Deep Sea Fish – 15 Of the Most Ununusal

There’s been a lot of talk about the ocean floor recently. But in the science community, this is the norm.

The deep ocean is vast and otherworldly with new discoveries being made daily. Life had to adapt to extreme pressure, temperature, and lack of sunlight, which has led to some incredible organisms, including bacteria, fish, and a plethora of invertebrates.

Unfortunately, none of these fish will ever be able to make their way into the home aquarium. Still, they’re some of the most interesting species ever discovered. Lets look at 15 of the most unusual Deep Sea Fish to be discovered.

Key Takeaways

• There is an incredible amount of life at the bottom of the ocean.
• The better majority of the ocean has yet to be discovered and new species are regularly discovered.
• Deep sea organisms have had to make extreme adaptations to their environments.
• New technology is allowing for deep sea observation, collection, and preservation.

An Overview

What is the deep sea and how deep is it actually?

It’s believed that the deepest part of the ocean is about 35,876 feet below the surface¹.

There are many layers to the ocean which can be divided into 5 different pelagic zone (s) based on depth below sea level: the Epipelagic (0-660 ft), Mesopelagic (660–3,300 ft), Bathypelagic (3,300–13,000 ft), Abyssopelagic (13,000–20,000 ft), and Hadalpelagic (20,000-36,000 ft) zone.

The deep sea is largely considered the part of the ocean without light and where continental shelves start to turn into continental slopes; light begins to fade at about 660 feet which is part of the Mesopelagic zone, also known as the twilight zone. This means that the majority of the ocean is considered the deep sea. We have learned the most from Alan Jamieson, a well-known marine biologist who has participated in over 65 deep sea expeditions and runs the Deep-Sea Podcast. Definitely check it out after reading this article if you want to learn more about these creatures.

Some Crazy Facts About Creatures Here

As of now, only about 20% of the ocean has been documented and understood. Even within that 20% are numerous microcolonies and ecosystems that have yet to be imagined. As marine science technology advances, scientists are finally able to get a glimpse into the world that exists at extreme depths.

One of the major factors preventing further research is pressure, which makes exploration and collection extremely difficult. As depth increases, temperature decreases while pressure increases.

Interestingly, the bottom of the ocean always remains just above slightly freezing at about 39° F. While this temperature may be adaptable for some creatures, the other extreme factors experienced in the ocean’s depths have caused many animals and bacteria to become highly specialized.

Light begins to dissipate after about 660 feet below sea level. Even in complete darkness, life found a way. Interestingly, many deep sea fish still have eyes. While it is still not fully understood why the deepest fish have eyes that would otherwise be used to sense visible light, it is strongly believed that they interpret bioluminescence instead.

Bioluminescence

Bioluminescence, or a chemical reaction between luciferin and oxygen that generates internal light, is a common method of both predation and protection in deep sea organisms. It is believed that up to 75% of deep sea organisms generate their own light.

For example, some species of anglerfish (Lophiiformes order) are able to light up their fishing lure appendage to attract prey in front of their large mouth. Other fish, like the marine hatchetfish (Sternoptychidae family), use bioluminescence for counter-illumination; this is a method of camouflage where the fish lights up the bottom of its body to better blend in with any light that is perceivable by a predator below.

Absence Of light

What happens to the organisms that depend on light, though? Photosynthetic organisms do not exist past the sunlight zone of the ocean. However, there are known species of coral and sponge that thrive outside of this layer.

Deep sea corals grow extremely slowly and are incredibly old as a result. Instead of using light for energy, these organisms rely on consuming other organisms. As we’ll see with other creatures, a lot of their nutrition is made up of organic material that falls from the ocean surface above.

Chemosynthesis

Even at the bottom of the ocean, life depends on bacteria. The nitrogen cycle looks a little different down here, though and organisms chemosynthesize instead³.

Chemosynthesis is the process that organisms use to create energy from other inorganic materials. For example, giant tube worms (Riftia pachyptila), contain symbiotic bacteria that use oxygen and hydrogen sulfide to provide the worm with essential nutrients.

Extreme Pressure

As ocean depth increases, pressure increases and conditions quickly become uninhabitable for most species. Most terrestrial and superficial marine organisms have gas-filled cavities, like lungs. Under high pressure, these cavities would collapse. As a result, deep sea species have had to evolve.

One of the ways organisms do this is by being comprised of mostly water. This way, internal pressure matches external pressure. Other ways of combatting extreme water pressure are by having flexible bodies, specialized lungs, slower movement, and reduced metabolic processes.

