Do Fish Get Thirsty and Why Most Fish are Exclusively Freshwater or Saltwater Fish

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Have you ever wondered if other creatures share this aquatic dependency? For the scope of this article, let’s narrow down the category of ‘creatures’ to creatures that are surrounded by water all the time – fish.This may sound a bit strange, but do fish get thirsty too?

image credit: Today I Found Out

Fish, on the other hand, live in water. The question sometimes arises about whether or not fish drink. The answer is that they do; at least, many teleost fishes do. Fish that live in fresh water have blood with a higher concentration of salt and other solutes than the surrounding water.

image credit: scienceabc

Because their gills are in constant contact with the water, fresh water fish face a constant threat of their blood diluted, so they don’t use drinking as a mechanism to maintain the high solute concentration in their blood. Fish that live in salt water, however, have blood with a lower solute concentration than their surroundings and, like terrestrial animals, face a threat of dehydration.

image credit: wikipedia

Salt water teleost fish do drink to help maintain salt & water balance in their blood. They differ from terrestrial animals, however, in two respects. First, they don’t have to search for water; since they’re surrounded by water, they drink very frequently.Second, the neural circuits that control drinking are different in fish and mammals.

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In fish, these circuits are located in the hindbrain, but in mammals they are in the forebrain. Drinking in fish is considered to be a reflex and is thought to occur without any thirst arousal. Thus, although fish drink, that doesn’t necessarily mean that they get thirsty! Current thinking suggests that they don’t.

The other reason is that thirst, in fish, is more of a reflex that occurs without requiring a conscious decision on their part (unlike humans); it just happens. They don’t necessarily have to feel thirsty in order to drink water.