Manatees are another candidate. They spend most of the year along the coastal areas of Florida (I can’t remember if they are in other parts of the world) and winter in select freshwater rivers where the temperature is high enough due to springs. Crystal River and Homosassa Springs are two areas where they winter.
I believe Brown trout can migrate from freshwater streams to the ocean. Once they do they are given the appropriate title of “sea-run trout” although i think in certain places they are just called sea trout. It’s probably just a matter of reigonal dialects.
Thanks for all the info. I wasn’t thinking in terms of ducks or otters, but fish, reptiles and aquatic mammals like whales or manatees.
Many thanks.
I was under the impression that during summer they migrate north along the coastal areas of the Carolinas, Va., and areas further north, as far as Me., before making a U-turn back to Fla.
Actually we are both are correct, although you are more complete. IIRC many, perhaps most, stick around Florida although a lot do like to go farther afield. I guess it depends on how adventurous they are, how warm the waters are and what the food supplies are. I think there was one a few years ago that got trapped in a bay in Massachusetts (?) because it didn’t want to go into the cooler waters that had quickly appeared in the Atlantic and cut of the route back to Florida. I think it was captured and airlifted back.
(Please bear in mind that my extensive :rolleyes: knowledge of Manatees is from the brief talk given before we went snorkeling with them a few years back coupled with a mediocre recall of details.)
From here
http://www.earthsky.com/scienceqs/browsefaq.php?f=107
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In fresh water, a marine animal risks losing its internal salts to the outside environment. Very few marine animals have evolved ways to regulate their internal salt concentration in both salt and fresh water . . .
But **blue crabs ** can do this, to some extent. They’ve evolved a kind of “salt pump” in their gills that allows the crabs to keep the salt level in their blood constant – even in water that’s almost fresh. That’s important – because young crabs develop in sea water, while adults live in bays and estuaries where the water is less salty.
But even the remarkable gill pumps of a blue crab can’t draw salt from fresh water. So, to answer your question, crabs will die in fresh water because they can’t keep enough salts in their blood.