Chris Bridges
Rural communities throughout the country are blessed with abundant opportunities for fishing in small lakes and farm ponds. Despite the great fishing and hunting experiences that these waterbodies provide, farm ponds may be one of the most overlooked landscape features when it comes to monitoring and planning for effective habitat stewardship. However, by understanding the basic chemical and biological functions of these unique ecosystems, fish habitat can be improved and we can improve the quality of outdoor experiences that these ponds provide for our family and friends.
Why Should I Care About Pond Chemistry?
First off, I think that it is important to understand why we should monitor the pH, nutrient levels and dissolved oxygen of ponds. For my purposes, I typically use the term farm pond to describe water bodies that are less than ten acres. Obviously, there are many natural lakes in many parts of the country whose fish communities have evolved together. Farm ponds are different in that the vast majority were constructed in the last two hundred years. Additionally, these ponds were likely constructed for a variety of purposes ranging from livestock water supply to soil erosion, sediment control and flood risk reduction. Recreational fishing opportunities were sometimes not the primary reason for constructing farm ponds, but with a little understanding of how to manage the chemistry, these waterbodies can certainly provide landowners with multiple benefits.
Farm ponds also represent a type of system in which the inputs and outputs can be more readily measured than other types of habitat. Because we can readily account for the streams that feed the pond and the outflow that leaves the spillway, we should be able to manage the water to have the ideal concentrations of nutrients and dissolved oxygen that will support bass, catfish, bluegill or whatever type of fishery you want to develop. I have found it useful to inventory the watershed, or the area that drains into your pond, to determine the relative percentages of forest, pasture or cropland that drains into it. This will have major implications for how much annual fertilizer and lime likely finds its way into the pond.
How to Check Your Pond Chemistry?
There are a variety of kits available that landowners can purchase to measure pH, dissolved oxygen and nutrient levels. One of the most obvious ways to examine the quality of water in your pond is a simple visual assessment. However, land managers must be thoughtful in their monitoring. Many folks managing farm ponds seem to prioritize water clarity over biological productivity. What I mean by that is that having water that is crystal clear might be aesthetically pleasing, but might not contain the algae and zooplankton that make up the base of the pond food chain. There are many chemical products that folks use to control algae growth, thereby improving the clarity of the water. Obviously, clear ponds will likely have less algae growth and subsequently less food for lower level consumers in the pond, potentially influencing the growth of higher level consumers like bass, bluegill and catfish.
A simple, low cost way to test clarity is to lower something into the water column and measure how far down it is visible. Pond managers and fish biologists often use a simple instrument called a Secchi disk, which is just a black and white circle that is lowered into the water by rope. When it is no longer visible, the observer records the length of rope as a means of measuring water clarity. As a substitute for a Secchi disk, I have used yardsticks or rulers attached to black and white tape to attain the same type of estimate. In the Midsouth, many pond managers will aim for water clarity of 1.5 to 2 ft. Water that is too clear may indicate low nutrient levels and water that is less clear might be a sign of turbidity resulting from clay particles in suspension, livestock access or excessive algae growth due to high nutrient levels.
In order to determine the actual cause of water clarity problems, chemical analysis of the pond can be helpful. There are many private consultants who can assist, or there are many laboratories that can examine water samples obtained by pond owners. I would just remember that the results are only as good as the sample, so I try to obtain the sample from the area of the pond that I am trying to manage for fish production rather than the most convenient place to pull the sample. I discuss sampling containers with the selected laboratory and typically mail the sample off for analysis.
How Can I Use This Information?
The results of your own observations of clarity, in addition to chemical analysis of pond nutrients, pH and dissolved oxygen can all be used to develop an effective plan for fish habitat improvement. Low nutrient levels might suggest a need for additional nitrogen and phosphorus. Because colder water holds more dissolved oxygen than warmer water, low dissolved oxygen might be improved over the long term by the addition of trees for shading or more quickly by the installation of an aerator. Finally, low pH of a pond can be improved by the addition of lime. While I have encountered many more ponds in the South that are acidic than basic, it often requires chemical analysis to determine the pH and alkalinity to know rates of lime that will be effective in improving fish habitat. Most pond managers in the Midsouth aim for pH levels of >6.5 and dissolved oxygen levels between 5 and 9 ppm. These measurements will vary depending upon the flow into and out of your pond, the tree cover around the banks and many features of the landscape that drains into your pond.
Farm ponds are complicated ecosystems that can provide a wide range of benefits for families and communities. They play important roles in storing flood water, processing nutrients and providing fish and wildlife habitat. Chemical and physical assessment of ponds can help managers to better understand these systems and the biological processes that farm ponds are undergoing throughout the year. Sampling and maintaining records is important to detect both short and long term trends in water chemistry. By better understanding the chemistry and biology of farm ponds, we can improve the fishing opportunities that these waterbodies can provide for our families and friends.
Check out the Gamekeeper Podcast topic on this very subject:
