Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Shocking clear low conductivity water

HELP! The new shock boat is working like a champ. We have been getting good numbers of all species and some really nice bass with several over 6 lbs in pond evalued in the last few weeks. HOWEVER I drove all the way to south of Asheville, NC (8 hr round trip) and got no fish.

The client found me here. I was pumped about job b/c I have only on a couple of occasions shocked any smallmouth. I thought I was up front if water is too clear it is difficult. Well it was 13 ft visibility accoring to Cary Martin who joined me for the job. Also alkalinity was less than 4 ppm. SO ultra low conductivity. I knew I was up againsit it when I started and would not have driven up there with boat had I known it was that clear. It cost me alot of money and client was not happy. We did observe fish and lack of forage so I will write report according to those results. I feel confident in what is going on but client was upset and said basically will not use me. I have never had that happen.

QUestions anything I could have done different? Cary spoke with NC DNR and they suggested throwing out salt to quickly boost conductivity for short period. Also stated it is just extremely difficult. I spoke with some other DNR folks and they simply said with that conducitivty it is not possible. So do I not shock clients with clear low alk ponds?

Any advice on techniques to get better wattage into the water in "distilled water" would be appreciated. In the past our old boat was small and we were able to get some fish in some ultra clear lakes. This boat is nice but frustrating it works less effectively in the clear water. Help?

HI Greg. Did you take a conductivity reading? That would help. Also, do you have a brand name and model on the control unit, or is it something that someone constructed?

I'm not an expert on low conductivity, but just by default (geography), I'm an expert on too high of conductivity and effects on electrofishing. Let me toss a few ideas at you.

First, you didn't say, but it sounds like you shocked during the day. With water that clear, I always try to electrofish at night, no matter what the conductivity. In low or high conductivity, where electrical fields are not ideal, it's a necessity. So, one thing to try is to shock after dark. I suppose that's not ideal for your work hours or the client viewing everything, but tough circumstances call for tough techniques.

Second, in low conductivity, you want as much surface area as possible on your electrodes. How is your boat set up? Is the boat itself the ground? If so, good. Then, what about the positive electrode? Does it have ring electrodes with droppers? If so, make the droppers twice as long, and put on twice as many. Heck, you can even use higher diameter cable for the droppers. (In high conductivity, we do just the opposite -- take off or reduce size; often I just tape them up to the ring with electrical tape and keep some of them out of the water). Now, I'm not saying this is a miracle and will create huge benefits, but more surface area in the water will create a slightly more effective field for you.

That's about all that I can offer. I'm sure you know that some of this electrofishing stuff can get really complex. My couple of thoughts are just the simple, practical solutions. I always harp on my students and biologists around here to always take a conductivity reading before starting. It's a key piece of info.

Dave

Dave, how do you take a conductivity reading? Is alkilinity the key? Education time!

With alkalinity at 4 ppm I am surprised there are any fish alive. Sounds like an acid bog.

Dave -- we just carry around a conductivity meter -- very simple. Put a probe in the water, and take a reading. I think the measurement is resistance between a couple of copper lines in the probe. The units are microsiemens/cm, but used to be micromhos/cm before the physicists changed the name. I'm sure it's related to alkalinity/total dissolved solids (I generally don't usually measure alkalinity up here, as we always have "plenty"), as the higher the dissolved solids (the more "stuff"/nutrients/salts/etc.), the more the resistance in the water. So, distilled water is a very poor conductor of electricity. As you add salts (dissolved solids, etc.) then the water can more easily carry some current. So low conductivity is hard to electrofish. If you add a lot of salts, then you get too much resistance, and it's again hard to electrofish because the generator can't supply the needed power against the high resistance. In eastern SD, the lowest water conductivity in which I sample has a conductivty of about 320, and I've "tried" to sample in water over 4,000. I suspect Greg was probably dealing with water that had a conductivity of 10 or even lower, which makes it very hard to get a sample of fish. Electrofishing is most effective (at least theoretically) at a conductivity near that of a fish body. In general, most fish have a conductivity of roughly 150. That's when the most current flows into the fish body, because it's the same as the surrounding water. Well, is that overkill or "education time?"

Dave or Ewest,

Is there any published material out there that suggests settings on the electroshocker unit depending on conductivity readings? Is it true you can overdo it and do major damage to the fish? I do know to much conductivity is just as bad as too little.

Doc, that's just what I needed. Thanks.

CB1 there is such data. Here is an example. Tell me what you are looking for and I will check. Be sure to check the author below.

