Do fish need to drink water? How freshwater vs. saltwater fish process water.
Water is a big part of our lives. Whether we're swimming in it, washing ourselves off with it or drinking it, human beings need water to survive. The average U.S. adult drinks about 44 ounces of water per day, according to the Centers for Disease Control and Prevention. The human body itself is about 60% water.
Animals and plants, like humans, need water to survive. But what about the 3.5 trillion fish swimming around in the ocean, for whom water is their home? Do fish need to drink water like we do?
Do fish drink water?
Fish do consume water and need it to survive just as humans do. But fish don’t necessarily drink it as a human drinks a glass of water.
Fish consume water through a process known as osmosis. Merriam-Webster defines osmosis as “movement of a solvent (such as water) through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane.”
In simpler terms, osmosis is the process of something passing through a thin sheet to alter and balance a substance in something. Fish absorb water through gills through the process of osmosis, essentially being their equivalent to drinking water.
Do all fish drink water through osmosis?
Not all fish drink water solely through osmosis. According to McGill University, saltwater fish consume water not only through osmosis, but also purposefully drink water to have some go through the digestive tract. Water does end up going into freshwater fish’s mouths, but instead of swallowing it, the water is filtered out through the gills.
Why don’t freshwater fish swallow freshwater?
Unlike saltwater fish, freshwater fish do not need to consume water through their mouth to survive.
McGill University explains freshwater fish’s blood and bodily fluids are saltier than the water they swim in. “ishes’ bodies, just like ours, need a certain concentration of salt to function best," says McGill University. Swallowing freshwater could throw off the balance in a freshwater fish’s body.
Why do saltwater fish swallow saltwater?
Saltwater fish swallow water for the opposite reason freshwater expel it. McGill states saltwater fish need to swallow saltwater in order to get enough in their system.
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