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Monsters or masters of the deep sea? Why the deepest deep-sea fish aren’t as scary as you might think


How deep can fish live in the ocean? That question has occupied my mind for more than ten years. But my research team’s discovery of the deepest sea fish, announced this week, may not be the definitive answer. There may be more. How deep – and how strange – remains open to debate.

Last year my colleagues and I went on an expedition to the deep trenches around Japan. Having found the Mariana snailfish back in 2014 — believed to be the deepest on record — we suspected that with more research and a better understanding of things like temperature, Japan’s trenches would house a fish at even greater depths.

After another 63 deployments of our deep sea cameras, bringing our total to about 250 around the world, we hit the jackpot.

We found a likely new species of fish in the Izu-Ogasawara Trench and filmed it many times at depths between 6,500 and 8,000 meters. Then, at a staggering 8,336 meters, a rather unassuming little juvenile slowly swam past the camera, oblivious to the fact that it had just become the camera. deepest fish ever recorded.

Researchers near Japan capture images of the deepest fish ever recorded underwater (The Guardian)

Read more: Ten things you never knew about the ocean’s deepest places

Much more than monsters

If you ask anyone what the deepest fish in the world looks like, they’ll likely conjure up an image of a scaly, black, nondescript creature with bioluminescent lures, large fangs, spiky fins, and demonic eyes lurking in the depths and waiting to attack unsuspecting people. victims. It would be nothing like the shallow water fish we eat, keep as pets or pay to see in aquariums. It would be more the stuff of nightmares.

While these types of visually striking creatures exist, they are often not that deep or that big. Axfish, fangs, lanternfish, dragonfish, viperfish and anglerfish live in the midwaters of the twilight zone (less than 1000 m deep). Many of these classically spooky monsters are actually very small, simply magnified in our imaginations, lacking any sense of physical scale.

Sloane’s Viperfish is one of the most recognizable deep-sea fish with its long fang-like teeth.
Diego Grandi/Shutterstock

The black body, large eyes, bioluminescent lures, and unfamiliar fins and textures are all adaptations to a stealthy but efficient low-light life.

At deeper levels, where low-light adjustments are no longer necessary (because there is a total absence of light), marine life takes on other, less dramatic forms. Adaptations to depth, or rather high pressure, are usually not things we can see, but rather changes at the level of cells or body tissues to allow for life at depth.

For example, if we take the deepest fish, the deepest shrimpthe deepest jellyfishthe deepest anemone and the deepest octopuswe find them at depths of 8,336m, 7,703m, 10,000m, 10,900m, and 7,000m respectively (between 4.3 and 6.8 miles deep).

The deepest of the deep

The deepest fish in the world isn’t really a deep-sea fish. They are snailfish in the ray-finned fish family called Liparidae. There are over 400 species of snailfish, and most of them can be found in shallow waters, or even estuaries in some cases. This family of fish has adapted to a range of different environments and habitats, including the deepest.

We found the deepest of them all in the Izu-Ogasawara Trench at 8,336m, but this fish falls short of any preconceived visual impression of what its deepest dweller should look like. They are, in fact, tiny, translucent pink, wayward fish that swim like tadpoles and wouldn’t look out of place in a sunlit lagoon.

Two deep-sea snailfish, like pink tadpoles, resting on a dark gray background
These two specimens are the deepest fish ever caught, recovered from a depth of 8,022 meters in Japan’s trench.
Alan Jamieson, Author provided

Likewise, if we look at the deepest of the large crustaceans, which happen to be penaeid shrimp (benthesicymus), there is nothing so unfamiliar about them. They can be up to a foot long, strikingly red in color, and swim and behave exactly as a shrimp would be expected to swim and behave in our coastal regions. He wouldn’t look out of place at the local fish market.

Read more: Deep-sea reefs are spectacular and barely explored – they need to be preserved

The deepest jellyfish looks like a normal jellyfish. The deepest anemones are attached to rocks at the bottom of the Challenger Deep, the deepest place on Earth. These still unknown species are attached to rocks that filter food from the water. They look more plant-like and resemble delicate and beautiful flowers swaying in the wind.

Two deep sea images of the white anemone resembling delicate and beautiful flowers swaying in the wind
Like delicate flowers from an underwater garden in the deepest place on earth, the deepest anemones.
Caladan Oceanic, Author provided

And then there’s the octopus, an animal that has haunted sailors for centuries. In contrast, the newly discovered species Dumbo octopus (Grimpoteuthis) is a small and cute little cephalopod with fins that resemble big ears (as in Dumbo the elephant). The species was filmed nearly 2,000 meters deeper than any other octopus or squid at a depth of nearly 7,000 meters.

A Guide to the Dumbo Octopus, from Deep Marine Scenes.

The true masters

Essentially, dark sea creatures in the upper ocean detract from the true deep sea creatures, giving us a false impression of the natural aesthetic of this community.

While the dark sea creatures have adapted to low light in a way that tickles our imagination, the real deep sea creatures represent more of a case of where the wild things aren’t.

The snailfish are the true masters of the deep, not monsters of the deep. If we ever really want to understand and appreciate the ocean as the greatest habitat on Earth, we need to retrain our brains and realize that even thousands of feet underwater, there are populations of tiny fish just going about their daily business.

A still image from deep-sea video footage showing an octopus, snailfish, and a shrimp.
Come eat, an octopus, two eels and a shrimp approach one of the deep-sea cameras.
Caladan Oceanic, Author provided

Read more: The ocean is not a quiet place

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