Do fish need to drink?
The answer is yes and no - saltwater fish drink, freshwater fish do not. The reasons are all down to a matter of physics and a process knows as osmosis.
When two fluids of differing concentrations are separated by a membrane - in this case, the skin of the fish - water always flow towards the more highly concentrated solution. The body fluid of freshwater fish is more highly concentrated than the surrounding water. Therefore water is absorbed into the body through the skin and gills and the fish must actively excrete water, otherwise, it will eventually explode. The opposite is true for saltwater fish. In their case, the surrounding water is more highly concentrated and draws fluid out of the fish. This means the saltwater fish must actively take in water to avoid drying out. They take in water through their mouth, mucous membranes and gills. The salt is excreted by the gills before reaching the body.
The answer is yes and no - saltwater fish drink, freshwater fish do not. The reasons are all down to a matter of physics and a process knows as osmosis.
When two fluids of differing concentrations are separated by a membrane - in this case, the skin of the fish - water always flow towards the more highly concentrated solution. The body fluid of freshwater fish is more highly concentrated than the surrounding water. Therefore water is absorbed into the body through the skin and gills and the fish must actively excrete water, otherwise, it will eventually explode. The opposite is true for saltwater fish. In their case, the surrounding water is more highly concentrated and draws fluid out of the fish. This means the saltwater fish must actively take in water to avoid drying out. They take in water through their mouth, mucous membranes and gills. The salt is excreted by the gills before reaching the body.
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