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.

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.

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.

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).

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.

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”.

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.
