Electrofishing

[Guest]

So I'm reading through some more DNR reports on some lakes and I came across the word electrofishing just as I had done manytimes before. Well this time I decided to find out exactly what it is. Maybe I'm the only one in the dark here but oh well I guess. Turns the DNR uses the technique To shock fish and then collect and count the ones the float to the surface. Its primarily used for trout and bass and other common shallow water fish that a net can't get at. Now I'm no tree hugger by any means, but as I read a few articles it seems that quite a few fish don't make it through the paralysis. Wouldn't the shock it takes also take out the bait fish too? What about the lakes and rivers with low counts of fish? Should this b standard procedure? Anybody know anything, or was everyone in the dark with me?

[rmh2o]

Ive seen them out doing this in Mille Lacs but I dont no what the mortality rate is,ive only heard that it temporarily stuns the fish

[fiskyknut]

I've seen them in action on the Red river. Can't comment on mortality rate but they sure get the fish! I could'nt believe the numbers of this, that and the other things that were floating. That Red river is FULL of fish of all kinds thats for sure.

Fisky

[cwmn]

This is a very common thing down south, Florida and Alabama, and from what I have raed the mortality rate is very low, the biggest thing is it is done in the spring before the water gets too warm so the fish have a better chance of survival. It's certanly better then a gill net or trap net that have almost 100 percent mortality.

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Have a good one!
CWMN

[Jim W]

Bigguns1,

There is a vast misconception in the process of electrofishing. There is NO shocking taking place. However, the process can result in some fish inadvertantly sucumbing, but it is rare.

During my Trout Day in SE MN, I have had the opportunity to bring in Fisheries boys to demonstrate electrofishing.

My description will probably confuse more than clarify, but I will try.

What takes place is, fish react to electical current placed in the water. It's not like they have some souped up batteries with heavy duty cable then turn it on full charge.

There is a neutral/negative end with the current moving out to a positive end. The fish gravitate towards the positive charge, allowing for netting.

SOmetimes the fish will get caught directly in the middle of the power field, momentarily paralizing or knocking them out. Most revive!

If that makes any sense, great. If there are some Fisheries people out there who care to give the scientific explanation feel free!

I might have the charges etc. reversed but the process is right on.

Keep the rods bendin!!!

Jim W

[This message has been edited by Jim W (edited 12-19-2002).]

[doubleUcubed]

Jim, did they use the "backpack" or "boat" set up? I have also seen the set up that they had/have at the outlet of Koronis. That setup had the wires strung across the outlet and when the fish were in the current they would "stun" them and they would wash over the spill way into their trap and the game fish would be removed and placed back into the lake. On the lakes around here they have used the "boat" mounted stunners and at night they will go out and slowly move about with the boat and stun the fish and count them on the surface. From what I have heard the mortality rate is very low. Certainly anything is better than a gill net. The hoop nets are pretty good for survey's. Just my .02 cents worth!!

[Guest]

I got this all messed up,.... from what I read,.... It says that the fish are shocked or stunned or zombiefied or whatever similar to the effects of a tazer or something. From what i read what you said is true however I understand it in a different order. The fish are attracted to the field and then stunned when they get into the middle of it. I don't think that the fish just "feel the force" and then swim to the net like zombie fish I could be wrong,......probably am

[Guest]

I did a summer internship with the DNR electro fishing all of the large rivers in Southeastern Mn. Jim W is right is only makes them swim towards the surface. You have about 3 seconds to net the fish before it swims away.
Mortallity is due to more factors such as weather (heat) and the handling of the fish mot the shocking itself. Many things influence how hard the wave hits the fish. Shape and size of the fish are the most common. Bigger fish get hit harder due to more surface area. But the samller species like darters and some minnows can't handle the shock. When this happens the juice must be turned down.
There are some beautiful fish still swimming in those rivers.

[K2]

i have been electroshocking with the DNR in MN and the mortality rate is very low. the electricity 'paralizes" the fish for a moment or two, the longer you stay on the button the more juice they get. you scoop up the fish you wish to sample. after taking the measurments and scales we needed we placed them in a holding tank on the boat until they showed enough life to go back into the water. of all the trips i was on we didn't have a fish that didn't swim away.

we did it at night with spot lights in the shallows. many different fish sampled- walleye, northerns, muskie, bass, and the larger panfish. we were usually looking for young of the year fish to check for natural reproduction.

in my opinion this is better than gill nets, which has a total mortality rate, and the fish taken out of the nets are not given to food banks, they are discarded.

[Guest]

Bingo, shock surveys are far more fish friendly then nets.

Some species are not good candidates for shocking surveys, so nets or trot lines are employed to get the needed data.

Catfish are one example, they are too darn suborn to get zapped, especially the large adults. Factors like suspended particulates may effect the process and limit it's productivity on murky rivers, this may be the biggest problem in targeting cats.

