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The thread on aeration of holding tanks is interesting, and to expand it a
bit, I was wondering if anyone had noticed high delayed mortality in suckers
after "normal" stream electrofishing sampling for population estimates
(e.g., 3-4 passes in a block-netted section). cheers, gary



Gary D. Grossman
Professor of Animal Ecology
Warnell School of Forest Resources
University of Georgia
Athens, GA 30602

706-542-1160
http://www.arches.uga.edu/~grossman

Board of Editors, Animal Biodiversity and Conservation
Editorial Board Member, Freshwater Biology
Editorial Board Member, Ecology of Freshwater Fish
----- Original Message -----
From: "James B. Reynolds" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, October 05, 2002 2:23 PM
Subject: Re: Aeration of electrofishing holding tanks


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> >===== Original Message From Scientific forum on fish and fisheries
> <[log in to unmask]> =====
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> >Please excuse my ignorance but I am only a minor league politician
> (who is
> >sending this by bcc to some major league politicians). My understanding
> of
> >electrofishing (other than using electricity to stun and capture fish) is
> >that electricity can also be used as kind of fence for fish containment
in
> >open water. In other words it substitutes for the kind of pen which is
> >typically used here on the BC coast. But the pens now used contaminate
> the
> >surrounding water. So I was asking if there are electric fences which can
> >be used in open water and serve the same purpose as closed
> >containers...basically aquaria.
> >
> >FWP
> >
> The original question dealt with holding tanks for fish captured during
> electrofishing operations. The originator of the question used aeration in
> a a closed tank system, wanted to use a larger tank, and wondered if
> compressed air would work for aeration. I suggested going to an open,
> continuously circulating system which, in my opinion, is superior to
closed
> systems for fish recovery and sidesteps the compressed air issue
> altogether. The question of electrically-charged pens is not related to
the
> original question because holding tanks in electrofishing operations are
> meant to isolate fish from electricity and allow them to recover.
>
> However, the "pen" comment does bring up another approach: using
> metal-mesh, small pens in the water body (as opposed to on land or in a
> boat) to hold fish captured by electrofishing. The water inside the pen is
> not electrified even though it is immersed in an electrical field. This is
the
> Faraday principle and it is the same rule that says you won't be shocked
if
> you're sitting in your car when lightning strikes it. The metal-mesh cage
> allows flow-through, eliminating the need for a water pump, and the cage
> can be either stationary or floating along shore, or suspended from an
> electrofishing boat. The metal-mesh cage is not used very much because
> it is less robust than a tank and is less moveable with fish in it.
However,
> it has been regularly used between the pontoons of an electrofishing raft
> on the Colorado River (see Sharber, Norman G. and Carothers, Steven W.
> 1987. Submerged, electrically shielded live tank for electrofishing boats.
> North American Journal of Fisheries Management 7:450-453).
>
> Dr. James B. Reynolds
> Emeritus Professor of Fisheries
> School of Fisheries and Ocean Sciences
> University of Alaska Fairbanks
> P.O. Box 757220
> Fairbanks, Alaska 99775
>
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