Fish are often seen as the ultimate water-breathing vertebrates. They live in water all the time. However, do they drink water? Are saltwater species and freshwater species different? In this article, we’ll look at whether fish do drink water and why they need water in the first place.
Saltwater Fish Do Drink Water
You may have heard that fish live in saltwater and so they do not drink sea water. While it is true that saltwater is very salty, it is not true that fish don’t drink it. Saltwater fish do drink sea water.
The amount of water they need depends on the species and their size. However, invariably, all saltwater fish drink sea water.
Their body has less salt than the water around them. They intake salt water to process it by the kidneys. The electrolytes and salts are balanced in their body.
Saltwater fish kidneys ensure that the excess salt is excreted.
The kidneys are responsible for removing extra fluids and filtering blood, but they also play a key role in regulating the amount of salt in the body.
Freshwater Fish Do Not Drink Water
Freshwater fish do not drink water. They have more salt in their body than water outside.
However, this does not mean that freshwater fish do not need water at all. Water is still needed for respiration and hydration. But unlike saltwater fish, freshwater fish do not need to drink water.
Freshwater fish absorb water through the skin and the gills. A freshwater fish’s gills are covered in thin, hair-like projections called “cilium,” which help filter out particles in the water as it passes over them.
While it may seem counterintuitive, freshwater fish do not drink water directly from their environment. Instead, they absorb it through their skin and gills—a process known as osmosis. This is a process where the water enters the body through a membrane.
When freshwater fish are exposed to saltwater, the salts in the seawater cause these cells to become more permeable. Thus, more water passes into the body which would be fatal.
Osmoregulation & Osmo-Conformation
Osmosis is a process of water moving into the body of the fish and its expulsion thereafter.
In osmoregulation, fish regulate their internal fluids and electrolytes by controlling the amount of water lost from their bodies.
Osmoregulation is not dependent on external factors; it occurs to adjust the body internally.
Osmo-conformation occurs to adjust the body of the fish to external factors.
Osmoregulation in freshwater fish and osmo-conformation in marine fish are two processes that help maintain homeostasis in an aquatic environment.
Fish Do Not Feel Thirsty
Fish do not feel thirsty. The osmosis ensure that their bodies constantly get the required electrolytes and minerals. So, they do not feel thirst like humans do.
Fish constantly produce urine while they are alive, and it is released into their water. This means that their bodies are constantly getting rid of waste products (such as protein) and replacing them with fresh nutrients.
This keeps them well balanced in terms of their requirements at all times. So, they do not feel thirst like humans do.
The answer to this question is both a yes and a no.
Saltwater fish drink water, but freshwater fish do not drink water.
Saltwater fish and freshwater fish are not the same. Even their osmosis process is varied. However, both need water. Just that the manner of intake is different.