Whales are not considered capable of living in fresh water for long periods of time.
How long whales live in freshwater has become a subject of debate with numerous visits by whales to freshwater environments. Interest in this topic peaked when Humphrey the humpback whale made a detour into the Sacramento River in 1985 during the whale’s annual migration season. Humphrey managed to spend several weeks in the brackish (freshwater) water of the Sacramento River before finally returning to San Francisco Bay and then the Pacific Ocean. The matter was revisited in May 2007, when a humpback mother and her calf entered the Sacramento River.
Humpback whales entering the Sacramento River have given rise to speculation about their survival in freshwater.
In general, some experts say it is unusual to see whales in freshwater for more than a few weeks. There are a few species of dolphins that are specifically freshwater mammals, but most whales were built for saltwater environments. Scientists aren’t sure how long whales can live in freshwater, as they are saltwater mammals. One problem is that in freshwater, they don’t have access to their regular food sources.
Although often associated with the ocean, dolphins such as the river dolphin can sometimes live in fresh water.
An additional concern for whales in freshwater is that saltwater performs some natural functions for the whale. Small cuts or scrapes, for example, are easily healed with salt water. Freshwater environments do not provide access to the beneficial healing aspects of salt. It was noted in the May 2007 incident in Sacramento that both whales appeared to have been injured by a boat propeller. Fortunately, the two whales in this case were driven back to the Pacific Ocean about two weeks after they made their appearance in the Sacramento Delta.
Freshwater environments are also unnatural for a whale’s swimming and diving activities. Most whales swim in waters at least 6.1 m deep, if not considerably deeper. Freshwater rivers can be just a few feet deeper than the circumference of a whale’s body. This makes them more likely to run aground.
The humpback whale and many other species of whales are migratory animals by habit. Deviations from typical migration patterns can create problems for whales. As they are not used to the route they are taking, whales can get confused easily. The migration instinct is innate, so as interesting as it is to see whales in fresh water, it is a matter of concern for whale lovers.
When possible, governments and environmental groups use their resources to help whales return to their natural environments as quickly as possible. Marine biologists are certain that whale biology cannot survive indefinitely in brackish water and that at most few whales in fresh water will survive more than a month.