North American Journal of Fisheries Management
Article: pp. 202–207 |

North American Journal of Fisheries Management 1994

Influence of Water Conductivity on Pulsed AC and Pulsed DC Electrofishing Catch Rates for Largemouth Bass
TRACY D. HILL and DAVID W. WILLIS

Department of Wildlife and Fisheries Sciences, South Dakota State University, Brookings, South Dakota 57007, USA

Abstract.—Electrofishing is a standard tool for sampling largemouth bass Micropterus salmoides, but high water conductivity hampers electrofishing effectiveness. Population estimates (Petersen method) were determined for largemouth bass in 12 small South Dakota impoundments with water conductivities ranging from 410 to 1,700 μS/cm. Even though pulsed DC catch-per-unit-effort (CPUE) values were obtained during the first electrofishing lap at each impoundment, pulsed AC catch rates from immediately following second laps were significantly higher (P = 0.002). The mean number of hours needed to collect 100 stock-length (20 cm) largemouth bass was slightly more than twice as high for pulsed DC as it was for pulsed AC. We developed a multiple-regression model to predict density from pulsed AC CPUE and water conductivity (R2 = 0.88, P = 0.0001). Pulsed AC CPUE contributed 81% to the model and conductivity contributed 7%; both variables had slopes that were significantly different from zero in the two-variable model (pulsed AC CPUE, P = 0.0001; conductivity, P = 0.027). This study suggests that pulsed AC may be more effective than pulsed DC for collecting largemouth bass in waters with moderate (e.g., 500 μS/cm) to high (e.g., 1,700 μS/cm) conductivity, and that pulsed AC CPUE and water conductivity can be used to predict largemouth bass density better than CPUE alone.

Boy, Cecil, that's a tough question! I guess the simplest answer is that it depends on the type of control unit you use. As one example, I've got a Coffelt vvp-15 control unit (now sold by Smith-Root, actually). At 300 conductivity, I can submerge 50% of my electrosphere (we have a round steel ball electrode, rather than a ring with droppers), and I can get about 450 V and 6 amps. That really shocks fish effectively, but doesn't kill them. If I go to another pond with 2500 conductivity, and submerge half the electrosphere, I'll be lucky to get 125 V and it will be at least 10 or more amps (very small, but intense field; not very effective for shocking fish; gotta get the voltage higher). I always think of voltage as size of the field, and amperage as strength (the physicists cringe when I say that! ). So, I raise the electrosphere to 20% submergence, and I can get 240 V and 8 amps, which is a reasonable field. So, I have adapted to my conductivity. If I was at Greg's client's pond, I would submerge 100% of the electrosphere, probably get 500-600 V, and maybe only 1 amp or so. That's why I would shock after dark -- big field, but doesn't hit the fish very hard. Different types/brands of control units operate at different voltages, etc., so my example is not applicable to other types.

The "bible" on electrofishing is probably Chapter 8 in "Fisheries Techniques, second edition." The author is Jim Reynolds, and the chapter title is simply "Electrofishing." The book is available from the American Fisheries Society (www.fisheries.org), although we are more than halfway done with the third edition, and you might want to wait before buying. It will probably be at least 9 months before the new one is available, and maybe longer.

Great book on lots of fisheries "how to and what it means" questions. Check it out here

http://www.fisheries.org/html/publications/catbooks/x55029.shtml

B. R. Murphy and D. W. Willis, editors

Summary
A comprehensive reference volume of modern sampling and data collection methods
in fisheries science for students and professionals. This new edition includes two
new chapters: one on statistical considerations in fisheries sampling and the other
on sampling of invertebrate organisms. All other chapters have been thoroughly rewritten
to include innovations of the last decade. Each chapter provides a description of various
approaches and techniques, with a review of applications, advantages and limitations.
A comprehensive glossary of terms has been added.

First thanks for all the responses. I have read several publications on electrofishing. However lots of physics and not as much pratical experience like Dave as mentioned.

Dave, I do not have a conductiivty meter. I agree it would be good to know but I almost always predict what it would be by looking at clarity and alkalinity (maybe I will get one to have an out). I know if low I have to crank up the volts, dute and rate cycle. Yes you were right on with what I got in Asheville. ABout 580 volts with 1.8 amps with dute set on 85% and rate 100%.

I will try to get a picture on here. I have always in the past worked with two rings. However this time I went with a bar setup with droppers. It did not work well. I increased link of cable to 4 feet (effectively 3.2 feet in water) and now have larger diameter cable and 11 droppers instead of 6. This definently made a diff. It has worked great in higher conducvity water. I use the boat as ground but since it is so big 18.5 feet and 6 feet wide. This means the amount of the anode needs to be large as well. It is a control box made by Univ. of Wisc. With a 8500 watt genetrator.

