Silver Carp Report


Timothy Joseph, PhD

Fishery Biologist

Executive Summary by

Mary Anne Koltowich
Roane County Environmental Review Board

This report provides valuable information regarding the Silver Carp Threat to Watts Bar Lake and the Tennessee River System. It presents the history of how Asian Carp were introduced into the United States (U.S.), biology of the Silver Carp species, range of where the Silver Carp are found in the U.S. and the Tennessee River system, ecological impacts caused by the species, recreational impacts of participating in water sports, economic impacts to tourism and properties, methods to prevent of migration, current efforts to prevent the spread of Silver Carp, costs to construct barriers, what must be done in the very near future, the vital nature of timing to take action, and specific recommendations to the Roane County Commission to help stop them from devastating Roane Counties most valuable environmental, recreational and economic natural resource.

Silver, and other Asian Carp were introduced for various aquaculture purposes in the 1970s. They were confined in production ponds, but unintentionally introduced into natural waterways during extreme floods on the Mississippi River. Most biologists were against such introductions for they understood that a natural ecosystem should never be altered and knew it would be difficult, if not impossible, to ensure their confinement.
The species occupies a major portion of the Mississippi River drainage basin, is present in the lakes and rivers of the Cumberland River in Middle Tennessee, and is known to be present in the Tennessee River system from the confluence from the Ohio to the Wheeler Reservoir in Alabama. They may be present at the Guntersville lock and dam.

Silver Carp can live 20 or more years, can grow to over four feet in length and weigh 75 pounds. They reproduce rapidly and will devastate an ecosystem. A mature female can lay 4-5 million eggs each year. Due to this ability to rapidly reproduce, they quickly take over and outcompete native fish species causing enormous damage to the entire ecosystem. They consume the bottom of the aquatic food web (phytoplankton/algae and zooplankton) which is responsible for the health of the entire ecosystem, including all native forage and game fish.
Recreation is impacted in a major way. When Silver Carp are startled by a passing watercraft they panic and jump out of the water as high as six (6) to ten (10) feet. This behavior makes waterskiing, wakeboarding, jet skiing, tubing, fishing, and boating extremely dangerous and has resulted in serious bodily injury (broken jaw and fractured skull).

Economic impacts include major tourism revenue losses to the state, counties, cities, marinas, and many other small businesses. Fishing tournaments may all but disappear. Property values will drop significantly, along with property tax revenues. These losses can amount to hundreds of millions of dollars each and every year.
To prevent migration of these fish upstream, electric barriers, a proven technology, have been installed in many locations nationally and internationally, and have been in use since the 1950s. These electric barriers are installed in locks to prevent the fish from entering the lock. No permanent injury to the fish is caused, and there is no danger of electrocution to people. Bio-Acoustic Fish Fences (BAFF) is another technology, but not yet proven to adequately deter Silver Carp.
Millions of dollars are being spent in Kentucky to try and gain some control, even subsidizing commercial fishing of Silver Carp to reduce their numbers. However, harvesting alone will not significantly reduce their numbers due to their extremely high rate of reproduction. Money must be spent on the installation of barriers rather than further research.

The estimated cost to install an electric barrier on a typical Tennessee Valley Authority (TVA) lock is $10 million. However, one must take into account that the Tennessee River brings in $12 billion annually and local economies average $1 million of income per mile of shoreline. Funds can be raised in a number of ways.
It is concluded that electric barriers need to be installed as soon as possible at the Nickajack and Chickamauga locks. Once complete, electric barriers then need to be installed at the Watts Bar lock. These efforts need to be undertaken by the Tennessee Wildlife Resources Agency (TWRA), U.S. Corps of Engineers (COE), and TVA working together to design and construct these barriers.

Time is critical. The Silver Carp are present in Wheeler Lake and may have entered Guntersville Lake. The ecology of our lakes is under attack, and billions of dollars of revenue to the region are at risk of being lost. It is vital to make funding available to prevent the ecological, recreational, and economic losses that will occur in the near future if the Silver Carp reach a lake.

Recommendations for the Roane County Commission are given in this report. One is to establish a committee group to include involvement from counties on the Tennessee River from Chattanooga to Oak Ridge. It calls for a joint six-county resolution to the Governor of Tennessee asking for the establishment of a joint TWRA, COE, and TVA task force to take actions. Public education workshops should be conducted for the six affected and named counties.

