The Good and Bad of Aquatic Vegetation Management
By: Justin Bryan
Rarely does a single day pass that I don’t talk about aquatic vegetation management with a lake or land owner that is disappointed with lack of “fishability” of his water. Typically, the conversation begins with how to identifying the plant followed by answering the question of how to get rid of it quickly. But before we dive deep into controlling weeds, let’s first talk about why the plants grow in the ponds and lakes. Fully understanding aquatic vegetation can lead to successful aquatic vegetation management and control.
In the early spring plants will grow first in sunlight rich shallow water with a depth of 3 foot or less. Algae species are the first to grow because they are single celled and very opportunistic. They can be floating, attached to other plants or structures, and they can even grow in a manner that mimics rooted plants. Shortly after the algae establishes then both, submerged and emergent plants begin to outcompete it.
Submerged & Emergent Plants
These plants have more complex cell structures and defined roots. Their ability to absorb nutrient from both the soil and the water column means they will outcompete phytoplankton (microscopic marine plants) for nutrients. As phytoplankton density is reduced water will become excessively clear…which is aesthetically pleasing but bad for a fishery. This is a very important concept to grasp for aquatic vegetation management. As clarity increases sunlight will allow aquatic plants to grow in water depths of 8, 12, 15 or even 20 feet.
The nutrients in runoff water, fish food, waste, fertilizer, and decomposition of every plant and animal in the waterbody will further feed the growth of the vegetation. To complicate things even more, most aquatic plants will reproduce in multiple ways; seeds, rhizomes, and fragmentation are all ways for many submerged plants spread. This all means aquatic plants grow rapidly and if uncontrolled due to a lack of a aquatic vegetation management plan, they will become detrimental to your fishery.
Aquatic Vegetation Management Step 1: Identify if the Vegetation is Good or Bad
Once you understand why plants grow you can then begin to put together an aquatic vegetation management plan. The first step to controlling any plant is to identify what specie or species you have. Many aquatic plants look similar so visual aids, websites, and many times professionals are needed to identify the plant correctly. Once identified, you can learn how quickly it grows, at what depths, how dense and what the best control method is likely to be. A slow growing, shallow water loving, thin plant is preferred over something that doubles in size quickly, grows in twenty feet of water, and looks like knotted twine. These preferred plants will need a less aggressive aquatic vegetation management strategy over non preferred plants and of course be beneficial to the fishery.
Aquatic Vegetation Management Step 2: Control Methods
If controlling the plant is necessary, accurate identification is once again important. Each control method will have benefits and detriments. We classify control methods as chemical, biological, and mechanical. Each method targets the control and removal of the plant differently.
- Chemical – Chemicals such as herbicides and algaecides act by attacking cells or specific plant structures. They can be used to control a specific plant in a small area or to target multiple species in large areas. Unfortunately, selecting the wrong chemical or misusing it will result in negative effects such as fish loss.
- Biological – Biological control is the use of a living organism to consume the unwanted plant. Various species are available to use depending on the plant you have and the state you are located in. Each species will have specific plant preferences, environmental requirements, lifespan, and reproductive habits.
- Mechanical – Mechanical control, such as cutting and raking can be effective in small areas on specific plants but it is labor intense and a short term solution.
Aquatic vegetation management is critical knowledge to have for land management and land ownership. Whether it is keeping a water source such as a lake or pond aesthetically pleasing or keeping a fishery intact, implementation of an aquatic vegetation management plan should be on your radar.
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