What Is The Most Intelligent Fish In The Sea?

What is the most intelligent fish?

Manta rays have the biggest brain of any fish swimming in the ocean. They are cartilaginous fish from the Mobula genus that can be found swooping around the ocean, covering vast distances as they forage for plankton. 

Their lifestyles require good navigational skills and senses, and they are able to synchronize their behaviors to optimize foraging, such as targeting humans’ artificial lights for moonlight feeds. The lights draw in more food, and manta rays have been using them to feed since the 1970s.

According to OCEANA, manta rays’ big brains are large even compared to their massive body size. They’re the biggest brains of any fish (including whale sharks, the largest fish in the ocean) and have highly developed areas associated with communication, problem-solving, and learning.  

Manta rays and the mirror test

Captive manta rays have been held up to the famous mirror test, in which animals are shown their reflection to see if they can recognize themselves. The 2016 study found what it described as the prerequisite to passing the mirror test as the manta rays didn’t try to socially interact with their reflection and showed “frequent unusual and repetitive movements in front of the mirror suggested contingency checking [which is when an animal moves to test if its reflection moves]”.

Those behaviors included rolling and unrolling the fins by their mouths – something they would never normally get to see – and blowing bubbles while looking at the mirror. A delightful image, but the researchers noted that a mark test is needed to confirm if this constitutes self-awareness. Another hopeful candidate for passing the mirror test is the cleaner fish, as scientists have observed how it would scrape off a parasite tattoo if it saw itself in the mirror.

How do we measure animal intelligence?

Manta rays may well have the biggest brains of any fish in the ocean, but we can’t assume that correlates directly to intelligence. Just look at the “bird brain” avians. We used to think their tiny brains meant they were very stupid, but we now know that composition can be more important than size, and that many birds exhibit high levels of intelligence (some even like dipping their food in condiments).

Investigating animal intelligence raises a sticky issue: how do we measure it? A human who’s good at poker demonstrates a kind of intelligence that’s useless to a fish, so we can’t call a fish stupid for lacking a skill that serves it no benefit at all.

 “I think many researchers understand that ‘intelligence’ is a difficult concept to define and even more difficult to test ‘fairly’,” said Dr Alecia Carter of University College London, an expert in animal behavior, to IFLScience. “There is such a fraught history with even making tests within one species (humans) that I don’t think it’s helpful to say that, e.g., chimpanzees are more intelligent than gorillas (or sunfish, or Komodo dragons, etc.). Intelligent in what way?”

“Meerkats and lizards and baboons have to navigate their worlds. But, for the most part, it doesn’t matter that they have different intelligences. They’re intelligent enough in different respects to survive and, hopefully, thrive in the world, which is what matters. We focus a lot on the kinds of intelligence that we value, but animals have some pretty impressive intelligences that we don’t have access to at all.” 

We’ve yet to crack if animals have “language,” but it was recently observed that humpback whale song exhibits some of the crucial laws of human language. Could it be that they’re spinning sonnets we just can’t understand? We might one day find out, as scientists are trying to find a way to talk to whales, and we did already have one conversation with them (even if nobody knew what was being said).

And speaking of animals overlooked for their smarts, what is the most intelligent snake species?