I was wondering how fish react to being electro-shoked. More specificly:
- Do different species/sizes of fish react differently?
- Do some fish die even when shocked by a professional?
- For how long do they stay immoble(in other words how long until they stap out of it)?
- Are they entirely immoble or do they still move around a little on the surface?
- Are they sluggish or disorented for an extended amount of time afterwards?
- Would threadfin shad sink when shocked due to thier lack of swim bladder?
- Can elctro-shocking stress the fish leaving them vulnerable to disease?
- Are there any other possible side-effcts of elecro-shocking that I should know about?

Thanks in advnce for the help.

posted February 14, 2003 06:02 PM
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I was wondering how fish react to being electro-shoked. More specificly:
- Do different species/sizes of fish react differently?

According to my literature larger fish are more affected by the electrical field.

- Do some fish die even when shocked by a professional?

Trout and salmon can be damaged by electrical shock. I have seen new studies that electrical shock can bruise and break the backs of trout and salmon affecting survival. Some agencies are backing off on electroshocking of trout and salmon.

- For how long do they stay immoble(in other words how long until they stap out of it)?
From my experience helping with electroshocking the fish (in this case bass and bluegill) twitch on the surface and when scooped up with a net and placed in a tank seem to remain docile for sometime. I don't know if a sedative was used.

- Are they entirely immoble or do they still move around a little on the surface? Most float up and twitch, some swim but are impaired. The ones barely in range sometimes swim away.

- Are they sluggish or disorented for an extended amount of time afterwards? Not very long when placed back into the water.

- Would threadfin shad sink when shocked due to thier lack of swim bladder? Don't know.

- Can elctro-shocking stress the fish leaving them vulnerable to disease? Any form of capture stresses a fish but they seem to recover.

- Are there any other possible side-effcts of elecro-shocking that I should know about?

Not side effects, but one must adjust electricity to the conductivity of the water. Too much conductivity is just as bad as too little.

just a little follow up. Very small fish often aren't as affected since they don't have enough body to carry the current through them. Also I have seen bigger fish give a power kick when they first get zapped and this can carry them outside the field where they quickly regain consciousness. Shocking is so fun, I think I'd travel around and do it for free if I had the money.

cecil,
Thanks alot for the info it's really helpfull but, when you say they remained docile for "some time" I'm still entierly qlueless as to how long that is. Could you please be more specific.

JB,

It seemed like it was enough time to fill the tub with fish and then pull over and start taking scale samples. I'd estimate 20 minutes. However like I said I don't recall if a sedative was used in the holding water.

This line of questioning sounds like a PETA setup to me.......That's one of there new things, how fish feel......lol. It's been proven that fish don't have a "functioning brain" that feels pain, but they keep attacking. Just a guess, but reread how all the questions are worded.

I may be wrong, but it sure was worded strange.

Just got back from vacation. I shock about 100 diff. ponds a year. This will help answer some questions I hope. Elongated species shock better i.e. bass better than bluegill. Bigger fish shock better but as mentioned my have the strentgh to kick out of the field and you may miss the big boy. Catfish shock poorly with a typical hanging electrode setup but great when conductivity is properly adjusted with bottom setup. I have fish that jump out of my nets and I have had large bass stay stunted for over 20 mins. The only fish I kill are young of year less than 2 inch bass. For some reason if I come across a group of them they will float up died. I feel elctrofishing is a low stress activity. They are swimming then they wakeup in a holding tank. Once relased after data collection they should be fine. I try not to do an analysis in the peak of the summer to reduce stress occurence. Many factros to consider making a professinal a must to get good results.

Jbrockey -- you got some good factual information from Cecil (trout are much more likely be injured if we aren't careful, compared to warmwater fish such as bass and bluegill), and Greg provided you with some background on his actual work.

I think the reason for the lack of a clear answer to your question is that electrofishing really is quite complicated, at least when it comes to electrofishing effectiveness.

In these electrofishing boats, we typically have some type of control unit. We can control how much electricity we put into the water. Thus, if we don't have an especially strong electrical field, fish are typically stunned for a very short time. For example, they may come around just as soon as you dip them and put them in a tank of water. If we have the field set at a very strong level, perhaps trying to reach a little deeper to get additional fish, then I have seen stunned fish that can take several minutes to recover. Again, too much electricity can kill fish, but biologists know how to avoid nearly all mortalities.

The control units also let us change the form of electricity that we put in the water. With one setting, we can be more effective on small fish. With another, we will be more effective on large fish. We can even do some funky things like use a unique setting to "tickle" up the big flathead catfish, much like the old telephone cranks used to do.

Finally, water chemistry can also play a role. Electrofishing is most effective when the dissolved solids (e.g., salts) in a water body are in an intermediate range. When water is very soft (few dissolved solids) or very hard (high levels of dissolved solids), then the same electrofishing field will not be as effective.

So, that may be more than you wanted to know!!

Dave

Brian,

No peta set up here. Stress is a very important thing to consider when raising animals of any kind. Depending on how much stress they encounter could mean the difference from them coming down with a stress mediated disease or death. Whether you are a recreational pond owner, fish farmer, or biologist you always want to keep stress levels down.

Lusk chimes in--
Electrofishing is an effective sampling tool, for warmwater fish. That's all it is, a sampling tool. Random samples allow us to qualify and quantify a fishery, provided our technique is adequate.
Electrofishing is dangerous. Hire a pro. Even if you could learn to do it, you still have to identify species and interpret the data.
Water does not conduct electricity. Quite the contrary. Water is an insulator. What's dissolved in water is the conductor.
The electric field is small, relative to the entire body of water. Shocked fish tend to quiver, because they are in tetany, but recover quickly, rarely longer than 10 minutes.
When the electric field passes over fish, they are quickly stunned, or thrust themselves out of the electricity.
Threadfin shad are stunned, but sit still in the water long enough to dip. If left alone, they begin to sink slowly, but quickly revive and move on. I don't pick them up, due to their delicate nature. But, I do a quick count, and log the data.
Mortality is rare. In fact, I have only seen young of the year bass die. Hit a school of newly hatched baby bass, 8 or 10 die. I have never seen any other species of warmwater fish die due to electrofishing.
But, if water is highly conductive, and the voltage is too high, more than 10 amps can break the spine of channel catfish. That's quite rare, too.
Different species react differently. So do different sizes of different species. For example, largemouth bass are easily shocked. Bluegill are, too. Channel cat, when in shallow water, are easy. Grass carp are tough. Their muscle configuration allows them a quick burst, enough to escape the field. Gar are tough, too. Shaped like a tree limb with teeth, gar can quickly evade with one burst of their tail, like a wet arrow under water.
Considering the benefits of data collected via electrofishing to the down side, I overwhelmingly favor electrofishing. The data is invaluable.

Thanks for all the great info guys (and don't worry Dave, more information is always a good thing)
-Scott