Brian Triplett: Ag Biz

Let me ask you a question: how happy are you with your pond?

If you are managing your pond for recreational fishing, are you filled with excitement when you pull a typical fish out of the water or deflated with disappointment? Nothing can ruin the fishing in a pond faster than the introduction of undesirable fish such as bullhead catfish or a stunted population of game fish such as largemouth bass.

While correcting an imbalance in the population characteristics of desirable fish can be accomplished with time, dedication and patience, removing the entire population of an undesirable rough fish — carp, bullhead catfish, gar — can be difficult at best without the use of the proper tools. We’ll save the topic of correcting population imbalances in desirable fish for a future column and more comfortable time of the year.

If you want to start the fish population of a pond over, there is no time like the present. Hot weather will assist you in your renovation task, and with temperatures flirting with triple digits lately, conditions could not get much better than this to use Rotenone to renovate a pond.

Rotenone, a naturally occurring compound found in many plants, kills fish by interfering with oxygen exchange in the gills and causing suffocation. Fish killed by Rotenone are not suitable for human consumption. Water treated with Rotenone should not be used to irrigate crops. Rotenone is a restricted-use pisciside (fish killing pesticide) in Texas and is only labeled for sale or use by individuals with a Texas Department of Agriculture pesticide applicator’s license. Most products used for fish control will be 5 percent powder or liquids and should be used when the pond water temperature is greater than 70 degrees.

The trick for completely eliminating all fish is to accurately determine the volume of water in a pond. An accurate estimate of the acre-feet of water in your pond will be needed or you risk one of two events occurring. You underestimate the volume of water, under-apply the amount of Rotenone needed and get an incomplete fish kill. Or you overestimate the volume of water, over apply the amount of Rotenone needed and spend more money than necessary to complete the job.

If the pond has a drain pipe you can lower the pond’s water level prior to treatment, which will decrease the volume of water and amount of chemical needed. If you do not have a drain pipe, you could use a large diameter hose (like a fire hose) to create a siphon and lower the water level. If you plan to lower the water level prior to treatment, lower it before calculating the pond’s water volume.

Accurately estimating the water volume takes some time. The first step will be to estimate the average depth of the pond. This can be accomplished with the use of a weighted line or lightweight pole marked in one foot increments. For best results, you will want to measure depth in as many places as possible.

If you have a rectangular shaped pond, start on the long side of the pond, taking and recording measurements every 10 to 20 feet until you reach the other shore. Repeat this process on the short side. Add a measurement of zero feet when you begin and end each side. Total the depth measurements and divide by the number of measurements taken. This figure should provide you with average depth.

Determining pond surface area is a little simpler. If you have a square or rectangular shaped pond, it is length times width. Triangular or circular shaped ponds require a little more complex math.

Once you have the average depth and surface area you can calculate water volume in acre-feet.

Follow the product label for the amount of product to use in your pond, how it should be applied, and what type of personal protective equipment you should wear during the application.

For more information on using Rotenone and calculating the volume of water in a pond, please visit the entry posted at http://agrilifeblogs.tamu.edu/mt/smith.

Brian Triplett
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