Bladderwort/Grass Carp Q&A

What is Bladderwort?  Bladderwort is a rootless, free-floating aquatic plant that is sometimes noticeable by its small, yellow flower protruding from the surface of the water. The species is called Bladderwort because of its inherent bladder-like structures connected to the submerged segments of the plant. The plant is carnivorous and uses these bladders to capture tiny, aquatic organisms such as insect larvae, aquatic worms, water fleas, etc.

Why is Spartanburg Water managing Bladderwort? Bladderwort can be a nuisance aquatic plant by filling in coves and attaching to boat motors, affecting navigation and recreation. More importantly, it can potentially impact the long-term sustainability of our drinking water and subsequent treatment efforts.  However, despite its reputation as an invasive plant, Bladderwort is not harmful to the lake, its wildlife or those who live on the lake. The plant itself is a completely normal and viable part of freshwater lakes. It helps filter pollutants and is an indicator of good water quality, but we recognize this is an instance of having too much of a good thing.

What is a grass carp?  A Grass Carp, or White Amur, is a vegetarian fish native to the Amur River in Asia. The U. S. Fish and Wildlife Service introduced grass carp into the United States in 1963 for experimental purposes. Because this fish feeds on aquatic plants, it can be an effective biological tool for control of nuisance vegetation or algae. This particular species of carp has been genetically engineered to be sterile. As a result, the carp is also referred to as a Triploid Grass Carp.

Why are grass carp being added to Lake Bowen & Municipal Reservoir #1? Triploid Grass Carp are used around the world and are one of the approved methods being used by the South Carolina Department of Natural Resources to control invasive and nuisance weeds and algae. Spartanburg Water has successfully treated Bladderwort in Lake Bowen in the past using this method and will restock the lake as maintenance. Spartanburg Water will use the same, proven strategy to help control the growth of Bladderwort observed in Municipal Reservoir #1.

Where are grass carp being added in Municipal Reservoir #1?  Spartanburg Water has used sonar equipment to monitor and map out the areas most affected since discovering Bladderwort in Municipal Reservoir #1 in 2016. Based in part on the data collected, Spartanburg Water will target the growing areas impacted by Bladderwort.

How many grass carp will be stocked in Municipal Reservoir #1 & Lake Bowen?  The plan calls for 1,750 Triploid Grass Carp to be stocked in Municipal Reservoir #1 as an initial, original stocking and 400 Triploid Grass Carp to be stocked in Lake Bowen as a “maintenance stocking.”

How long will carp effectively reduce algae and weeds?  When water temperatures are cold, (below 50-55 degrees), grass carp eat very little.  When they are 6 years or older, their metabolism slows and they also eat less than normal. However, during warm conditions and from the ages of 1-5 years old, grass carp can eat up to 6-10 percent of their body weight each day.

How long will the grass carp live? Ten years on average. 

Will grass carp dominate or disrupt the ecology of current populations of aquatic wildlife?  No. The grass carp is a sterile species and therefore cannot reproduce.  Also, grass carp feed primarily on plants and algae and do not consume other fish.

How can I tell the difference between common carp and the stocked triploid grass carp?  The major difference when looking at the carp from below is the length of the dorsal fin. The triploid grass carp has a significantly shorter fin than the common carp.  There are other more subtle differences, the most easily identified of which is the presence or absence of barbels around the mouth.

Is it illegal to catch triploid grass carp that have been stocked in public waters? Am I able to fish for grass carp?  Please remember, it is illegal to “take” triploid grass carp from public waters according to section 50-13-1630(D) of the S.C. Code of Laws.  If you hook a triploid grass carp while fishing in public waters, please release it back into the same water body.  If you take a triploid carp, you are subject to penalties prescribed by law.

Will grass carp control the Bladderwort problem?  Triploid Grass Carp are a good alternative management strategy to conventional methods such as copper sulfate. This practice has been adopted by the South Carolina Department of Natural Resources as the current recommended strategy for mitigating certain aquatic invasive plant problems in South Carolina.

If the reservoirs stay at full pool, will there be a reemergence of Bladderwort?  Bladderwort is an annual plant that typically thrives in low-level, high-temperature conditions such as coves.  With full pool conditions and regular rain events, Bladderwort is less likely to appear in large numbers.

How will Spartanburg Water be informing stakeholders regarding the project?  For your convenience, Spartanburg Water will be installing informational signs at each landing and public fishing area prior to the start of the project. We will also post updates on our website, as well as in our bi-monthly Healthy Lakes newsletter.  You can also sign up to receive lake alerts here.  Should you have any additional questions regarding the project, please contact the Lake Bowen Wardens’ Office by phone at (864) 592-2240 or by email at

How can I help?  There is a way you as homeowners and stewards of the lake can help Spartanburg Water.  You may have noticed populations of Bladderwort that have migrated by wind along the shoreline.  It is very difficult for Spartanburg Water to access the entire shoreline at each potentially affected residence.  For lakes such as Lake Bowen where recreation is allowed, we encourage the use of clean boat hygiene practices: Boats should be inspected for plant fragments before launching in the water and after boats have been removed from the water.