Ten Amazing Fish Facts

Esther’s writing prompt: November 12 : Fish

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This is not a super fact but a collection of interesting facts about Fish. They are not very important facts but amazing facts.

Freshwater fish Riffle minnow (Alburnoides bipunctatus) underwater photography. Minnow in clean water and nature habitat. Natural light. Lake and river habitat. Wild animal. Underwater photo of fish. | Ten Amazing Fish Facts
Minnows Asset id: 1182854671 by Rostislav Stefanek

Most Fresh Water Fish would die from dehydration if put in Sea Water

Most freshwater fish would die from dehydration if placed in seawater due to a process called osmosis. The same is true for saltwater fish placed in freshwater.  There are a few exceptions. So called euryhaline species are able to more or less handle both freshwater and seawater, an example is salmon. It is also why freshwater fish native to oceanic islands like Hawaii are euryhaline species. Freshwater fish that are not euryhaline species cannot travel to oceanic islands.

What is a Fish?

A fish is a vertebra (has a backbone and a brain protected by a braincase) that is aquatic, lives in water, has gills, fins, scales and is cold blooded. Dolphins, whales, jellyfish, and starfish are not fish.

Some fish have both gills and lungs

Lungfish have both gills and lungs. Their unique respiratory system allows them to breathe underwater with their gills and also breathe air from the surface with their lungs. Some species of lung fish can survive on land for several months.

Lung fish resting close to the bottom of the sea. The exact species is Neoceratodus forsteri (Australian lungfish).
Queensland lungfish, Mitch Ames, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons

Fish Can Be Raining from the Sky

Tornadoes over water have sometimes picked up both water and fish causing fish to rain down over land.

The illustration depicts a tornado / waterspout over land with lots of orange fish raining down.
Fish raining from the sky. Picture generated with the help of ChatGPT

Mudskippers the land dwelling fish

Mudskippers are fish that spend most of their time on land. It can walk on land, jump, and climb trees, by using their strong pectoral fins like legs and their tails as a lever. They breathe air through their skin and gill chambers. Below is a four minute video featuring mudskippers.

Fish the First Vertebra on Earth

Fish appeared more than 500 million years ago during the Cambrian period. They are believed to be the first vertebrates on Earth. They lay the foundation for the diverse array of vertebrate life that has since populated the planet’s ecosystems.

Some Fish can make Light

Anglerfish are deep sea fish that produce their own light using bacteria. The dangling glowing light attracts prey. Some species of angler fish live only 200 meters down in the sea while other species live as far down as 3,300 meters (11,000 feet).

Angler fish on background realistic illustration isolate. Scary deep-sea fish predator. Deep sea fish monster. | Ten Amazing Fish Facts
Angler fish on background realistic illustration isolate. Scary deep-sea fish predator. Deep sea fish monster. Asset id: 2134226987 by Konstantin G

Some Fish know how to use Tools

Wrasse are fish that use rocks as anvils to crack shells. They grab hard-shelled prey like crabs and mollusks, swim to a rock or coral, and repeatedly strike the prey against the hard surface to break it open. This is a form of  tool use.

This Wrasse is a long blue and orange fish.
Cuckoo wrasse. Olivier Dugornay, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0&gt;, via Wikimedia Commons.

Megalodon

The largest fish that has ever lived is likely the extinct shark Megalodon, estimated to have reached lengths of up to 70 feet and weighing 50-70 tons. The Megalodon was a giant shark believed to have gone extinct 2.6 million years ago, just in time for the appearance of our ancestors Australopithecus and Homo Habilis. They made a horror movie about a Megalodon that survived until modern times. It is called “The Meg”.

Megalodon shark with its mouth wide open pursuing two whales much smaller than it.
Artistic impression of a megalodon pursuing two Eobalaenoptera whales. Karen Carr, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0&gt;, via Wikimedia Commons.

Surströmming (Fermented Baltic Herring) a North Swedish Delicatessen

In 1987 I was selected by my University, Uppsala University in Sweden, to be part of a university level exchange student program. The exchange program was between Uppsala University and Case Western Reserve University in Cleveland, Ohio. In total we were six Swedes (two from Uppsala). I was studying Engineering Physics in Sweden. In the US, I would continue studying Electrical Engineering because the Swedish Engineering Physics program was very similar to the Electrical Engineering program at CWRU. One day we invited the other students to a Surströmming party. When we opened the cans, the American students headed for the windows and opened them. I should say there were other things to eat.

The fermented herring Surströmming from Sweden is often considered as one of the most unappetizing foods in the world. Just ask Google AI or ChatGPT this question, “what is the most unappetizing food in the world”, and you’ll see. The three top unappetizing food according to ChatGPT are Hákarl (Fermented Greenland Shark) – Iceland, Surströmming (Fermented Baltic Herring) – Sweden, and Casu Marzu (Maggot Cheese) – Sardinia.

