Marine Mammals and Fresh Water habitation

Dolphins do live in rivers, though pollution (especially in China) has rendered most river dolphins extinct.

Dolphins, whales, seals, and other marine mammals have to live where there's enough food and clean waters - salt content is immaterial.

Other than your name - where did you get it, btw?! - I'd like to welcome you to our website. You're right to worry about our very close relatives, the marine mammals, as many of them are endangered:

Zoning regulations.

Paranoia?

Almost every continent has a marine mammal or two that have become adapted to fresh water environments. They often start out as "adventurers" that leave the marine environment and travle up the larger esturaies and then feeding rivers.

Several adaptations that have been studied are the adaptees loss of the ability to extcrete excess saline from their systems. (Im not certain that all of the river dwellers like the AMazon Dolphin have lost this ability).The "dome" , the bulbous mass for echolocation changes due to the sediment load in the new environments. Im not sure how this changes but, in the cases of sound propogation, the echolocation may take a on a loer frequency for greater distance location. Also the "flippers" have modified into longer appendages that can be used for bottom "skipping" .
In essesnce, these are animals that may be returning to lives of their ancestors.

Now there are several marine mammals that have partially adapted to fresh water environments, (a few of these are in the North and S American areas). Dolphins and some whales live parts of their years in fresher water estuaries and then return to the saline waters during migrations.

Id say, and this is a guess, that the biggest obstacles to continuous life in fresh water are mwechanisms for dealing with the salinity changes and also navigating in more turbid wters, as well as having the animals horizon defined by the river cross section when out in the sea, there was little problem with open area navigation.

There are several fresh water seals in the world. The closest I recall are the population in Lac Loup in Quebec. These are fully fresh water adapted seals.

The manatee is also a marine animal that lives both in salt and fresh water in its travels.

beat me to it Linkat

Living in S Florida I get to see them when I'm out sailing in the Indian River Lagoon.

Aren't they just awesome creatures! I would love to see one like you have. My daughter had to do a report on an endangered species and she chose the manatee. She so much fell in love with them - that she took all her money to adopt one - she didn't have quite enough but because she was so thoughtful I paid the difference. She actually said - it was more important to help one of these animals than for her to get any old toy or other thing.

Here in S Florida things have gotten much better for the manatee. No wake posted speed limits have slowed accidental manatee deaths.

Quick story.The cooling water effluent at Ft Pierce Utilities Station attracted Manatees in the winter...from way back in the 70's. Eventually they built a Manatee Center where you can watch them hang out

If you ever have reason to come to S Florida be sure to check it out

I have heard about that. And I did tell my daughter the next time we are FL, we will try to see the manatees (of course depending if they are in the area at that time).

Did you know that Rae introduced me to a manate when we were in Cocoa Beach? We saw the "Don't Feed or Pet the Manatees" sign to late to do anything but feel guilty.

I didn't know that....good times