Silver Carp: Hypophthalmichthys molitrix


In the 1970s nearsighted state biologists, natural resource managers, sewage treatment facility operators, and others made appalling errors in judgement by thinking introducing nonnative species would be a good thing. Those decisions resulted in dreadful and devastating ecological consequences we face today, both in the terrestrial environment (Kudzu) and aquatic ecosystems (Asian Carp). Most biologists were against such introductions for they knew it would be very difficult, if not impossible, to ensure none were ever released into the natural environment. As well, they stood by their belief that a natural ecosystem should never be altered by changing the species diversity. Simply put, nothing can improve on a natural ecosystem. Yet nonnative invasive species still were imported.

Nonnative organisms often have a devastating impact on natural resources, human health, and the economy. In a natural ecosystem, organisms evolve together into a native community with checks and balances that determine population growth and species diversity. A complex web of interactions is established by primary producers, predators, herbivores, bacteria/disease, parasites, and a multitude of other organisms forming an important and complex ecological balance. An introduced species will not have the evolutionary barriers or limits, and their populations can explode, disrupting the natural communities and ecological process. They can outcompete and even eliminate native organisms making the ecosystem less diverse which leaves it even more susceptible to further devastation including disease, habitat alteration, and critical habitat elimination.

Introduction of the Asian Carp is one of those grievous decisions that has had devastating consequences. There are four species now in the United States (Grass, Bighead, Silver and Black), all from China. They were introduced for various aquaculture purposes, then escaped from confined production ponds and unintentionally introduced into natural waterways during extreme floods on the Mississippi River. Their relentless invasion quickly increased their distribution and abundance. All four Asian carp species are now abundant in the Mississippi River Basin and have migrated into Tennessee waters via locks at Kentucky and Barkley dams and have entered Reelfoot Lake during high flows through its spillway. For the purposes of this report, discussion focuses on the silver carp, as it is the one representing the imminent danger to Watts Bar Lake, nearby lakes, and the Tennessee River system.


The Silver Carp has a deeply keeled body with tiny scales but no scales on the head or gill covers. They mature in 2-3 years and can live 20 years or more. They have a large mouth with no teeth in the jaw, with eyes forward and turned slightly downward. They can grow to over 4 feet in length and weigh75 lbs. They rapidly reproduce and devastate an ecosystem due primarily to two factors which give them a great advantage. First, a large mature female can lay 4-5 million eggs each year. Secondly, they do not require nesting habitat as most fish do; they spawn in the water column. The slow current keeps the eggs suspended until they hatch and begin feeding.

Silver Carp are planktivorous filter feeders, meaning they merely swim with their mouths open and consume whatever is floating in the water column, primarily phytoplankton and zooplankton. They can filter out 20-40% of their body weight each day which represents millions of planktonic organisms. They are so efficient they have been used in sewage treatment ponds to reduce and remove algal blooms.

The Silver Carp is considered by many to be a fine food fish due to its good flavor, texture, and appearance. Live fish can even be found is some high-end food stores. Because it feeds only on plankton and not benthic organisms or other fish, the flesh is free of toxins like PCBs and Mercury when these toxins are present in the environment. Commercial fishing for this fish is being done is some states as a measure to reduce their numbers and is highly recommended and sponsored by the State of Tennessee.

The abundance of Asian carp has attracted more commercial fishing. This can remove millions of pounds of carp annually. At the recommendation of the Tennessee General Assembly’s Asian Carp Task Force, the Tennessee Wildlife Resources Agency (TWRA) funded a $75,000 grant in 2017 to the Paris Henry County Industrial Committee to develop local commercial fishing businesses for carp. As a result, recipient businesses have increased their interest in harvest of carp. TWRA is currently drafting another plan to provide even more incentives to commercial fishers and wholesale fish dealers. During May of 2018 the Tennessee Fish and Wildlife Commission approved a $500,000 budget request to provide incentives for the commercial harvest of these fish in Kentucky, Barkley, Cheatham, and Old Hickory Lakes.



Figure-2 below shows the distribution within the U.S. A major portion of the Mississippi River drainage basin has been taken over. Silver Carp are making their way upstream and will take over the entire Tennessee River ecosystem and its tributaries unless a major effort to prevent migration is implemented at Tennessee River locks “Immediately.” Time is the best friend of the Silver Carp and the worst enemy of the TVA system of lakes and reservoirs.




The figure above shows the distribution in Tennessee, but it is likely to be out of date. The fish will effectively move upstream to every river system and tributary unless there is a dam with a lock. Without effective control measures, nearly the entire map above will be red.

