As everyone knows, fish live under the water but the question is, do they drink water, and do they get thirsty?  

The simple answer is yes, they do drink water but it all depends on the type of fish.  Technically freshwater fish do not drink water because it can lead to their blood getting too diluted.  

On the side of the coin, saltwater fish do drink a lot of water to keep themselves hydrated.

Thirst: What Is It?

In the basic sense of the word, this means the urge to drink.  This is a human’s way of making sure that their balance of salt and water is maintained inside their body.  All animals, except fish, are faced with the threat of dehydration so the basic instinct is to drink water.

1. Aquatic Animals

Thirst in aquatic animals that live in the water is an entirely different thing.  Both seawater and freshwater fish show different behaviors when it involves drinking water.  It is related to the anatomy of their bodies.

water fish

2. Seawater Fish

The salt concentration in the blood of saltwater fish is much lower than the water that is surrounding them.  Seawater is highly saline so seawater fish are constantly threatened by dehydration.  As a result, seawater fish actively drink water.  Due to the design of their gills, the saltwater fish can drink the saltwater, process it through their mouth and gills, and then eliminate the excess salt through urination.

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3. Freshwater Fish

These are the fish that are living in fresh, non-salt water and have a blood concentration of salt than the water that surrounds the fish.  If these fish drink water then they have the chance of having their blood diluted. 

This is why these types of fish do not actively drink water because they do not need to in order to maintain the balance of water and salt inside their bodies.  These freshwater fish will absorb water through their gills and skin by a process called osmosis.  They will then urinate a mixture that is a lot more diluted to get rid of all the excess water.

4. Fish That Live in Both Environments

Although there are many fish that fall into this category, there are some fish that migrate between freshwater and saltwater.  One such fish is salmon.  The questions are how do they survive between saltwater and freshwater and do they drink the water. 

Salmon are born in freshwater and during their growing, up time they will go through three major changes before they leave their nursery in the freshwater for their saltwater home.  The salmon start by drinking a lot of water and then their kidneys start to decrease their output.  

The most important thing that happens is that the mechanisms in their gills start to operate in reverse.  When this happens the gills start to rid the fish of the salt instead of taking in.  After they return back to the freshwater after spawning, they will spend a few days in an environment that is neutral. 

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This is called an intertidal zone (marine environment).  It is a seabed and foreshore area that is submerged at high tide and exposed to the air at low tide.  At this time, the changes in the salmon are made in reverse so they can live in a freshwater environment until it is time to spawn.

Do Fish Get Thirsty?

Yes, they do drink water actively but the other question is, do they get thirsty?  The answer is probably not.  There are two reasons for this.  One is that mammals on land do have to have to actively seek water in order to stay hydrated and fish live in water so they do not have that strong urge to drink water.  The other reason is that for fish, thirst is more of a reflex that happens without them requiring a conscious decision to drink water.  It just happens naturally so they do not have to feel thirsty just to drink water.

fish drinks water

Do Other Water-Dwelling Creatures Drink Water?

Fish are not the only water-dwelling creature in existence.

  • Whales:  These are considered marine mammals and they do need to stay hydrated by drinking water.  They get the water from their meals and their surroundings.  They have huge kidneys that allow them to excrete any excess salt and they do not lose a lot of water.  They also do not sweat so they do not lose any water when they are breathing.  This is because the air that is above the ocean is full of water.
  • Dolphins:  These are also marine mammals and they are not sure just how they consume water but it is thought that they get it from their food as whales do.  Dolphins also devour aquatic animals so they do extract some water from their bodies and this is much better than drinking saltwater.  Another theory is that when they devour their prey they also take in the water that surrounds them.  They also have a highly advanced filtration system.
  • Turtles:  These are reptilian creatures that live in both water and on land.  Since they do spend a lot of their time on land they do need to make sure they stay hydrated so turtles do drink water.  Often they drink the water that they wade or swim in but the turtles who reside in the salty ocean do have to filter out the salt in their water.  To do this, they have a special gland in their eyes.  It is called their salt glands. When they are drinking salt water the salt will enter their blood and then carried to their salt glands through their bloodstream.  In the salt glands, they produce a solution that is twice as salty as the salt water, and then it will come out the body through the corner of their eye.
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Conclusion

  • As humans breathe, they lose a lot of water.
  • Octopus, squid, and some other fish already contain a lot of water so they do not need to worry about getting it from their food or environment.
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