Do Fish Drink Water?


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I have a book sitting in my room that I’ve never read titled “Do Fish Drink Water,” and it made me curious…do they?

I decided to look into this more and identify the fish as the x variable, water as the y variable and the fish’s size, type,etc. as the z/confounding variable.

For this experiment, I also knew that this could be due to chance and that correlation does not equal causation in my results. I would take this as an observational experiment because you can watch the fish in their environment and how they interact with it.

I have found that fish do not drink water, but they get water through osmosis. In this process the water is diffused from a higher to a lower concentration. Since fish do not technically drink water and the water diffuses through the body from surrounding water in osmosis, fish do not need to drink water like humans. Their body is entirely different than humans and they do not need to drink water like us (8 glasses a day) to stay alive.

However, Aquaculture Specialist William Wurts, found fish need to drink salt water if they are in a salted body of water. Robert Kennedy of the University of Rhode Island also validates fish drinking salt water. This is because when drinking the salt water, the fish is replacing the lost fluids and getting rid of the excess salts. Interestingly in these findings, it was expressed that fish who live in fresh water, have a higher level of salt in their bodies than those in salt water- who knew? You would think that the salt water fish would have a higher level of salt since they swim in it constantly.


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Just like every living thing- it will need to properly function and in order to do that, fish must maintain a level of salt in their bodies. Additionally, there is always water being flown throughout the fish’s body correcting the level of salt making sure the level of salt is equal to that in the surrounding body of water. The fish needs to be balanced and not have too little salt because it could die.

When salt gets low in a fish, their kidneys work excessively making sure that the excess water leaves the body in the form of urine. The fish’s body is put into override mode to make sure the fish can get back to normal and live a healthy life.

Let’s take:

X Variable-Fish

Y Variable-Water

Confounding Variables- types of fish, size of the fish, etc.

We can take these and make an experiment and see how the fish live in his/her environment and conclude that not all fish need to drink water, but instead use osmosis to survive.

1 thought on “Do Fish Drink Water?

  1. Luyi Yao

    This topic is really funny. I know that the level of salty in body fluid of freshwater fish is higher than that in the environment, which means body fluid of freshwater fish is hypertonic solution. So water would be inevitably flew into fish’s body. Then the water would flow out from the body to maintain the balance of osmotic pressure. In fact, “drinking water” also has another purpose. The action of gill movement actually shows that fish absorb dissolved oxygen in water in order to breath. So osmosis also helps fish to breath. I like your topic very much!

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