Figure 4: Alabama Presence of Silver Carp

Figure-4 shows where Silver Carp have been found and captured in the Alabama portion of the TVA system of reservoirs. What is unknown is the population abundance. Their mere presence in Wheeler Reservoir indicates they are very likely present throughout the lake and could very well be at the Guntersville lock and dam. If indeed they are at the lock, they will quickly enter Guntersville Lake.



Due to the extremely high fecundity (up to 5 million eggs/mature individual), Silver Carp can quickly take over and outcompete native species causing enormous damage to the entire ecosystem. There is abundant literature showing that their numbers alone will quickly alter the trophic levels of the native fish communities. This is due to the extreme number of individuals each consuming up 10-40% of their body weight in phytoplankton and zooplankton every day. This can quickly reduce the food availability for juvenile fish, forage fish, native filter-feeding fish (shad), mussels, insects, and other organisms that completely rely on phytoplankton and zooplankton as their only food source.

Carrying capacity refers to the maximum population size of a species that the aquatic ecosystem can sustain indefinitely and is based on the food, habitat, water quality and other requirements available in the environment. In a balanced system all species are below, near, or at carrying capacity and doing well. The phytoplankton and zooplankton are the primary producers, the bottom of the food-pyramid, and represent the food source for juvenile fish and the wealth of benthic fauna which are also a major food source. Altering the bottom of the food-pyramid will quickly change the biodiversity of the ecosystem. This is a devastating ecological impact, for the entire ecosystem is out of balance. When the bottom of the aquatic food-web is severely reduced, it can quickly result in the loss of native forage fish and game fish due to lack of abundant food sources and the resulting stress. This will eventually lead to a lake so out of balance, that for all practical purposes, it would be a fisheries monocultureof Silver Carp. Other fish species would struggle to maintain presence, but their numbers would be low,highly stressed, leading ultimately to possible elimination of species from the ecosystem.

It is critical to restate the vital importance for what is the foundation of a healthy aquatic ecosystem, the primary producers at the bottom of the food-web. Every living organism in the ecosystem is tied to the health of that foundation and cannot survive long without them. The Silver Carp feeds ravenously on that very foundation, and their ability to multiply in extremely high numbers can quickly overwhelm and destroy that foundation. By devastating the population of phytoplankton and zooplankton in a lake, they are destroying the food source for all other organisms. As they continue to devour the plankton, even the Silver Carp population itself will become stressed, for their carrying capacity also depends on the abundance of phytoplankton and zooplankton which they are rapidly destroying. They will reach and exceed their carrying capacity which will lead to fish-kills/die-off of the Silver Carp. Silver Carp are the cancer cells of an aquatic ecosystem. Just like cancer cells in the human body, the fish multiply until they kill the host and thus themselves.

An unbalanced aquatic ecosystem will never completely recover. The remaining fish would continue to repopulate to their carrying capacity at the expense of all other organisms, this maintaining the imbalance year after year. Their relentless attack on the primary producers in the food-web could never be stopped except by completely eliminating the Silver Carp, which would be impossible. All attempts to reduce their numbers through commercial fishing or other harvesting measures would not significantly alter the negative impacts of this fish, as their rate of reproduction is simply too great.


The Silver Carp not only destroy a lake’s ecosystem, they also impact recreation in a major way. When the fish are startled by a passing boat, they panic and jump out of the water. They can jump as high as six to ten (6– 10) feet. This behavior makes waterskiing, wakeboarding, tubing, jet skiing, and boating extremely dangerous. Even at a slow speed, getting hit by a fish, particularly a large one, can result in serious injury, especially when struck in the face. A 19-year old was tubing when struck in the face by a Silver Carp, resulting in a broken nose and fractured skull/forehead. The only safe boating would be in a large vessel or one with an enclosed cockpit. Unprotected boat occupants would be in great danger. One can only imagine a lake where riding on your jet ski or in your boat poses grave health risk, but this is precisely the case when Silver Carp are present. As the Silver Carp population increases in the lake, the chances of not getting hit would decrease, and the only question becomes “How damaging will a Silver Carp impact be?”


University of Tennessee studies show that the TVA system of lakes produces nearly 12-billion dollars a year from tourism and the many recreational activities found on and around the reservoirs. Tourism will be severely impacted, resulting in a huge revenue loss to the state, counties, cities, marinas, and the many other small businesses associated with lake recreation.

