Although whales share the ocean with fish and other freshwater/saltwater animals, they are very different and require different circumstances to survive in the ocean.
Whales are marine mammals and make up part of the cetacean family, including whales, dolphins, and porpoises.
As marine mammals, whales breathe air, produce milk, give birth, and are warm-blooded animals.
Even though these marine mammals thrive in the ocean, whales cannot live in freshwater environments, at least not for long periods of time.
In fact, all known whale species live and thrive in saltwater environments rather than freshwater, and there are several reasons for doing so.
First, to help clarify this topic, there are a few species of dolphin that do live and survive in freshwaters, such as the Amazon river dolphin, Ganges river dolphin, and Indus river dolphin.
However, most species of dolphin live in saltwater, and there aren’t any species of whale that live in freshwater environments.
Part of the theory for why whales live in saltwater has to do with the assumption that whales and their prey have biologically adapted to the natural properties of saltwater and the fact that saltwater is often found in deeper environments than freshwater.
Saltwater contains salts and minerals that help clear out infections and aid in healing cuts or wounds that a whale may incur due to an injury or fight with a shark or killer whale.
Saltwater also contains most food whales consume, which generally comes from the ocean, not freshwater rivers.
In fact, one reason that could affect a whale’s ability to survive indefinitely in freshwater has to do with the fact that the whale would be unlikely to find sustainable quantities of food in a shallow freshwater environment.
In contrast to freshwater environments, the salty ocean is large and expansive, allowing whales to make deep dives where they can find sufficient food sources related to their dieting needs.
Whales that travel into shallow freshwater environments risk getting caught on land and can either become beached and dehydrated or, if the water is high enough, drown due to an inability to resurface for air.
Saltwater properties can also help the whale with rising to the water surf since saltwater has more buoyancy than freshwater.
Whales are hefty animals, so being able to rise to the surface using as little effort as possible helps whales maintain their energy and provides the best efficiency for being conservative swimmers.
Note: The blue whale is the largest animal on the planet and can exceed 300,000 lbs. (150 tons) when fully grown.
Some estimates state that a large baleen whale can weigh up to 180 tons.
Whales (especially those in large pods) need lots of space to survive and prosper in the water, which in most cases can only be found in the wide-open salty ocean.
Aside from these facts, many freshwater environments are littered with pollution, boats, and aquatic construction such as bridges and dams, fishing nets, and overfishing.
Even if a whale were to live in freshwater, these hazards would make it extremely difficult for them to survive.
Pollution
Chemical pollution and garbage can sometimes be found in coastal freshwater environments.
Both fish and marine birds have been affected by this pollution when swallowing the pollution or getting caught in it.
Boats
Rivers, coastal waters, and freshwater environments see continuous growth in private and commercial boat activities.
This increase in aquatic commuting can affect the marine animals that live in the area and even lead to collisions with large boats and ships.
Aquatic construction
The development of bridges, dams, and other types of structures in and around coastal/freshwater environments can cause segregation among pods and cut off essential food supplies for marine animals.
Fishing nets/gear
Marine mammals such as dolphins have been accidentally caught in fishing nets intended for other marine animals such as fish and squid.
These nets could also affect other cetacean species unaware of the fishing traps in the local area.
Overfishing
Fishing is prevalent in certain countries, and excessive fishing can lead to food supply shortages for marine animals.
Overfishing could affect local freshwater/coastal environments making it difficult for whales to survive in freshwater habitats.
As you can see, there are many hurdles whales would have to overcome to survive in freshwater environments beyond the improved buoyancy, healing properties, and expansiveness the salty ocean provides.
Fortunately for whales, they do not live in freshwater environments, so they are less likely to be affected by these changes that are occurring in certain freshwater habitats.
In fact, there has been a growing awareness that some of the freshwater dolphin species are declining due to the increased difficulty they are facing in freshwater environments, as stated above.
There are likely other unexplored and unanswered reasons why whales thrive in saltwater and why they become weak and unable to live in freshwater for extended periods of time.
However, the answers to these questions will only be uncovered as we continue to learn more about these amazing majestic animals.
To sum it all up, freshwater enthronements are too shallow to swim in, lack large supplies of food needed for survival, can be very hazardous to their health due to pollution, and are too small of an environment for whales to live in.
With that said, whales have been known to travel to freshwater locations on occasion and may pass through a freshwater area when migrating or traveling through the ocean.
However, they do not stay for very long and eventually return to the salty ocean.
Although whales cannot live in freshwater for long periods of time, there is an instance of a whale that goes by the name of “Humphrey the whale” that survived and lived in freshwater for several weeks, but eventually, he became very weak and sick.
Eventually, Humphrey, the whale, was guided back to the ocean with humans, boats, and whale calls from audio equipment.
Note: Freshwater environments in the ocean are rarely ever truly deprived of salt.
Even those areas considered freshwater tend to carry salt and other acidic properties, especially in highly industrialized areas, but to a lower degree than in true saltwater environments.
The highest freshwater levels come from rain, snow, ice, and mist and can be found in local rivers, streams, and ponds.