4 Dumbest Fish

Written by Abdulmumin Akinde
Updated: January 24, 2023
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Fish are some of the world’s most unique and diverse aquatic species. Their uniqueness is demonstrated by the diversity of their habits, appearance, diet, and habitats. Fishes live on continental shelves and within diversified coral reefs. They are thought to be among the smartest animals in the world, with a level of intelligence that supersede those of many higher vertebrates. While many fish have demonstrated remarkable intelligence over time, not all fall into that category. Like many of the other dumb animal species, some fish are quite dumb, and this article lists some of the dumbest fish species on the planet. 

Ocean Sunfish (Mola Mola)

Ocean sunfish or Mola mola have small mouths and large eyes on their massive heads.

Ocean sunfish or mola mola have small mouths and large eyes on their massive heads.

©Anna K Mueller/Shutterstock.com

Also known as the mola mola, this gigantic flat bony fish does a very poor job at being a fish. Unlike other fish that are active swimmers, the sunfish simply floats through the ocean like a giant blob because it cannot use its fins to propel itself. 

Despite being sizeably large, the sunfish has no feature to protect itself and cannot effectively prey on smaller fish. Despite the monstrous look of this giant fish, the ocean sunfish is practically useless as a predator. They can only feed on jellyfish, another brainless ocean dweller that is slow enough for them to catch up with. The only reason why the sunfish have survived for so long is that they’re prolific breeders. They produce more than any other fish – up to 300 million at a time. 

Most of these don’t reach adulthood because they’re at the mercy of oceanic predators. When this fish comes in contact with the overlords of the ocean, life or death depends on whether the attacker is filled up with food or hungry. 

The ocean sunfish is so dumb and slow that its body is often covered with parasites and even more parasites on top of the original one. When they surface in the sun, seabirds often peck off those parasites on their body. They move at the rate of about 2 miles per hour. Most swimming humans would top that speed easily. The sunfish weighs between 545-4,409 lb, but its brain is about 0.17 oz, making it one of the dumbest fish in the world.

Goblin Shark

goblin shark in ocean

The goblin shark looks scary, given its size of over 12 feet.


Generally, the word ‘shark’ is an automatic fear trigger. Sharks are widely believed to be one of the most brutal fish species because of their deadly instincts. Sharks are also known to have retentive memories and can display complex behaviors with a good grasp of their immediate surroundings. However, one species of shark that probably didn’t get the memo on all these features is the goblin shark.

The goblin shark is a deep-sea species typically found in the dark and icy oceans like the Pacific, Atlantic, and Indian oceans. They live at the bottom of the oceans along continental shelves and can grow up to 12 feet long with a weight of 460 lb. This shark is slow, sluggish, and lazy compared to other sharks due to its flabby body and short fins. The shark has a distinctively long and flat snout which gives them a rather unattractive appearance (call it a dumb look if you must). 

The goblin shark is not a fast swimmer like other sharks. In fact, they’re bad swimmers and are practically blind, with a lack of speed and agility. They rarely actively hunt, waiting instead for prey to find them. A lot of information on the goblin shark remains a mystery since they are hard to study. 


moon jellyfish

Jellyfish are not fish, but are certainly not the most intelligent of animals


Technically, jellyfish aren’t fish. They are invertebrates so varied in appearance that scientists generally refer to them as gelatinous zooplankton. They are not viewed as actual fish due to their interesting anatomy. However, they deserve a spot on this list of dumbest fish species due to how rudimentary their “brains” are (or their complete lack of one).

Many scientists consider this unique group of organisms as living fossils. Jellyfish have existed for over six hundred million years in the warm waters of the ocean. Quite a remarkable achievement for an animal with no brains at all. The umbrella-shaped ball of cells relies on sensory organs at the base of their tentacles to feel their surroundings and detect various kinds of stimuli, salinity, and temperature in the ocean. 

Jellyfish are composed of 98% water and have no brains, which means they are incapable of thinking and practically dumb. Their nervous system comprises a neural net that operates with very few and simple reflexes like swimming and eating. The simplistic design of the jellyfish means it is incapable of learning. When they wash ashore, their bodies often vanish within a few hours.

Bony-Eared Assfish

Bony Eared Assfish

©R. Mintern / public domain – License

The bony-eared assfish is a cusk-eel species that lives deep within the ocean. While some attributes that condemn it to this category are quite natural, they have also made the species vulnerable. There are many dumb things about this fish species, and their name is just one of them. One would almost mistake an assfish for a tadpole, because that’s what they really look like. 

The fish has no bone mass, possesses the smallest brain-to-body ratio of all vertebrates, and lives within a part of the sea where food is substantially scarce. Its lack of a brain means it has no proper thinking elements to engineer true survival traits.

They’re largely solitary, living deep down in deep tropical oceans. Staying hidden like this is the only thing that keeps this fish from getting caught in fishing nets or getting eaten by predators. Scientists still know very little about this creature, but it is obvious they’re not the smartest fish in the ocean. 


It’s difficult to say what truly constitutes fish intelligence since being smart is a very subjective observation. However, the fish listed here are among the dumbest fish species in the ocean because they lack many of the expected qualities one would expect them to have to survive in such a brutal environment like the deep oceans where they live. 

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The photo featured at the top of this post is © Peter Halasz / CC BY-SA 3.0 – License / Original

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About the Author

Abdulmumin is a pharmacist and a top-rated content writer who can pretty much write on anything that can be researched on the internet. However, he particularly enjoys writing about animals, nature, and health. He loves animals, especially horses, and would love to have one someday.

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  1. Scholarly, Available here: https://bscholarly.com/dumbest-animals-in-the-world/
  2. Awesome Ocean, Available here: http://awesomeocean.com/trending-now/weirdest-shark-species/