Do Fish Drink? Can Fish Get Thirsty?

Every human being has essential things to live. Undoubtedly, water is one of the most important ones not only for humans but also for many other living creatures. Water, a relative body component, makes up more than 60% of the body’s capacity. Water supports the activities of cells and organs but also helps balance body temperature and deletes waste products. 

However, we all wonder if fish can get thirsty and fish drink? In this article, we will solve all the consumers’ confusion about the problem: Do Fish Drink? Can Fish Get Thirsty?

What Is Thirst?

Thirst is the craving for fluids, resulting in the simple instinct of animals to drink, or we can say it is a bodily state that prompts us to drink water. The brain signals thirst if the body’s water volume falls below a certain threshold or the osmolyte concentration becomes too high.

Do Fish Ever Get Thirsty?

As far as we know, dehydration is dangerous for all living things on Earth because other body activities will be affected. Therefore, living creatures must maintain adequate amounts of water, and thirst is one of the signs that the body lacks water. So, do fish ever get thirsty? Well, the answer is NO! Fish do not need to feel thirsty to drink water like other living creatures. Drinking water is just a reflex that happens without any decision from the body. Therefore, it can be said that they never feel thirsty. In addition, it depends on what kind of fish you mention. Freshwater fish do not drink water because it will make their blood too thin. On the other hand, saltwater fish drink a lot of water to retain moisture. 

Aquatic Animals

Fish live their whole life in water, so how can an organism residing in water feel thirsty? Do you feel hungry when your house is still full of food? Or do you feel hard to breathe while air is all surrounding you? Those problems seem to be a little bit more complicated with fish. Fresh and saltwater fish have different biological anatomy that leads to erratic drinking water behaviors. The salt concentration surrounding a freshwater fish is much lower than in the blood of a freshwater fish. Therefore, if they drink water, they will be at high risk of having their blood diluted. That’s why freshwater fish do not drink water. Instead, they use osmosis. Freshwater fish absorb water through their gills and skin. In addition, they also excrete much more dilute urine to get rid of excess moisture in the body. Compared with the surrounding water environment, saltwater fish have much thinner blood. That is the reason why saltwater fish need to drink water actively. Thanks to special gills, saltwater fish can drink seawater and process and excrete all excess salt.

What About Fish That Can Live In Both Freshwater And Saltwater?

There are not many fish species with this ability. A prime example is Salmon, which can migrate from saltwater to freshwater. So, how can they exist in two completely different environments? Salmon are born in freshwater and undergo three significant transformations before leaving their birthplace to return home, where are saltwater areas. First, they will drink a lot of water. Then, their kidneys will reduce the amount of urine. The most crucial part is that the mechanisms in their gills start to work reverse, removing instead of absorbing the salts in the water. As Salmon mature, they need to return to freshwater to spawn, spending a few days in an intermediate environment, also known as intertidal flats ( coastal waters or areas with exposed seafloor). Here, their bodies will reverse the entire transformation process when they are young to survive in freshwater environments.


Do Aquatic Animals Urinate?

Everyone knows that fish can go poop. The main proof is the pile of sediment that appears on the bottom of the aquarium if you do not regularly clean it. So what about “urination?”? If you stop cleaning the aquarium, it will start to smell like ammonia. Then the answer is pretty obvious. Yes, fish do urinate. However, each different species will have another way of doing that. But the fish do it continuously. How does this happen? Most fish do it with their urinals or gills. Species urinating through the gills excrete urine that the kidneys have filtered.

On the other hand, saltwater fish “pee” through the gills, while freshwater fish use the urinary opening. As mentioned above, saltwater fish live in environments with a higher salt concentration in their bodies. Therefore, saltwater fish absorb large amounts of salt from their surroundings and need to remove it from their bodies. 

The main component in fish urine is ammonia. Ammonia leaves the fish’s body through the gills, which depends on what kind of fish we are talking about. Furthermore, fish urine contains organic acids, creatine and creatinine, amino acids, and trace amounts of urea. Freshwater fish urine is mostly water, while saltwater fish urine is mostly salt. Saltwater fish doesn’t produce too much urine, but it is highly concentrated.

In contrast, freshwater fish make a lot of urine. Fish urine is very different from that of humans. Fish urine is usually black or grey.

Do Fish Die If The Water Environment Changes?

Fish’s lungs have a different structure from the lungs of mammals. The fish will suck water into the mouth and use the gills to filter the oxygen in the water.

What if the water environment changes? Although the oxygen levels are similar, some substances would still be foreign to the fish’s body, and the concentrations can differ from what their body was adapted to handle. Their cells will either take in too much water leading to cell death. 

Can Fish Live Without Water?

People have defaulted to thinking that fish must live in water for a long time. Even though they have the form of fish, they can live in a dry environment for months without water. 

For example, Mangrove Rivulus is a particular fish in the Americas. This amphibian fish can live in both aquatic and terrestrial environments. In the summer, the water temperature rises, sometimes more than 40 degrees Celsius. The developed gills help them filter oxygen in the water and air. Blood vessels under the skin also help them absorb the atmosphere directly into the bloodstream more quickly.

Do Whales Drink Water? 

Whales are classified as aquatic mammals. They need to replenish their bodies by drinking or absorbing water from food. They have huge kidneys, which can excrete excess salt without losing moisture. And some other interesting facts about whales are they do not sweat or lose water when breathing. The air above the ocean’s surface is filled with water vapor, so whales do not lose water when living.

What Happens When Aquatic Mammals Drink Too Much Seawater?

This problem is quite complicated. If aquatic mammals absorb too much salt, they experience dangerous symptoms such as kidney failure, liver failure, and other movement problems. This is because mammals need to filter and eliminate excess salt when drinking water, which helps avoid internal damage caused by extra salt.

Interesting Things About Fish

  • We often hear about things on land that accidentally fall into the water but cannot swim and then drown, right? Well, fish that live in the water can still drown. Indeed, when living in water, fish also need oxygen to breathe, but if the oxygen in the water is not dissolved enough or the fish lives in a polluted environment, they will still drown as usual. 
  • Fish can swim backwards.
  • Some fish species can change their current sex during their lifetimes, such as blue-headed goby, blue-headed sea fish, parrotfish, or angelfish. This is quite an exciting discovery!
  • Fish can swim continuously without a break. Sharks and other fish will not have an air bladder to float on the water. Therefore, these fishes will have to swim continuously or rest at the bottom not to lose strength and lack oxygen for the body. 
  • Fish have no brains at all. They collect and process information through the skin cells that surround their bodies.
  • Goldfish do not have eyelids and have a terrible memory. Every 5 seconds that pass, the goldfish will immediately forget everything. 


The article entirely answers the question: Do Fish Drink? Can Fish Get Thirsty? Some fish species live in saltwater, and some live in freshwater. Although some fish can survive for several days on land, most will die if they cannot return to the water. The reason is that their lungs have a different structure from the lungs of mammals. When mammals breathe, their lungs are filled with air, and specialized cells filter the oxygen. The lungs will be dried and free of fluid during the process.

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