You know how we breathe air and drink water, but filtered water, not salt water. Then there’s the saltwater fish, they breathe air, but they only drink salt water. For example, salmons, they’re anadromous, they are born in freshwater, then move to the ocean(salt water), then go back to freshwater to reproduce.
But how do saltwater fish live in salt water? Well, they use a process called, osmoregulation. Osmoregulation can let them control the amount of salt and water in their body, which is pretty cool if you ask me.
Saltwater fish drink a lot of water, then they have this extra salt in their body. Extra chloride ions are removed by active transport and leaves the body by their kidneys or gills. And since sodium ions are attracted to chloride ions, it follows it outside the body. And for saltwater fish, they have to drink a lot of water to get enough water for their system.
It’s the opposite case for freshwater fish. It’s pretty dangerous if they drink too much water, they either drink little or no water at all. They urinate huge amounts and it’s very watery. They gain their salt from the food they eat.
But for salmon, it’s different since they live in both fresh and salt water. When they’re in freshwater, they do what other fish do. Urinate a lot, and get salt from food. But when they’re in saltwater, they produce cortisol. These cortisol starts growing chloride cells. And these chloride cell ejects chloride, and when chloride ions are excreted, the salt follows.
In conclusion, osmoregulation is an important part of saltwater fish to have, without it, they wouldn’t be able to live. And I never really noticed how salmons are actually a pretty complicated fish.
I hope you enjoyed this essay, please comment if they’re any mistakes I should change. Thanks!