Spotlight The Blobfish: The World's Ugliest Fish?

An article on the unusual blobfish found at extreme depths in the ocean. Probably not a fish for your reef tank, but interesting nonetheless.
  1. The blobfish, Psychrolutes marcidus, belongs to the same genus as the more familiar blob sculpin Psychrolutes phrictus in the family Psychrolutidae.

    Blobfish are deep-sea fish that live off the coasts of Australia, Tasmania, and New Zealand in the Pacific Ocean. They get their name because they literally look like blobs when taken out of their habitat. The scowling, almost-human face and the flabby look is usually how they look when disfigured because of the extreme change in pressure that the fish experiences out of the sea when it is brought up to the surface from the deep.

    The fish have large heads that take up a third of their body size. Their bodies taper so that they look like tadpoles.

    A blobfish, Psychrolutes microporos, out of water. Note the isopod on the lip.
    This photo is used with permission from the Australian Museum. The photo was taken by Kerryn Parkinson, NorFanz expedition, CSIRO. ©2019, All Rights Reserved.

    Looking at their best at home

    Blobfish live in depths ranging from 2000 to 4000 feet below sea level. This is the twilight zone where even submarines do not dive. Here, the pressure is about eighty times more than at sea level and the temperatures are low, usually between two and four degrees Celsius.

    Their bodies have developed several adaptations that help them survive these conditions. Scientists theorize that at those depths, the blobfish look more like their cousins, the blob sculpins because the high pressure is what helps them maintain their shape.

    Out of water, they expand into blobs with their faces wearing the miserable, human-like expression that has seen them win the prize for the world’s ugliest animal.

    How blobfish withstand the pressure

    Blobfish have evolved very soft bones because they would not withstand the high pressure with hard bones. The fish also lack teeth to avoid hard structures in their bodies. Their bodies are soft, mushy masses and they hardly have any muscle tissue.

    These fish do not have the swim bladders that help provide buoyancy in most fish. At those depths, the pressure would rupture the swim bladder and kill the fish. To stay afloat, the blobfish have evolved their bodies into a gelatinous mass of flesh that is slightly less dense than water allowing them to float around near the bottom of the sea without spending energy. These fish do not swim; they hover around the same spot or drift along with the current.

    Because of their unique bodies, it is almost impossible to keep them as pets unless you can recreate their natural habitat as much as possible. This means deep tanks.

    However, there is hope. As of 2017, the Fukushima Aquarium has kept a blob sculpin, Psychrolutes phrictus a member of the Psychrolutes family. This fish, aptly named Bob, was accidentally caught at a depth of below 2400 feet and has survived in the aquarium thanks to special customizations such as low light to mimic his natural habitat. In captivity, the fish has changed with its skin taking on a spiky look. In their natural habitat, both blobfish and blob sculpins have smooth skin with no scales.

    Psychrolutes marcidus.
    This image is in the public domain in its country of origin (US) and other countries and areas where the copyright term is the author's life plus 70 years or less.*

    So how do they feed?

    Blobfish have low metabolic rates because they have very little muscle. They do not pounce on their prey, they catch food by sucking in water then feeding on whatever comes in. They swallow food whole then their stomachs break down the food and absorb nutrients. Blobfish are bottom feeders, helping to keep the populations of crustaceans, sea urchins, and shellfish in check.

    Their inability to swim would be costly in depths less than 800 feet. However, this adaptation is useful in the very deep ocean and means the fish use up little energy and that explains their lazy lifestyle on the ocean floor. Most formidable predators cannot survive the extreme pressures at these depths. Besides, these fish have toxic acidic skin that makes them unpalatable.


    Mature blobfish grow to about one foot in size. They can enjoy long lives up to 130 years partly thanks to their low energy lifestyle, which also means slower growth.

    Female blobfish reproduce by laying thousands of pink eggs on the sea floor. They sit on these eggs until they hatch to protect them from other fish. Some fish have been observed to take care of their eggs communally to protect them from scavengers. Of all the eggs females laid, very few hatch and live on to maturity.

    Blobfish could be endangered

    Despite winning contests no one would envy and having no value as food or pets, blobfish are facing existential threats in the form of deep-sea trawlers. They are often caught as bycatch and die almost as soon as they reach the surface because of change in pressure, so it is not much help trying to save them by immediately throwing them back into the water.

    Scientists have long been concerned about the harmful effects of bottom trawling but have little success creating workable plans about how best to regulate bottom trawling in the high seas off Australia and New Zealand.

    Their small habitat and slow reproduction means blobfish are not capable of replenishing their population when their population takes a hit.

    On the other hand, they live in habitats hard for scientists to study. So, much about them remains unknown.


    *Alan Riverstone McCulloch (1885-1925) - Fisheries : Zoological results of the fishing experiments carried out by F.I.S. "Endeavor" 1909-10 under H.C. Dannevig. See Plate LV, Fig. 2, p. 440 in the pdf source (+page 215)


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    Author Profile: David Kimutai

    David loves visiting the ocean, and his favorite saltwater aquarium fish is the dwarf angel, genus Centropyge in the family, Pomacanthidae. He is a freelance science writer and digital marketer living in Nairobi, Kenya.

    His love for aquariums started when he was young, when together with his brothers, they fished a trout from a local stream and kept it alive at home for days before releasing it.

    His forum name is Davidangelfish

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