I grew up with this food, and I don’t think it is unappetizing. It might not be beef bourguignon or trout almondine, but it isn’t bad. The problem is that the smell of Surströmming is not very pleasant and it is strong. However, it tastes quite different from the smell. It tastes like pickled herring with the addition of something sour like lemon. The taste is much better than the smell, which is why you should open the cans outside and then bring them in once the smell has settled. We did not do that because our party was partially a prank. Well, if you don’t like pickled herring, then you won’t like this either.

Ten Amazing Fish Facts
Four Swedes inviting Americans to a fermented herring party. Fermented herring is a north Swedish specialty. Unfortunately, all the Americans experienced a culture shock from the fermented herring. I am the guy smelling the fermented herring can.
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Author: thomasstigwikman

My name is Thomas Wikman. I am a software/robotics engineer with a background in physics. I am currently retired. I took early retirement. I am a dog lover, and especially a Leonberger lover, a home brewer, craft beer enthusiast, I’m learning French, and I am an avid reader. I live in Dallas, Texas, but I am originally from Sweden. I am married to Claudia, and we have three children. I have two blogs. The first feature the crazy adventures of our Leonberger Le Bronco von der Löwenhöhle as well as information on Leonbergers. The second blog, superfactful, feature information and facts I think are very interesting. With this blog I would like to create a list of facts that are accepted as true among the experts of the field and yet disputed amongst the public or highly surprising. These facts are special and in lieu of a better word I call them super-facts.

58 thoughts on “Ten Amazing Fish Facts”

  5. Charlee: “I would totally eat an entire can of that pickled herring.”
    Chaplin: “Me too.”
    Oona: “Oona has another fish fact! If you pull the temperature probe out of an aquarium and leave it dangling out in the room, the temperature in the tank will just go up and up and up and you can make yourself a giant batch of fish soup. Delicious!”

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  7. Interesting. In a couple of weeks I’ll be posting about freshwater trout in Armenia that were introduced in a saline lake in Kyrgyzstan. They not only survived but thrived. It’s only a small part of a larger post. Maggie

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    1. That is great Maggie. I am looking forward to your post. I can add that euryhaline species includes trout, salmon, bull sharks and round goby, but most other fish cannot adapt between fresh water and salt water.

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  8. Your post feels like a delightful stroll through the hidden corners of the aquatic world—playful, curious, and wonderfully informative. I love how you blend science with storytelling, turning each fact into a small spark of wonder. Even the Surströmming anecdote adds a charming human touch that makes the whole piece feel both educational and joyfully personal.

    One thought that surfaced for me while reading your collection is how fish often act as silent markers of Earth’s changing environments. From euryhaline species adapting across salty boundaries to deep-sea creatures thriving under immense pressure, their resilience quietly maps the planet’s shifts better than we realize. It feels like a natural extension of your intention—reminding us that every quirky fish fact is also a glimpse into the story of our world evolving in real time.

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    1. Wow, you certainly write eloquent and very kind comments. Thank you so much Livora and I believe your observation is is spot on. I love what you said — “fish often act as silent markers of Earth’s changing environments. From euryhaline species adapting across salty boundaries to deep-sea creatures thriving under immense pressure”

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  9. What a fascinating collection of fish facts! 🐟
    I really enjoyed how each section introduced something surprising — from freshwater fish dehydrating in seawater to mudskippers climbing trees, and even fish raining from the sky! Your explanations were clear, fun, and full of curiosity-sparking details.

    The Surströmming story at the end was the perfect personal touch — I could almost imagine the scene with the Americans running to open the windows! 😄 Cultural food experiences really do make the best memories.

    Thanks for putting together such an engaging and informative post. Learned a lot and had a great time reading it!

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  12. “This is such an amazing collection of fish facts! I love how you’ve highlighted not just the biology, but the quirky and fascinating behaviors of fish—from lungfish breathing air to mudskippers walking on land and wrasses using tools. The historical and scientific insights, along with the fun facts like fish raining from the sky, make this post both educational and entertaining. Truly inspiring and a wonderful read for anyone curious about marine life!”

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    1. OK 1. Most freshwater fish die in seawater but some can do both (salmon, trout). 2. What is a fish? 3. Some fish has both gills and lungs. 4. Waterspouts/Tornadoes can make it rain fish. 5. Mudskipper is fish that spends most of their time on land, breath air, and can climb trees. 6. Fish was the first vertebra. 7. Some fish can make light. 8. Some fish know how to use tools. 9. Megalodon an exctinct shark was 70 feet long. 10. Surströmming is a very smelly fermented herring. We had a Surströmming party in the dorm.

      Thomas

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  22. I liked “The Meg I & II” even though the idea is fantastical. I used to have a lovely aquarium that I loved to watch. Fish are so calming. And I remember going out on the lake and fishing with my father and grandfather. We always had great fish frys.

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    1. Those are great memories both that you liked the movies and fishing with your dad and grandfather, and the aquariums too. When I was a kid I did a lot of fishing with my father and grandfather too. My paternal grandfather was a very proud expert fisherman. However, one time when he was teaching my brother and I how to through out a lure with a fishing pole the hook got stuck in his pants and we could not get it off. So when we walked back home, through the village, he told us to walk closely right behind him so people wouldn’t see the lure hanging from his pants. He did not want his reputation as an expert fisherman tarnished.

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