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Some fish species can live in both freshwater and saltwater. These species are called euryhaline fish. However, most fish species can only survive in one or the other based on their salinity tolerance, or how much salt their bodies can handle. The highly adaptable euryhaline species are able to endure a wide range of salt levels , according to The National Biological Information Infrastructure (NBII). They are successfully able to migrate back and forth between saltwater, such as the ocean, and freshwater, which includes certain rivers. There are two main types of euryhaline fish: anadromous and catadromous. Anadromous fish are born in freshwater but spend most of their lives in the sea, only returning to freshwater in order to spawn. These fish include salmon, smelt, shad, striped bass, and sturgeon, according to the Alaska Department of Fish and Game. Catadromous fish, on the other hand, generally live in freshwater bodies of water and only enter saltwater to spawn. North American eels and European eels fall under this category, according to the National Marine Fisheries Service (NMFS). Most fish that can only tolerate narrow ranges of salinity and are highly sensitive to any changes in the levels of salt to the water in which they dwell. These fish are known as stenohaline species and include goldfish, which can live only in a freshwater environment. Reversely, tuna can exist exclusively in saltwater, according to the NMFS. In fact, freshwater fish will often be unable to survive if the salinity levels of their surrounding water reaches more than .05 percent, according to the National Biological Information Infrastructure (NBII). When migrating, even euryhaline fish need to undergo an acclimation period, or time for their bodies to adjust to a different salinity than they are used to. By associating various habitats' salinity with different stages of life, euryhaline fish are able to balance salt concentrations between their bodies and their surrounding, according to NBII. Originally published on Live Science. Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.
On the other hand, freshwater fish can't survive in the ocean or saltwater because the seawater is too salty for them. The water inside their bodies would flow out their cells, and they wiil die of dehydration. Both processes are called Osmosis. But how exactly this process happens and why? What is Osmosis?A semipermeable membrane is a barrier that has small holes big enough to let liquid molecules enter, but small enough to block the flow of salt, sugar or other concentrated content. The membrane of a cell is semipermeable which means it blocks larger molecules and lets smaller molecules (like water molecules) pass through. For example, if you try submerging a raisin in fresh water, it will swell up; this is because the raisin has higher sugar concentration than the freshwater and water will keep flowing in. But, if you put a raisin in supersaturated salt water, the raisin shrinks even more because the water flows out. The supersaturated salt water has higher content concentration than the raisin. Osmotic Pressure and TonicityTonicity is the measure of osmotic pressure. There are three classifications of tonicity that you should know to understand better why fishes only survive in specific bodies of water. The three classifications of tonicity are:
What are Hypertonic, Hypotonic, and IsotonicHypertonicity is caused by a higher content concentration outside the cell than inside of it, and this results in the cell shrinking because water flows out of the cell to dilute the content outside. Hypotonicity, on the other hand, is caused by the high content concentration inside the cell, making the cell bloat and burst because water keeps flowing in to dilute the cell's solution. Isotonicity is the balance of solute concentration inside and outside the cell. There is no change in cell volume and no movement of water between the membrane. One example for isotonicity is red blood cells in plasma solution. Do fishes drink water? Do fishes pee?Yes! Due to osmosis, fishes need to osmoregulate, the process of maintaining a right amount of water in their bodies. Some fishes need to drink water, but all have to urinate frequently. Freshwater fish and saltwater fish survive according to how much salinity their body can sustain. Seawater is hypertonic to the fishes living in the ocean, which means that water is continually being sucked out of their bodies. To survive, saltwater fishes continually drink lots of water to compensate for water loss caused by osmosis. They filter out excess salt from their bloodstream through their gills and kidneys by urinating. For the freshwater fish, they don't need to drink water, but they do have to urinate. Because freshwater is hypotonic to the fishes living in it, water is continually entering their bodies through their gills, skin, or their mouths when they eat. To balance the amount of water in their bodies, all they have to do is urinate frequently. Wait! What? Does it mean than seawater fishes just have to pee more to live in freshwater? Fresh and salty water fishesAnadromous fishes are born in freshwater, but spend most of their lives in the ocean, only returning to freshwater to lay their eggs. Examples of these fishes include striped bass, sturgeon, smelt, and salmon. Catadromous fishes, on the other hand, live in freshwater but have to enter the sea through rivers to spawn. An example of a catadromous fish is the European Eel. Saltwater Fish vs Freshwater Fish Researches and ReferencesIf you want to know more about saltwater and freshwater fishes, take a look at some of our references below. Images we use are from Wikimedia commons, Patrice Laborda, Paul Cowell, and the Osmosis Draws and montage are from Marrielle Ferrer.
Speaking about fish, now I want to dive... Last, but not Least If you would like to receive interesting content like this in your email Inbox, subscribe to our newsletter. Thanks for reading, and if you wish, see you next week! The Research and Media Team at Scotty's. More Pictures About Saltwater and Freshwater FishesDo Fishes Pee Freshwater Fish Hypertonic Osmosis Draw Explanation Hypotonic Osmosis Draw Explanation Osmotic Pressure And Tonicity Saltwater Fish Saltwater School Of Fishes Why Cant Saltwater Fish Live In Freshwater And Vice Versa Discover Our ArticlesWhat happens if you put saltwater fish in freshwater?A fish that lives in salt water will have somewhat salty water inside itself. Put it in the freshwater, and the freshwater will, through osmosis, enter the fish, causing its cells to swell, and the fish will die.
Can all fish live in both freshwater and saltwater?Some fish species can live in both freshwater and saltwater. These species are called euryhaline fish. However, most fish species can only survive in one or the other based on their salinity tolerance, or how much salt their bodies can handle.
Can clownfish survive in freshwater?Unfortunately, Clownfish are strictly saltwater fish. You cannot put one in a freshwater aquarium, as it will quickly die. Clownfish live on reefs in the ocean, or sometimes in lagoons, mostly in the Indo-West Pacific Ocean.
How long can a freshwater fish survive in saltwater?A few species are able to live in brackish as well as fresh water and might live a while. But in general terms, a fresh water fish won't live more than a few minutes in salt water.
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What saltwater fish can live in freshwater
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