractive to potential mates.

8. Black Swallower (Chiasmodon niger)

The black swallower is an amazing species if only for its ability to live at depths of up to 10,000 feet (3,048 meters) below the water’s surface! It’s found in both tropical and sub-tropical waters and, although we might not always see them, they’re actually one of the most common fish in the North Atlantic.

What’s fascinating about the black swallower is that it has a highly expandable stomach that prominently hangs from its underside. Because of this, these fish are able to consume prey much larger than they are; twice their own size, in fact! However, it isn’t unheard of for black swallowers to get greedy and attempt to eat even bigger prey, but this almost always spells disaster and can cause the stomach to burst. It was because of this, and the resulting gas causing the fish to float to the surface, that the species was first discovered.

Black swallowers will wait in the darkness and are effectively camouflaged owing to their dark coloration. Here, it lies in wait for bony fish and then swings its flexible jaw open to gobble them up.

9. Long-Nosed Chimera (Harriotta raleighana)

Sometimes called the spookfish, the long-nosed chimera was first discovered in the late 1800s, but it remains largely unseen because it lives at depths of up to 6,000 feet (1,829 meters). These fish are usually found in temperate oceans and are actually members of the same group of cartilaginous fish that sharks and rays belong to.

What’s special about the long-nosed chimera is its unique appearance. It has large, almost wing-like pectoral fins and a tail like a whip. It also features a long snout and rounded black eyes that give it a truly ethereal look. Their dorsal fins are tipped with a mildly toxic spine, which may pose a risk to humans.

Living in the dark depths of the ocean, it’ll come as no surprise that the spookfish has bioluminescent abilities. As well as this, they have very concentrated nerve endings in the snout that help the fish to hunt in dark conditions.

During reproduction, females lay eggs in pairs in a web-like structure which is commonly referred to as a mermaid’s purse.

10. Coffinfish (Chaunax spp.)

The coffinfish is certainly an extraordinary-looking animal whose unique shape, that looks like an old-fashioned coffin, is what earns it its name. This is a deep sea species that can live at depths of up to 6,000 feet (1,829 meters) and is found only off the eastern coast of Australia.

As well as its uniquely shaped body, the coffinfish also has flaps of flesh that give it the appearance of having wings. But these fins are not used for swimming and instead provide the fish with stability as it sits on the ocean floor.

However, their unusual appearance serves a purpose, helping the fish to camouflage among the sea bed and rocks. It is here that they will lie in wait for passing prey, like small crustaceans. They have small lures located above the snout that effectively bring prey right into their mouths. What’s more, they have lateral line canals along their bodies that help them detect movement so they know when prey is near.

11. Fanfin Seadevil Angler (Caulophryne jordani)

The fanfin seadevil angler takes its name not only from its spooky appearance but also because it has a lure, just like an angler, which it uses to attract prey.

These fish are found at incredible depths of up to 13,000 feet (3,962 meters) and, like other deep-sea species, are capable of producing their own light using bioluminescence in the form of a light lure that hangs down from the head.

They have rounded bodies, elongated snouts, and huge fanned tails as well as a massive distensible mouth that remains open as unsuspecting prey swims towards it. The upper jaw is much longer than the lower jaw and features flaps that fold down over either side to trap prey.

However, the females are much more elongated than the males, so it’s not hard to tell the difference.

12. Goblin Shark (Mitsukurina owstoni)

The goblin shark is an incredibly strange-looking fish that’s found in the depths of the ocean up to 4,000 feet (1,219 meters) below the surface. For this reason, it’s rarely seen by humans and is only usually spotted during research for other things.

With a prehistoric appearance and no other living relatives, the goblin shark is described as a living fossil. Its only known relative is the Scapanorhynchus fossil and much is yet to be learned about the species. However, we do know that, living in the deep east Atlantic and Indian Oceans, this species is adapted to hunting in low light conditions. The eyes contain specialist retinas that allow the goblin shark to detect bioluminescent prey. And it’s not fussy about what it eats, scouring the ocean floor for anything that might cross its path.

When searching for prey, the goblin shark uses its long pointed snout filled with sensory organs and when prey is detected, those beak-like, tooth-filled jaws extend to quickly capture the victim.

We really don’t know much about the mysterious goblin shark, but scientists believe it is a sluggish swimmer that’s most active at dusk and dawn. While the fish doesn’t have any natural predators, it is sometimes caught by fishermen in Japan.

13. Longhorn Cowfish (Lactoria cornuta)

Found in the coral reefs of the Indo-Pacific regions, the longhorn cowfish is a species of boxfish. It has two long horns at the front of the head that resemble those of a bull, which is where the fish takes its name.

