Re: NANFA-L-- Re: Re: NANFA-L-- Re: Re: NANFA-L-- Old story,

Peter Unmack (peter.lists at)
Fri, 19 May 2006 14:48:14 -0500 (CDT)

On Fri, 19 May 2006 wrote:
> In a message dated 5/19/2006 1:17:16 PM Eastern Daylight Time,
> I don't think there is any data that supports your side. I have seen
> data that gives very little support to your general premise but for the
> most part the data is weak except when the fish is an obvious trouble
> maker like the flathead catfish or the peacock bass. Most releases don't
> result in much in the way of problems no matter how much you would like
> to see it.

You'd think that a species like a pleco that eats algae would be benign
wouldn't you? Not if you put them in a stream with fishes that may rely
on algae in their diet. Devils River minnow have essentially disappeared
from a stream near Del Rio in Texas within a couple years of plecos
becoming abundant. What about a fathead minnow? Pretty harmless huh?
Within three years of their first sighting they had virtually eliminated
recruitment in Gila purpurea in southern Arizona. We'd set minnow traps
for 20 minnows and fill them with chubs before fatheads got there. After
three years you'd maybe get one or two chubs and a million fatheads. What
about a fish that eats only plankton? That can massively alter food web
interactions that has trickle down effects on most of the species in that
habitat. Those are just a couple examples that I can think of off the top
of my head. I'm sure there are many more, although most remain

While granted, piscivorous species are clearly very very bad, it is only
because we see and can understand their impacts very directly. It is all
of the indirect impacts that are more subtle, but in the long term can be
just as devasting, but are much harder to see and understand.

There is a massive literature out there on introduced species and all the
problems they cause with all different types of critters and habitats (try
going to Australia and find a small native mammal in the wild).

And as someone else pointed out, it is very hard to identify what trouble
an introduced species may cause until after the fact when it is too late.

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