As some of you may have heard a humpback whale has come up the St. Lawrence as far as Montreal. A woman described as a marine biologist was on the radio this morning. She claimed that an extended stay in fresh water would result in various problems, one of which was dehydration. Huh? This seems to make no sense. Can anyone explain how immersion in fresh water could result in dehydration?
Is it possible you might have misheard her? I know for ocean dolphins too much time in Fresh Water is bad for their skin, but dehydration does sound unlikely. They hydrate through what they eat anyway, not drinking water.
Perhaps she meant being beached or otherwise stuck and getting dehydrated that way.
This article discusses a whale that died in the River Thames. Dehydration is cited, and supposed to be from a lack of food which is how the whale would hydrate itself.
That article explains that the lack of food apparently caused dehydration since they get water from their foods. Seems that lack of food is the real cause. It’s not so much that she is wrong, but what she said is misleading.
If I hear any more about the whale I will update this thread.
Why couldn’t a whale get hydration from drinking fresh water, even if there is no food in it?
It may never occur to a whale to do that. A whale that drinks water when dehydrated under normal conditions would become more dehydrated trying to get rid of all that salt from sea water.
Might osmosis play a role? Whales are “calibrated” to live with a certain osmotic pressure from seawater, if the pressure changes due to lack of salt it may destabilize their equilibrium. Just an idea, pure especulation. Do not know if the effect would be anything more than skin-deep (blubber-deep?).
Food should not be the reason, many whale species go for months without food when they migrate from the poles to the warmer waters where they calf, they even breats feed for months without eating while swimming back to the poles. They can metabolize their fat reserves into energy generating water in the process.
IIRC It would be the opposite for ‘fish’, a fresh water fish put in salt water would dehydrate much like a person drinking sea water. For the other way around it would/may overhydrate whatever that term is as more water would enter then it can handle. Some fish can handle this transition however. Since this is for fish IDK how whales fit into this.