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Re: Now Never returned to the wild
On Thu, 9 Jul 1998 Moontanman at AOL_COM wrote:
> No, I was trying to underscore that we are not the main or even a major
> contributor to the spread of aquatic disiase.
My only point here is that the aquarium hobby has increased the spread of
disease around the world. Birds have been doing it since year dot, hence
whatever they could have spread has been spread. Birds don't act as a vector
for every disease though. Many transcontinental movements of diseases are
impossible as most freshwater disease organisims cannot tolerate salt water
nor complete desication. Hence many continents have their own suite of
diseases. Once you start moving the fish around you complete change the
playing field as that former barrier is now removed. Release that on a new
continent and then birds are probably far more likely to move them all over
the place.
> Water fowl fly from continant to continant
I think I adequately addressed that issue above.
> , turtles, aquatic mamals and
> other organisims migrate from stream to stream, and most water sheads are
> part of huge dranage systems that are all interconnected. All these things
> contribute to the spread of any aquatic organisms much more profoundly than
> humans except eviromental degredation.
That is my whole point. Once a new disease gets in you cannot stop it moving
around for the exact reasons you list above.
A little example to stress my point. In the White River Valley in Nevada
there are a series of springs with springfish (Crenichthys) in them. In the
middle of the Valley there are three springs all within a few miles of each
other. All have exotic fish such as mollies, convict cichlids, and damnbusia
in them. The middle spring, Crystal has an infestation of anchor worms
(Lernea). The springfish population is this spring is severely depressed
likely in part to heavy infestation. The disease has been present for many
years and likely came in with aquarium fish that someone released in there
(which based on what is there today are all North American species). It has
not spread to any of the other springs or nearby waterways. The specific
anchor worm is originally from Asia and it was introduced very early on and is
now found in most parts of the USA (and Australia too). Some native fishes
are quite susceptable to this crustacean parasite and suffer major
infestations which weakens their resistance to other environmental factors in
addition to secondary infections by other diseases. There are still many
places that do not have this (suggesting that birds are maybe not an all
effective dispersal agent at least over the short term).
> Polluted water and weakened immune systems of the fish that live in the
> pollution give rise to new pathogens, It is a rare event for a pathogen to
> have a major effect on heathy populations of fish in natural unpolluted
> conditions (non-aquarium or unaturally crowded)
Fully agree.
> I'm sure it occurs, but I
> doubt humans have much influence one way or another.
Much influence? That implies there is some but not a lot right? That is my
whole point, disease introduction is a risk that can be easily reduced by
simply not rereleasing fish.
Tootles
Peter Unmack
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