Longhorn cowfish are a small species and are a popular aquarium pet but in the wild, whilst small, they’re actually very well defended against predation thanks to their bony-plated bodies. Their horns are also used to fend off threats, and they may also blow up their bodies (they’re related to pufferfish), so it’s much more difficult for predators to eat them.

Cowfish can often be seen feeding on algae and small invertebrates around the coral reef, where they are largely solitary creatures. Their feeding habits are hugely beneficial to the reef as they prey on invertebrates that would otherwise destroy it, blowing sand with puffs of water in order to access them.

In some instances, cowfish can grow up to 19.7 inches (50 cm) in length and are typically yellow to olive in color with no obvious difference between males and females.

14. Paddlefish (Polyodontidae family)

Another fish that is called a living fossil is the paddlefish as its evolutionary history can be dated back to prehistoric times. In fact, fossil records indicate that this fish may even be older than the dinosaurs and are thought to have been around for at least 300 million years.

The paddlefish is a very easy to identify fish thanks to its long snout, known as a rostrum which is used during feeding. Not only do they use their sword-like rostrums to sift through the sediment on the ocean floor, but they’re also packed with electroreceptors that allow the fish to detect the presence of prey. Being filter feeders, their main diet consists of plankton.

Paddlefish are, unlike most of the other creatures on this list, a freshwater species that are largely found in Asia and North America. Sadly, in the last half a century, paddlefish numbers have declined owing to overfishing and other factors.

15. Red-Lipped Batfish (Ogcocephalus darwini)

Found around the Galapagos Islands, the red-lipped batfish is a bottom-dwelling species that has adapted to use its pectoral fins for walking as opposed to swimming. These unusual creatures have a similar body shape to the longnose batfish that I talked about earlier, but their bright red lips are much more prominent and that is what makes them unique.

It is believed that this feature is intended not only for attracting prey, like small invertebrates and fish, but also as a way of communicating with other members of the same species. During mating season, after breeding, the female will not lay her eggs and leave them but rather carry them in a pouch, which is unusual in fish species.

During hunting, camouflage is essential for the red-lipped batfish that will hide among the rocks or sand on the seafloor, hidden by its light brown or grayish color. But they’re not small fish and can grow to as large as 15.7 inches (40 cm). What’s more, they can live as long as 12 years in the wild!

16. Blobfish (Psychrolutes marcidus)

The blobfish has (unfairly, I believe) been dubbed the ugliest fish on the planet. But what’s interesting is that they only take on that gelatinous, blobby appearance when they’re taken out of the water. When submerged, they actually look very similar to other fish. That’s because they aren’t bony fish and so rely on the water pressure to retain their shape.

This is pretty effective since they live at depths of up to 4,000 feet (1,219 meters), and their jelly-like body allows it to adapt to the extreme pressure at this depth.

Blobfish have become something of a pop culture symbol and they were actually only discovered back in 2003. However, scientists believe that some individuals can live for over a century because they don’t have any natural predators and have a very slow growth rate.

Not much is known about blobfish behavior, especially relating to mating but we do know that they are opportunistic hunters that will eat any prey that floats close enough to them.

17. Barreleye Fish (Macropinna microstoma)

If there was a creature under the waves that looked as though it had come from another planet, it would be the barreleye fish. With a transparent head filled with fluid, it looks like something out of a Steven Speilberg movie. But, these incredible fish can actually be found swimming at depths of up to 2,600 feet (792 meters) in the North Pacific Ocean. There are more than 20 fish within this genus.

And it’s not just the head that makes the barreleye fish look extraordinary; it also has a pair of eyes within the fluid that point upwards, allowing the fish to pick up on bioluminescent prey swimming above it. However, research shows that those eyes are moveable, and the fish does this when it wants to look ahead and focus on its current meal, which it eats via tube shaped nostrils. Weird!

The benefit of the transparent head and strange eyes might be lost on some but when you think about it, it’s a really clever adaptation for life at the bottom of the ocean where light is extremely limited. However, since these fish do live so deep under the water, they’re a rare sight for humans.

18. Tripod Fish (Bathypterois spp.)

The tripod fish is the species on this list that lives the furthest down in the ocean at depths of up to 16,500 feet (5,029 meters). Life in these conditions isn’t easy, but the tripod fish is perfectly adapted, and one of the ways it survives here is by taking on a tripod-like stance that allows it to conserve energy. The fact that it also has a very slow metabolism also comes in handy.

For all intents and purposes, the tripod fish, sometimes called the spider fish, looks like any other regular fish if it weren’t for the long, slender pelvic fins that act as the tripod ‘legs.’ When taking on this position, the fish has limited need to swim and that’s what saves energy. What’s more, while standing like this, all the fish has to do is wait for food to pass by.

Since it’s so dark down in the abyss, some species of tripod fish are equipped with a bioluminescent lure on the snout, which is an effective way to draw in prey.