One instance of extreme adaptation to high pressure is the sperm whale (Physeter macrocephalus). These whales regularly exhibit vertical migration, sometimes spanning 1,000 feet. As you can imagine, pressure greatly varies across this distance. In response, sperm whales have collapsable ribs and lungs that can adjust as needed.

Collecting deep sea fishes becomes difficult for scientists due to these pressure gradients. Under these high pressures, the body works as intended with compacted functions. If the organism is brought to the surface, things are left to expand. So much so that, sadly, organs are sometimes forced out of the orifices of the animal, resulting in death.

New research and technology will hopefully allow deep sea fish and other specimens to be brought to the surface for continued observation. For now, scientists must rely on washed-up carcasses and real-time discovery on the sea floor.

Unique Ecosystems

While the ocean floor is a unique ecosystem in itself, there are self-sustaining environments with species found only in those locations. One of these ecosystems surrounds hydrothermal vents.

Hydrothermal vents are fissures in the deep ocean where seawater is cycled through the sediment and geothermically heated. The water is then released back into the ocean, filled with important minerals and gases. Hydrothermal vents are often located near areas with high volcanic activity.

Hydrothermal vents are rich in minerals and gases. If these factors don’t kill the organism, then the intense heat will sometimes reach 700° F. However, some deep sea organisms are found only in these ecosystems, such as the yeti crab (Kiwa spp.) and the scaly-foot gastropod (Chrysomallon squamiferum).

Another mini ecosystem that emerges in the deep ocean is known as whale fall. This is when a deceased whale falls to the ocean floor and becomes a temporary ecosystem, though sometimes lasting a few decades.

Whale falls are very important for local ecosystems as well as those towards the sea surface. Some common deep sea fish seen around whale falls are hagfish (Myxinidae family) and sleeper sharks (Somniosus spp.). Many other invertebrates and small crustaceans also make their homes in whale falls, like mussels, clams, and octopuses.

Top 15 Deep Sea Fish

While you might not know any deep sea fish off the top of your head, there are a few unmistakable species. Here are some of the most common deep sea species you may have only seen in pictures or may not be familiar with at all! We have a video below for you from our YouTube Channel. Check it out along with the blog post as the blog goes into more detail. Subscribe if you enjoy our content as we post videos every week!

1. Anglerfish

• Scientific Name: Lophiiformes order
• Diet: Carnivorous
• Size: Up to 3 feet; most individuals stay under 7 inches
• Origin: Worldwide
• Depths: Epipelagic to mesopelagic (<3,300 ft)
• Unique Features: Fishing rod predation

There are over 200 species of anglerfish. A select few of shallow water species are available in the aquarium hobby, such as species from the Antennarius genus.

Anglerfish are one of the most recognizable deep sea fish, but they can also live in shallower zones. Deep sea species are easily identifiable by the modified fin ray that dangles in front of their mouths and acts as bait for their prey. Most times, the bait on this fishing rod is bioluminescent.

Another interesting fact about anglerfish is that most species display high degrees of sexual dimorphism. For anglerfish, this means that the male is significantly smaller than the female. In some cases, the male becomes a parasite attached to the female purely for reproduction purposes.

2. Black Seadevil

• Scientific Name: Melanocetus spp.
• Diet: Carnivorous
• Size: 1-7 inches
• Origin: Atlantic, Pacific, and Indian Oceans
• Depths: Mesopelagic to bathypelagic (660–13,000 ft)
• Unique Features: Dark body coloration

One notable genus of anglerfish is the group of black seadevils (video source). These fish have pitch-black skin that allows them to blend in across the twilight zone and deeper.

Within this genus is one of the most recognizable species, the humpback anglerfish (Melanocetus johnsonii).

3. Viperfish

• Scientific Name: Chauliodus spp.
• Diet: Primarily carnivorous
• Size: 12 inches
• Origin: Atlantic, Pacific, and Indian Oceans
• Depths: Mesopelagic to bathypelagic (660–13,000 ft)
• Unique Features: Vertical migration; bioluminescent lure

At first glance, the viperfish is a very intimidating fish. These fish lack scales and seem to be almost transparent. They have large bottom teeth and an extendable jaw that can open large for bigger prey.

Like many other fish in the meso- and bathypelagic zones, viperfish display bioluminescence. To attract prey, viperfish have a modified bioluminescent fin ray they use to dangle in front of their mouths, similar to anglerfish. To hide from predators, viperfish can also counter-illumination to better blend into their surroundings.

Lastly, viperfish exhibit vertical migration, specifically diel vertical migration where they live in deep water during the day and move to shallower conditions at night. There, they hunt for shallow water fish and invertebrates. Due to their slow metabolism, these fish probably don’t need to migrate every night.

