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Re: NFC: ecology 101

Evil Moon. :)

The biggest, and rather obvious, problem with that line of thinking is tht
very few organisms occupy just one "niche."  For instance, the well knwon
Chinnese Algae Eater would seemingly make a great addition to streams with
algae problems.  Its a more or less cool water fish, doesn't get big,
eats lots of algae, and is relatively attractive.  However, as they grow
up, the CAE doesn't each as much algae, and turns to carrion instead...
Larger individuals may even provide their own sources for it.  When young,
it occupies the algae eatin' niche.  As it developes, it goes to a carrion
and tehn carnivore... and at times occupies many of these niches.  
Then, theres the other issues associated with it.... first, what niches
does it effect?  We'll keep with the CAE for a bit.  A whole bunch of baby
CAE's are going to compete with many other fish fry that also depend on
the algae for food.  Plus, all the CAE's wiping phytoplankton from teh
rocks may remove a habitat for egg layers to lay eggs in.  Also, these
phytoplankton now aren't acting as a filter.. the BOD in the stream will
go up.  Perhaps cyanobactera will get a foothold now -- something the
CAE's won't eat.  Worse yet, it might be a toxic variety.  Somewhere
downstream, someone may be taking water from the stream, and get sick from
teh toxins released.  Or, perhaps the stream passes thru a park, where
people walk their dogs.  Not knowing better, the dogs drink the water, and
may die.  Not to mention that cyanobacteria is ugly and stinks. Next, the
CAE need places to hdie and such.... they often use underhangs of stone
ledges and such... sound familliar? So do our cave spawning darters, for
example. They'll easily displae those, robbing them of another egg laying
site.  Now, the CAE's were imported from somewhere, perhaps with
parasites?  You can see where I'm going here.
To choose your example, the Red Bellied Pacu, theres quite a few obvious
problems.  One, the Pacu grows enourmously large.  It would compete with
game fish for space.  Pacu don't eat just vegetable matter, I've seen
plenty take fish, crawdads, and so on.  Thats food for the gamefish.
Plus, it removes some of the fish int here. They'll also only work in
larger systems, due to their large size. They're also a massive fish
that'll produce large ammounts of BOD thru its waste, as well as when it
dies.  Lastly... the Red Bellied Pacu looks like a pirahna... most people
won't take the time to learn the difference... its happened plenty of
times before. :)

 J. L. Wiegert                                    ICQ UIN: 1918889
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