I recently came across the following quote on the twitters, attributed to Albert Einstein:
Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.
I doubt that it's a genuine quote, but is the implied claim that all fish are incapable of climbing trees true?
Related question: Did Einstein say the "if you judge a fish" quote that many are attributing to him?
There are several fish which are capable of achieving this:
Mangrove killifish
The mangrove killifish (Rivulus marmoratus), found among the mangroves in Florida, Latin American and Caribbean, is a strange fish indeed. For starters, this is the only vertebrate animal that is known to fertilize its own eggs. There are males and females, but most of these little fish are hermaphrodites.Mangrove killifish are able to alter their gills to be able to live out of the water. When the water around the mangroves dries up, these fish climb up into the trees and hide in logs until the water returns. Once it's safe, they change their gills back and venture back to the water.
Climbing Gourami
Shirlie from Freshwater Aquariums told me about these fish when I was excitedly telling her about the mangrove killifish. I've always been a fan of the beautiful gouramis in my own aquarium, but I never knew that any of them could climb. They hail from Africa and Southern Asia.One is called a climbing perch (Anabas testudineus). If the water it lives in dries out, it will climb out and travel in search of a new home. Its gills are spiny, and the climbing perch can use them (as well as its anal fin) to even climb up trees.
Climbing Catfish
Finally, scientists have discovered Lithogenes wahari recently. This member of the catfish family can actually grasp with its pelvic fin. They have been finding specimens clinging to rocks, but it's not a stretch to think that they could climb trees too. This fish also has a sort of bony armor that protects its head and tail.
From the Science Centric regarding the climbing catfish:
the bony armour that protects its head and tail, and a grasping pelvic fin that allows it to climb vertical surfaces.
It's definitely true that some fish can climb trees. It's certain that they don't do it very often.
What a ridiculous question! Of course not!... Oh, wait... Errr.
Yes
There are more than one fish that can climb trees. [Reference: Quantum Biologist, which is "only" a blog, I dug further.]
One example that the Quantum Biologist describes is the Mangrove Rivulus.
They lose their aggressive habits, climb the nearest tree or rotting log, and stuff themselves into the cracks and insect-bored holes. Their physiology changes: instead of breathing through their gills, they breathe (and excrete waste) through their skin. They can stay that way, a literal fish out of water, for over two months, just waiting in the trees for rain to come.
Source: Quantum Biologist
I found several sources (including Reuters) that confirmed it could live outside of the water, inside damp logs and crab burrows for long periods during dry spells, but I couldn't find any that use the word "climb". The Florida Museum of Natural History use the term "slithering and flipping" in its search for a place to hide.
There's a YouTube video showing the fish inside a log, but the quality is very poor, and hardly proof of anything.
The US Department of Commerce has declared it a Species of Concern.