4. Sleeper Shark

• Scientific Name: Somniosidae family
• Diet: Carnivorous
• Size: 20+ feet; most individuals average 12 feet
• Origin: Arctic Ocean
• Depths: Mesopelagic to bathypelagic (660–13,000 ft)
• Unique Features: Anti-freeze proteins

The sleeper shark (video source) is one of the more well-known species of shark, namely the Greenland shark (Somniosus microcephalus) which has been known to live to 500 years. These sharks live in greater depths in polar and subpolar waters and have had to adapt to cold temperatures. They have done this by using an anti-freeze protein that prevents their blood from freezing.

It is believed that these cold conditions, in addition to their slow movement and metabolism, allow these sharks to live for such long times. Sleeper sharks may migrate during warm and cold seasons, but they regularly move across ocean zones between the day and night.

5. The Sarcastic Fringehead

• Scientific Name: Neoclinus blanchardi
• Diet: Carnivorous
• Size: 8 inches
• Origin: Pacific Ocean
• Depths: Epipelagic (0-660 ft)
• Unique Features: Large mouth

The sarcastic fringehead fish doesn’t come from the deepest parts of the ocean but still lives towards the edge of the epipelagic zone at an average depth of 300 feet.

These fish make the list due to their giant mouths that open up triangularly on the sides. While these large mouths may be used for prey, they’re largely used for competition between males battling for space and territory. These fish live in tight crevices in shallow waters and regularly need to defend their homes.

6. Stoplight Loosejaw

• Scientific Name: Malacosteus spp.
• Diet: Carnivorous
• Size: <1 foot
• Origin: Worldwide
• Depths: Mesopelagic to bathypelagic (660–13,000 ft)
• Unique Features: Open mouth; pharyngeal teeth; fang-like teeth; suborbital photophores

A light in the dark, the stoplight loosejaw has fearsome sharp teeth and a flashing red light. The stoplight loosejaw (video source) is aptly named for its hanging, bottomless lower jaw which gives way to many fang-like teeth and pharyngeal teeth. To help catch prey, these fish use red suborbital photophores that emit from their head to view prey; it is believed that many fish that live in low light conditions cannot see red light.

For being such a large fish with high evaluation traits, stoplight loosejaws prefer smaller foods, like copepods and crustaceans.

7. Chimaera

• Scientific Name: Chimaeriformes order
• Diet: Carnivorous
• Size: 5 feet
• Origin: All oceans besides the Antarctic
• Depths: Epipelagic to bathypelagic (<13,000 ft)
• Unique Features: Cartilagenous

Not to be confused with the mythological chimera, chimaeras (video source) are cartilaginous fish similar to sharks and rays. These are very large fish that have become accustomed to the pitch black, though some species of chimaera can be found in shallow and coastal waters.

Chimaeras have a unique way of swimming, which makes them appear as though they’re flying through the water. This is due to their large pectoral fins that can be used to gently push them along without much effort.

Like many other cartilaginous fish, chimaeras use electroreception to sense their prey in the water. They mainly eat crustaceans.

8. Mariana Snailfish

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• Scientific Name: Pseudoliparis swirei
• Diet: Carnivorous
• Size: <1 foot
• Origin: Pacific Ocean
• Depths: Hadalpelagic (20,000-36,000 ft)
• Unique Features: Transparent skin

One of, if not the deepest fish ever recorded, the Mariana snailfish is named after its home in the deep dark caverns of the Mariana Trench. This transparent fish is the top predator in some stretches of the trench, feasting on small crustaceans and other fish.

An interesting discovery about the Mariana snailfish is its adaptation to laying unusually large eggs, though the exact reason for this evolution is not known.

9. Lanternfish

• Scientific Name: Myctophidae family
• Diet: Carnivorous
• Size: <6 inches
• Origin: Worldwide
• Depths: Epipelagic to bathypelagic (<13,000 ft)
• Unique Features: Extremely prevalent; bioluminescence; vertical migration

Arguably the most prevalent deep fish in all the world’s oceans, the lanternfish is believed to make up about 65% biomass of all deep sea fish. This means that they’re an extremely important food source for their immediate ecosystem as well as those above and below, including birds and other land-dwelling marine animals. They were recorded on video for the first time in 2007 and reported by National Geographic.

Lanternfish are named after their prominent use of bioluminescence. These fish emit blue, green, or yellow light depending on species and sex. This is used to evade predators as counter-illumination.

These fish also display diel vertical migration, where they remain in and around the bathypelagic zone during the day and move to the epipelagic zone at night to avoid predation and feed on their favorite food, zooplankton.

