Ladies and Gentlemen,

I have been a fisheries biologist for over 32 years, and have had the responsibility of sampling southeastern reservoir fish populations with electrofishing rigs many of those years. A number of folks who have responded to the original post have made very valid comments on the effects of electrofishing on fish. As with most things in life, there is much more to the story.

The electrical current put in the water causes a magnetic field. The fish are temporarily stunned and exhibit "syntaxis", which typically pulls their bodies towards the positive electode. Now all sorts of things come in to play during this activity. The species of fish, the size of the individual fish, the orientation of the fish when the electric field is energized, the depth of the fish, the proximity of the fish to the electrodes, the conductivity of the water, and many other paramenters determine how hard the fish is "hit" and whether it is indeed drawn to the surface to be captured.

Also, the electrical charge placed in the water typically is direct current (DC). However, in low conductivity waters (usually very oligotrophic waters), I have had to utilize alternating current (AC). AC is extremely dangerous to use, and I do not recommend its use if one can get decent results with DC! One other downside to using AC is that it is much more likely to cause spinal injuries to the fish sampled. I have witnessed fish hit by AC and, to a MUCH lesser extent, DC, to have spinal injuries as a result of the electrofishing. Proper setting of the control box of the electrofishing system is critical to prevent said injuries. That's where a good conductivity meter comes in handy prior to sampling.

In my surveys of reservoirs here in the Southeast, I usually try to get my unit to discharge about 7 amps into the water. That is enough current to severely injure or kill a human or your dog, if it is in the water. Ergo, the cautions to keep your dog out of the water. If you will observe, you will notice the workers utilizing lineman's gloves and, if wading, rubber waders to protect themselves from the electrical current. (Yes, I have used backpack electrofishing rigs in small streams. They'll zap you if you are not careful!)

I have witnessed some Hexagenia being temporarily affected by the electricity. They will usually recover quickly, as their body size does not allow for a great deal of electrical current to affect them. However, I have also accidentally hit muskrats, beaver, and cottonmouths before (they were underwater and not visible prior to being shocked). Let me tell you - a beaver that gets hit while at the edge of the electrical field is one whizzed-off critter!! Cottonmouths also get a bad attitude when they get shocked.

I hope this discussion helps answer some of your questions.

Gary