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Subject:

Re: Aeration of electrofishing holding tanks

From:

Franklin Wayne Poley <[log in to unmask]>

Reply-To:

Scientific forum on fish and fisheries <[log in to unmask]>

Date:

Sat, 5 Oct 2002 14:10:18 -0700

Content-Type:

TEXT/PLAIN

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Parts/Attachments

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Thank you-got it. Fish farming is a political hot potato here as the new
government has opened up fish farming to expansion as never before. We
need alternatives and that is why I was asking my admittedly naive
questions. So far I think the pressure to develop closed container methods
is the best compromise between those who would like to see no fish farming
at all and those who want unrestricted fish farming.

FWP

On Sat, 5 Oct 2002, James B. Reynolds wrote:

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>
> >===== Original Message From Scientific forum on fish and fisheries
> <[log in to unmask]> =====
> >><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> > If you reply to this message, it will go to the whole list.
> >><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> >
> >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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