Lake Fertilization: A Tool to Better Lake Productivity

By Mike Gore, Fisheries Technician

There are times a lake needs a little help to become a productive fishery. One method utilized by fisheries biologists is lake fertilization. As you may know, nature’s creatures are all part of a food web. Sometimes in our lakes, or ponds, part of that web is lacking in productivity, therefore making other parts of the web lacking in productivity, too. In the case of our water systems, the food web is made up of phytoplankton, zooplankton, aquatic insects, juvenile fish, and adult fish. Phytoplankton are microscopic plants in the water column. The presence of phytoplankton is usually indicated by the greenish tint in the water, made up of such things as diatoms and dinoflagellates. Zooplankton are the microscopic animals in water, examples of which are creatures known as copepods and rotifers. The juvenile fish rely on these forms of plankton to survive to become bigger fish, therefore providing a wide variety of different sized fish that will be utilized as prey for the growing adult fish, and so the food web continues on until the fish become catchable size for anglers to enjoy catching and releasing, or harvesting for a meal.

We recently had the opportunity to help one of our lakes become a more productive fishery with the use of fertilization. We introduced 800 gallons of fertilizer into the lake via a chemical spray pump, and hose injecting the fertilizer into the water from an airboat. Lake Bryan in Bryan, Texas an 829 acre power plant lake owned by Bryan Texas Utilities (BTU), is mostly utilized by locals for watersports, i.e. jet skiing, and sailing, etc. There are anglers that utilize the lake, too, mainly to fish for crappie, and catfish. Bass are present in the lake, but difficult to catch because of the lack of vegetation. For years, one of the main problems with the lake has been productivity. Fish growth is very slow due to the lack of lake nutrition, i.e. phytoplankton and zooplankton. We have seen 2 year old fish that are only 8 to 10 inches long. We recently, had a 5 pound fish that was aged at 13 years old. In a lake with a good forage base, the weight of a fish that old would be higher. Also, complicating the issue is the turbidity of the water, due to suspended clay particles, and several species of algae. These factors make it hard for the lake to support vegetation, specifically underwater vegetation. Some of the vegetation present in the lake are emergent species, such as cattails, and rushes. These are nice to have, but grow primarily in shallow water along the edges of the lake. Ideally, a more diverse vegetation community is desired, with some plants growing in deeper water to provide more cover, providing nursery areas for young fish, and more habitat for fish to live in general. This diverse habitat would help with providing a healthy environment for the plankton species to grow, and thrive. We are in the early stages of working with BTU to help change the health of the lake, and know what the results of our work will be, but cooperation between entities is the first step in successful management of a resource.

These same principles are used in small pond management. For example, if you have a pond in which the fish are just not growing as big as they should be, and you have a clear pond where you can see deeper than 24 inches, you may need to fertilize your pond to create a plankton bloom, which is indicated by the water turning green because of the increase in phytoplankton. This hopefully induces an increase in productivity of your pond. Of course, diagnosing the exact issue would take more diligent investigation, but there are certain things you can look for to narrow down a waterbody’s issues.

Fertilization of a waterbody is just another tool we use to make a better fishery. We strive every day to do all we can to help our lakes be as productive as they can be for our constituents, and we hope you go out and enjoy the resources our great state has to offer. So, go out, make some memories, take a kid fishing, and we’ll see you out on the water!

If you have any questions please contact us at (979) 272-1430 or by email at mike.gore@tpwd.texas.gov or mark.webb @tpwd.texas.gov . Also, visit us on Facebook at https://facebook.com/TPWInlandFisheriesCollegeStationHouston.