10. Red Handfish

• Scientific Name: Thymichthys politus
• Diet: Carnivorous
• Size: 3 inches
• Origin: Tasmania
• Depths: Epipelagic (<660 feet)
• Unique Features: Red coloration; hand-like fins

The red handfish (video source) isn’t a true deep sea species, but their appearance is similar to that of anglerfish, minus the light. Red handfish are found in very exact reef ecosystems surrounding the country of Tasmania.

These fish have a very unique light red body speckled with darker red spots. They are especially recognizable by their hand-like fins that they use to scoot themselves across the sea floor to search for worms and other small crustaceans living in the sediment.

The red handfish is currently recognized as a critically endangered species.

11. Rattail Fish

• Scientific Name: Macrouridae family
• Diet: Carnivorous
• Size: 4-60 inches
• Origin: Worldwide
• Depths: Epipelagic to bathypelagic (<13,000 ft)
• Unique Features: Big head and slender tail

Also known as grenadiers, members of the family Macrouridae are very abundant in the deep ocean (video source); it is believed they make up 15% of the population. There are many different species of this fish, with some growing to massive sizes. Some species may also form schools.

These fish get their name from their large head, big eyes, and tapering tail that resembles that of a rat.

12. Faceless Cusk Eel

• Scientific Name: Typhlonus nasus
• Diet: Carnivorous
• Size: 11 inches
• Origin: Pacific and Indian Oceans
• Depths: Bathypelagic to abyssopelagic (3,300–20,000 ft)
• Unique Features: Reduced face; large nostrils

The faceless cusk eel (video source) has a very wide vertical range of distribution. Though ‘eel’ is in its name, cusk eels are not related to true Anguilliformes that live in shallow waters.

The faceless cusk eel is a relatively rare fish to find, though is unmistakable once seen. These fish have a large face, though often lack eyes. They have large nostrils that are sometimes mistaken as eyes. The mouth is at the very bottom of the face.

13. Deep-Sea Lizardfish

• Scientific Name: Bathysaurus ferox
• Diet: Carnivorous; sometimes cannibalistic
• Size: <28 inches
• Origin: Atlantic Ocean and Indo-Pacific (Indian ocean)
• Depths: Mesopelagic (660–3,300 ft)
• Unique Features: Upward-pointing mouth; sharp teeth

Fearsome-looking fish, deep-sea lizardfish are ambush predators (video source). They live on the sea floor waiting for other fish, including other lizardfish, to swim above. Then, they use their large, upward-pointing mouth lined with teeth to catch their prey.

14. Atlantic Wolffish

• Scientific Name: Anarhichas lupus
• Diet: Carnivorous
• Size: 5 feet
• Origin: West and east coasts of the Atlantic Ocean
• Depths: Epipelagic to mesopelagic (<3,300 ft)
• Unique Features: Antifreeze proteins; protruding teeth

The Atlantic wolffish is a very recognizable species and is often caught in bycatch. These are large fish that sometimes enter the twilight zone, where they prefer to stay hidden among the rocks and caves.

Atlantic wolffish have very large teeth and a strong bite that helps them regulate green crab and sea urchin populations. To help compensate for cooler water temperatures, wolffish have special anti-freeze proteins that stop their blood from crystallizing.

15. Barreleye

• Scientific Name: Opisthoproctus soleatus
• Diet: Carnivorous
• Size: 4-5 inches
• Origin: Eastern Atlantic Ocean, South China Sea
• Depths: Mesopelagic (1,600 – 2,300 ft)
• Unique Features: Tubuler eyes and transparent head

The barreleye (also known as the spook fish), is one of the strangest fish you will come across in the ocean. It has a transparent head and tubuler. The transparent head allows it to soak in more light. These features help them hunt zooplankton. The fish has no teeth, is spineless, and fairly small, only growing to 4 – 5 inches in length.

Conclusion

Marine life doesn’t just stop past the reach of light. The depths of the ocean are full of life, though a very different kind of life than what we’re used to. Animals have had to make special adaptations to these extreme environments, like bioluminescence and anti-freezing proteins in their blood. Some may also take on the amazing challenge of vertically migrating hundreds of feet every day for their own protection and for food.

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Mark Valderrama

I’m thrilled that you found Aquarium Store Depot! Here you’ll find information on fish, aquariums, and all things aquatics related. I’m a hobbyist (being doing this since I was 11) and here to help other hobbyists thrive with their aquariums! I adhere to a high quality Editorial Process and Review products with real life field usage and practical analysis.

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