Grass Carp – Miracle Fish Or Unwanted Exotic Pest?
As a responsible lake management company, we are tasked with managing lakes and storm water ponds in a manner that is not only cost effective and beneficial for the customer, but also environmentally friendly and ecologically balanced for the specific ecosystem in question. As such, we often implement strategies that are multi-faceted, utilizing the benefits of many tools in combination to get the job done. Ecological balance is rarely obtained by utilizing only one methodology, and without balance, there are rarely good results.
“Biological controls” come in many forms, and refers to the use of natural or biological introductions to a given water body to help achieve a desired management objective. Triploid (sterile) Grass Carp (white amur) are often used by lake owners and managers alike to help control unwanted aquatic vegetation, due to their ferocious appetite for vascular plants growing in or around a lake. These fish are regulated by the VA Dept of Game & Inland Fisheries, and a permit is required in order to have them stocked in your lake or pond. They are also required to be sterile, so that they do not over produce and potentially cause harm to lakes and down stream waters by over eating and destroying the beneficial wetland and aquatic plants that are a vital part of our waterways.
So, what is a pond owner or lake manager to do if they wish to promote biological solutions to their lake problems and minimize the amounts of algaecides and herbicides applied to their water? Should they stock sterile grass carp? The answer is far from simple…As environmental stewards, we seek to avoid the introduction of exotic plants, fish, or any aquatic life that is non-native and not indigenous to our area, as that will typically upset Mother Nature’s balance and cause unintended consequences down the road. Grass carp are not native to North America, so we have to be careful if we decide to use them as a management tool. The fact that they are sterilized at the time they are grown is a step in the right direction, but other measures need to be considered.
First, do not over stock. A lake or pond is not supposed to be a “bathtub”, baron of all forms of vegetation. 20-30% coverage of native aquatic and wetland plants is needed for a healthy and balanced pond. Beneficial shoreline vegetation along with some of the native submersed species should be supported and allowed to prosper. Therefore, if using grass carp to control unwanted aquatic weeds and vegetation, you should only stock enough to eat a particular quantity of plants per day, but not enough to wipe out all of the plants that inhabit the pond.
Second, if your pond has an outflow device that would allow the fish to escape during heavy flow after significant rain events, then you should install a screening structure in front of that outflow to prevent the fish from swimming down stream. The grass carp are drawn to fast moving / flowing water, and would likely leave the pond at the first chance if conditions were right. Not only would you have wasted your money and efforts if the fish escape, you will have also created the potential for down stream destruction of valuable aquatic habitats, something that must be prevented at all costs.
Finally, grass carp are primarily bottom feeders. As such, they have a tendency to stir up the sediment on the bottom. Often times in shallow ponds, this results in excessive turbidity (cloudy, dirty, brown looking water). Even if they eat all of your unwanted weeds, if you end up with a dirty looking pond all the time, all you have done is replace one problem with another.
There are many other things to consider when stocking fish of all types. When managing a lake, these and all other parameters should be considered while formulating a long term plan. A little education and foresight goes a long way towards achieving the desired results and overall satisfaction, while minimizing unwanted environmental impacts.
SOLitude Lake Management has been committed to providing full service lake and pond management services that improve water quality, preserve natural resources, and reduce our environmental footprint. Services are available throughout the Eastern United States. Fisheries management consulting and aquatic products are available nationwide. Learn more about SOLitude Lake Management and purchase products at www.solitudelakemanagement.com.