Are Captured Fish in Minnow Traps Safe from Electroshock?

While instructing an electrofishing short course in early 2017, I was asked if electrofishing near minnow traps containing fish would be harmful to them. When I asked “Why do that?”, I was told that electrofishing and trapping crews, in this case, work separately but in the same areas and often at the same time. To the question I said, “It depends on the material of construction. Minnow traps made of metal mesh are Faraday cages, but those made of non-metals are not. A Faraday cage in an electric field should protect the fish because there would be no voltage gradient (change in voltage over distance) inside.” If you were in a car struck by lightning, it’s not the tires that offer protection; it’s the metal shell you’re in. Even though a metal-mesh trap has holes in it, the mesh, if small enough, would divert the field over the trap exterior.

However, my curiosity got the best of me and I decided to test the theory. Continue Reading..

Two Backpack Electrofishing Questions Answered

Alan Temple and I taught an electrofishing course in Ft. Collins, Colorado last October. The course was unusual in that there were only backpack electrofishers, so that allowed us to have two field trips, in different habitats, using only backpacks. That permitted us to examine two questions – one pertinent to electrofishing in general, and one more specific to backpack units. This blog examines both questions and what we found.

Continue Reading..

Challenges of Conductive Substrates

Sometimes, things just don’t work as expected. You go to a new sampling site, determine ambient water conductivity, estimate a good starting point for standardizing by power and conduct a quick pretrial to fine tune the voltage, current or power levels for successful fishing.  But, either the starting point is incorrect, or the sampling begins successfully and then something changes to reduce effectiveness.  Below are three examples of unusual circumstances in electrofishing.  Two of these were my direct experiences; the other was reported to me.Continue Reading..

Course Announcement: Backpack Electrofishing Fundamentals

A new backpack electrofishing course is launched for Alberta, Canada by NAIT.

5137 Electrofishing Info Sheet[2]

Continue Reading..

Inside AFS 2015, Portland

Here’s a few pics of electrofishing porn from the American Fisheries Society meeting in Portland, OR, 2015. Lots of new goodies. Enjoy!

 

Standardising by power II

You can use this worksheet to apply your data collected in Standardising By Power I.Continue Reading..

Electrode resistance procedures

This document provides guidance for making electrode measurements on various gear types, using an external power source and an internal power source.Continue Reading..

How to use a backpack unit

Dr Alan Temple introduces the key concepts and methods of operating various backpack electrofishing units.

Trouble-shooting equipment

The following description covers basic trouble-shooting tasks that can be performed in the field. Some companies also publish in-depth trouble-shooting guides for testing control boxes and branch circuitry. Always obtain trouble-shooting guides from the manufacturer of your equipment, if available.Continue Reading..

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© 2015 Thread One Page. Imagery: Tom Rayner, Alan temple, Richard Pearson, Paul Godfrey, Roger Scott, John Rayner.