Set or trot lines are frequently used under those conditions. They are rigged with barbless circle hooks, the lines are monitored closely. Surprisingly the trot lines, well supervised, have a very low mortality rate.

------------------
Ed "Backwater Eddy" Carlson..><sUMo>

Backwater Guiding
"Ed on the RED"
(701)-281-2300

[email protected]

http://ed-carlson.fishingbuddy.com

[Jim W]

DoubleUcubed,

Hey,
At the first Trout Day they used the back pack. Last year it was "the boat"!!
This year...dynamite!!!LOL
Later
Jim W

[Pig_sticka]

watch in years to come we will just stick the electo in the water and grab whatever fish we want. fishing rods will be history. hey pa i just zapped a 12 pound sunny come over here n net it. naw too small son lets let it recover n send er back. bbbzzzzzz eh got another one they are hitting good today. just upgraded to 500 watts of power with the dr500 works great. bbzzzzz

[Guest]

But what about the science behind it? What brings them in? And what brings them to the surface?

[Jim W]

Bigguns1,

I'm not sure even the DNR can explain why exactly fish respond to the electrical current. Correct me if I'm wrong people, but it is a phenomenon, regarding why fish move towards the "cone".

As far as them coming to the surface, it is a reaction to the current itself, causing spasms etc and shutting down or briefly knocking them out.

At last years Trout Day in Forestville State Park, the "run" that the DNR were deomonstrating in had a large population of suckers and chubs. Considering the debris field of suckers following behind I would have to confidently say these fish weren't harm.
THere intentions were not to kill off suckers littering one of SE MN premier trout streams!
They eventually all came to.

Feel free to join in on the 3rd Annual Trout Day and see for yourself!

Jim W

[doubleUcubed]

Jim, ever see 3 semi loads of carp take 440!!!!! WOW!!

[Jim W]

That is some lips!!!!

[Reefdawg75]

Bigguns1,
Back in college I did some volunteer work for the DNR which included electro-fishing. The boat they used consisted of a flat bottom boat with a gas powered generator. The generator ran spot lights up font /sides of the boat (nighttime electro-fishing) and two 12 foot PVC pipes off the front containing an anode and a cathode to create the electric field. The field is most effective in 5 - 10 feet of water around and under the boat. Electro-fishing was done in short intervals (on and off). The person driving the boat will hit a foot switch creating the electric field for 3 - 15 seconds. Meanwhile, two others reached with 10 foot long nets and scooped up stunned fish and place them in the livewell. The trips I was on was to survey bass in metro lakes.
It was interesting to see the fish's reactions to the electric field. Most fish could sense the field and try to scurry away. Large fish, primarily northerns, were fast enough to avoid the field. The majority of the fish that were stunned consisted of: panfish, baitfish, bullheads and Bass. The stunning part was very interesting. When a school of fish would enter the electric field they would freeze up, yet thier inertia would keep them traveling forward criss/crossing in the water. Hundreds of baitfish swimming in formation would seize up and glide in random directions. It would be similar to watching the same shapes fire works create falling in the sky only baitfish in slow motion rising to the surface. Then the field would pass and the fish would regroup back to normal. All of the fish that were surveyed were released with no problems.

[K2]

in response to the question "what attracts the fish to the field", they are not attracted to the field they are caught in it. the electricity causes the muscles in the fish to contract, much like when you grab a electric cattle fence you can't let go. if a fish is to the right of the field the muscles on the side of the fish exposed to the juice contract causing the fish to swim in a circle or into the field until the muscles run out of energy then float to the surface to be netted by researchers. if the fish is between the electrodes then both sides get hit and the fish is 'paralyzed' of floats up to be netted.

when we shocked we had muskies up to 45" pop right out of the water and into the boat. the larger the fish the more jucie it gets and they get a good zap. one must remember that humans can get zapped too. we had to be dressed from foot to chest including arms and hands in neoprene suits to keep from being shocked, touch water or boat and you get a shock too while the button is being pressed.

it is a very fun experience, being out at night in the shallows with powerful spot lights and seeing all the fish. amazing how the fish are not all scared by the boat motor, generator noise and lights.

K2

[cyonko]

New York DEC uses electroshocking in a lot of the lakes and streams to get numbers, sizes, and species reports. They then turn these numbers around and use them to set size and take limits as well as to establish stocking numbers for each species. The mortality rate is very low especially for species such as trout. NY DEC allows the public in certain instances to help out with the "shocking" and in others it puts when and where "shocking" will occur in the local papers so the public can come out and watch. I have been to several streams to view the process its amazing to watch little boys and grown men eyes pop wide open when a 5 lb brown trout come to the surface in a stream no wider than 6 or 8 feet.