>Lake Nicaragua is home to the only species of shark that inhabits
>fresh water, the Bull Shark. And of all the sharks I have encountered
>while diving, the Bull Shark is the most dangerous. A Bull Shark
>attack recently took place in less than three feet of water, with the
>shark propelling itself from deeper water almost on to land to attack
>a person. So be careful when you're reaching into the water for that
>really interesting snail! That, unfortunately, is my best tip.
In fact sharks live well up both the Amazon and Ganges rivers, and no
doubt many others. Their metabolism allows them to pass freely
between salt and fresh waters. That isn't just the bull shark
(Carcharias taurus) but others as well, including Carcharodon
carcharias (though the latter must be a long way from home, as they
are territorial inshore dwellers who live near seal colonies). I have
heard that the Nicaragua and Ganges sharks are particularly hungry.
The Amazon ones probably have plenty of fish, crocodilians and snakes
to eat and so don't bother with queer-looking humans.
Now, I have HEARD that Lago Nicaragua is full of marine taxa which
have adapted to freshwater. But there appears to be no literature
(not that I've done a Google search yet). OK, just Googled ... so
much rubbish! Archeological stuff and sharks... cichlids collection
catalogs... blogs... ... tourism and old expeditions... relationship
between Iran and Lake Nicaragua... NOTHING on the molluscs
themselves... AAARGH!! I would be most interested to see images of
the molluscs, or exchange for specimens.
When I visited Newfoundland in 1990 I had done little freshwater
collecting, apart from wading or floating in a skiff on St Mary's
Lake, Saltspring Island, near Victoria, BC on a number of occasions.
In NF I met Ron Noseworthy, who introduced me to the Walker dipper.
This is a lightweight piece of wood dowelling or aluminum tube with a
stout kitchen seive wired onto one end by its handle. This can be
used to scoop up visible shells or to swing through sand or weeds to
collect shells living out-of-sight on these. I'd say that this would
probably be a very advisable tool to use in this lake!
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
Seashell, Macintosh, VW/Toyota van nut
‚ Opinions stated are mine, not those of Otago University
"There is water at the bottom of the ocean" - Talking Heads
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