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Re: Electroshock procedures


John Wullschleger <[log in to unmask]>


Academic forum on fisheries ecology and related topics <[log in to unmask]>


Wed, 4 Dec 1996 09:25:39 -0500





text/plain (1 lines)

     Keep in mind too, that there is evidence that electrofishing can
     cause damage to fish. As I recall this generally seems to involve
     damage to vertebrae; often their is no obvious external evidence of
     injury at the time of capture. There have been some articles on
     this, mostly for salmonids, in some of the American Fisheries
     Society's publications (I believe Fisheries and the North American
     Journal of Fisheries Management) in recent years. I myself have
     observed fatal spinal damage in larger fish, specifically in grass
     carp of around 900 mm TL. Sorry, I don't have citations in front of
     me, but will happy to look them up if you don't have access to library
     resources. I believe that there are newer technologies that *may*
     reduce the odds of injuring fish but *may* also reduce effectivenes.
     That said, electrofishing is still often less harmful than some of the
     alternative methods.

     John Wullschleger
     Fishery Biologist
     Olympic National Park

>Date: Mon, 2 Dec 1996 14:40:55 -0800
>From: Craig Fusaro <[log in to unmask]>
>Subject: Electroshock procedures
>"Do (sic) to the irregular or rocky conditions electrofishing may be
>required... Fish will be collected using pulsed direct current with
>voltage set at 200-300 volt and 0.1 to 2.0 amps output... Pulse frequency
>and pulse width will be set to induce involuntary swimming action with
>minimum harm to fish."
>1. Is electrofishing really effective in five to ten foot water depth?
>2. Are the pulse voltage and current settings specified appropriate for
>these water depths?
>3. Would mortalities reasonbly be expected under the regimen described
>above, and, if so, what could be expected in terms of percent deaths?
Pulsed direct current electrofishing from a boat is definitely the safest
method from the fish's point of view. We have had considerable success
using our boat-mounted electroshocker (Model 7.5 GPP, Smith-Root, Vancouver,
Washington) in river water 5-10 feet deep. In fact we were pulling 6-8 lb
steelhead out of the Columbia River a couple of years ago. The key to
effective electrofishing is knowing the conductivity of the water you will
be fishing. We have fished with 900 W (300 volts at 3 amps) without any
significant mortality to larger fish. Keep in mind, however, that many of
the potential adverse effects of electrofishing are manifested over a
relatively long period of time. Since most of our work has been
catch-and-release, we have been unable to calculate a true mortality rate.
Good luck!

Tad Deshler
Tetra Tech, Inc.
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