In fact, fish do not really need to feel thirsty to drink water. Drinking water is just a reflex that occurs without any decision from their body. Therefore, it can be said that fish never feel thirsty.

Whether fish are thirsty or not depends on their species. Because, saltwater fish and freshwater fish have different biological anatomy, which leads to different behaviors in drinking water.

Saltwater fish and freshwater fish drink water differently.

- Do freshwater fish drink water?

The salt concentration in the blood of freshwater fish is much higher than that of the surrounding water. Therefore, if freshwater fish drink water, they will face a high risk of blood thinning. That is why freshwater fish do not drink water.

Instead, they use the osmosis mechanism. Freshwater fish absorb water through their gills and skin. In addition, they also excrete much more diluted urine to remove excess water from the body.

- How do saltwater fish drink water?

Compared to the surrounding water environment, saltwater fish have much thinner blood. Therefore, to avoid dehydration, saltwater fish must actively drink water. With the advantage of having special gills, saltwater fish can drink seawater, process and excrete all excess salt.

Saltwater fish always actively drink water in any situation.

- What about fish that live in saltwater and freshwater?

Fish species that can live in both saltwater and freshwater environments are not very numerous. A typical example is salmon, which can migrate from saltwater to freshwater.

Baby salmon are born in freshwater, they will have to go through three major changes before leaving their birthplace to return home to saltwater. First, they will drink a lot of water. Next, their kidneys will reduce the amount of urine. And most importantly, the mechanisms in their gills will start working in reverse, eliminating instead of absorbing the salt in the water.

When salmon reach adulthood, they need to return to freshwater to spawn, they will spend a few days in an intermediate environment, also known as the tidal flats (shore waters or areas where the seabed is exposed at low tide). Here, their bodies will reverse the entire transformation process they had when they were young to be able to survive in freshwater. So the answer is that fish that can live in both water environments drink water.

No matter which environment they live in, fish need to drink water.

- Do other aquatic creatures drink water?

Fish actively drink, but not because they are thirsty. There are two reasons for this seemingly reluctant drinking. First, fish basically live in water, so their bodies do not have an urgent need to drink water.

For fish, thirst is a reflex that occurs without any brain-controlled urge. It is just an instinct. They do not necessarily feel thirsty to drink water. We all know that these creatures, like all other species, need water. The question to be clarified here is whether they drink water from the surrounding environment or not.