SO yes I think ading more surface area is what I ned to do. However I plan to rewire and now have power to both booms and two rings. So Dave I guess no harm in having longer droppers than rings in the past except exess weight. I will try to get a pic on here of the system to see if I can get more free advice.

Ewest actually alkalinty less than 4 is quite common around here.

Wow, big generator, Greg! 8500 W ought to really help when struggling with the low conductivity.

Greg, you could get a conductivity meter and ask the client to send a water sample, so you will know the results to expect. Look for a DIST WP3 tester. It is from 10 to 1990 micro mhos or micro siemens. They are only about $60. You just put it in the water and hold a spring loaded button down for reading. It is very accurate. We use it for mixing up ship gyroscope fluid where the gyro sphere is floating in liquid and the motors get current thru the liquid. Not sure where it was purchased, but saw on on line from Canada for 89 CAD.

here is another one.

http://www.bestlabdeals.com/category_s/1062.htm

BM thanks for that info. I alwyas that they were more than that, for that price I will get one ordered right away.

Dave you would think I could shock fish a mile away with that sucker but not if clear. We will get it working and thanks for your help.

This is Greg's.

Thanks Bruce, so Dave this is before I changed the cables to larger diameter and befoe I added a total of 11 droppers, any other ideas? Like I said I plan to have the two ring system employed once I'm out of commission when the baby arrrives.

Notice how Greg leads by example for his employee.

He makes the employee wear a life preserver, yet he does not.

Awesome. Good risk management technique!!

No Greg, I don't have any other good recommendations. More droppers and shock at night in clear, low conductivity water. I haven't looked specifically at electrode configurations and electrical fields, but I've used "dropper bar" boats like yours before, and they worked just fine. Not sure if the Wisconin rings will make any difference, actually. I remembered a couple of good low conductivity stories. We were shocking the Colorado River in central Colorado using a generator and control unit on shore. Conductivity was low, and we had lots of volts but no amps. Our ground was a cable that we laid in the water near the generator. Well, it had a clip on the end, and I clipped it onto some car bodies on an outside bend of the river. That did the trick! All of a sudden, I could read some amperage. In smaller Colorado streams, we actually used the old trick of carrying a salt block (cattle supplement). When we hit a stream with extremely low conductivity, we would put the salt block in the riffle above, and that put enough ions in the water to let us shock successfully. Amazing, actually.

SUnil yep I hope my liability insurance and workers comp. company does not see that pic. ALso notice that is how I spent most of my days on the Da_n cell phone. I will post if we make a diff and appreciate the help.

i hope you boys are doing well...long time no post!!

baby is now 21 months old...and mama's letting me do some pond stuff again!!

i'm planning on shocking my pond june 9th at 10am. the local fisheries guys are doing it.

what should i be prepared for? the pond has not been shocked before, and i have been to busy to do a lot with it this past year. lots of small bass, so needs culled i'm pretty sure.

the blue gill would make bruce's mouth water (and no assistant around to suck that stuff out bruce....it would just dribble down that chin!!)

so, what should i expect? coolers with ice?

i'll take a camera and post some pics hopefully after we are done.

oh, and how many watts are those generators on typical pond shocking boats?

mark

Mark the useful part of shcoking is unbiased sample (not exactly true) but best tool we have. You will gets lots of small bass for culling if that is what you have. However some folks think you get all the fish not so and not even more than 30% in most cases. However great tool. Make sure you hvae a clear goal in mind. If bass then do not takeout any bluegill including the big ones. I think you know why. Good luck and let us know what you findout. My baby is supposed to be here today but I think she is a couple of days away still.

Mark!! Glad you're back! My assistants would love the chance to work on me when I'm numb....Payback for all they have to put up with.

hey boys...glad to be back. i'm so excited about shocking the pond tomorrow and can not go to sleep (plus i'm on call and that dang pager won't shut up!!) i'm really excited. i've got some friends coming over with coolers, because i have to head back to work after part of the shocking is done. i plan to cull out the small bass...i think it is over loaded with small bass. will let you know how it goes...gonna take some video.

greg, congrats. please email me some pics. your life is about to change, it is wooonnnddderrrfulll. i took my little girl for a jet ski ride (slow of course) and watched the sunset just a few hours ago. precious. she fell asleep in my lap as we watched the sunset. you are gonna love it!! congrats again. mark

mark

Greg G., are you a father now? If so, congrats!!

Name, weights, lengths???