Professional and non-professional fishing tournaments are popular activities on most reservoirs. These activities will suffer greatly and likely disappear due to the Silver Carp impact on game fish populations, as well as the serious danger to the fishermen who typicallymove at a high rate of speed between fishing locations. Silver Carp will place significant stress on all native game fish, as well as forage fish populations, and all will suffer greatly in number and health of individual fish, slowly eliminating fishing tournaments.

As use of the lake for fishing and other recreational activities decreases due to the Silver Carp, people will move away from the water – why pay extra for something you cannot enjoy. The lake property real-estate market will suffer, and property values will drop significantly. This will bring about an economic decline in many aspects of lake-home ownership, including property tax rates and county income from taxes being lost to the county.

There are thousands of small businesses directly and indirectly related to lake recreation. None are immune to economic loss if the Silver Carp reach the area. Hit particularly hard will be marinas, associated restaurants, lake cabin and boat rentals, and even boat sales. These are nearly all family owned and operated businesses whose entire income and livelihood is related to recreation. Unfortunately, many of these businesses will not survive. As well, tackle and bait shops and small fishing camps and sporting goods outlets will face closure.

Clearly, the economic impact from the loss of recreational and tourism industries will be in the hundreds of millions of dollars every year, along with a continual decline in small-business operations. Presently we are seeing an increase in the success of these businesses as well as new businesses being added. These positive economic trends will immediately begin to reverse when the first Silver Carp is seen jumping out  of the water and the sighting is publicized in the media.



There are existing methods which have been implemented to slow or stop migration, and a significant effort is being done by states researching other possibilities. The most proven method is electric barriers. Another promising barrier is the bio-acoustic fish fence.


Electric barriers have been in use since the 1950s. This is a proven technology, and over the years major improvements have been made. Numerous configurations of electric barriers have been used to effectively restrict fish movement. Each system generally consists of a type of electrode (chains, weighted cables, metal bars dangling in the water column, or electrodes placed on the bottom often in groves in a concrete sill and/or up the sides of the channel. A pulsed Direct Current (DC) field is the preferred choice. The electric barrier uses a low-frequency pulsed DC current to create the barrier field. The current is far below the electrocution threshold of a typical home ground-fault-interrupter and is non-lethal.

There are typically six (6) electrodes in a barrier. The first barrier is typically 0.2V dc, with increased voltage in the other electrodes, with the last and highest voltage at 1.2 V dc. The current is dependent on the conductivity of the water, but in even the highest conductivity water, the current is far below any lethal level. There is simply no risk of electrocution to humans who may fall into the water.

Fish are extremely sensitive to any electrical field. When fish initially reach the first electrode, they become quite uncomfortable, even in such a weak 0.2 V dc field, and turn quickly away. A pulsed current affects the muscular control of the fish as well as sensory organs, without permanent injury to the fish. The pulsed DC electrical field can be mathematically modeled depending on depth, water quality, and other factors to produce the necessary field strength. A fish will feel the electric field as it approaches, even though the electric field is quite low. As they get closer, the current and voltage of the field will get stronger and stronger. The fish will turn away quickly, and if it does not and continues toward the stronger current, when it nears the 1.2 Volts, its muscles will constrict and remain constricted rendering the fish unable to swim until it is carried downstream with the water flow and out of the electric field, where it would recover completely. For a complete discussion and technical information about electric barriers see the online PDF:

Though electric barriers do the best job preventing movement of fish, the one problem is that when a large metal/steel barge passes over the electrodes, the field is disturbed. This disruption changes the voltage a fish receives, and it may provide an opportunity for fish under the barge to pass through the field along with the barge. To counter, this, when a barge is approaching the barrier, the field strength can be increased slightly as the barge passes over it. Another countermeasure is the addition of acoustic barriers in front of the electric barrier. Acoustic barriers are not affected by the presence of a boat’s hull. Sonic together with electric, would represent the strongest overall barrier possible.

 Figure 6: Barrier Construction, Electrodes, and Control Room–Photos by Smith & Root


A bio-acoustic fish fence is the combination of a bubble wall, sound, and strobe lights. Research is presently being done regarding sound barriers to deter fish movement. It has been shown that high-frequency sound will deter Silver Carp. However there has not been enough research to conclusively answer what the optimal sound frequencies and pressure levels/volume would be needed to optimize repulsion of the fish. Even with sound, bubbles, and strobes, these barriers are not 100% effective and eventually silver carp could eventually pass through them.

Figure 7 Schematic and Picture of a BAFF


A great deal of research is underway by numerous agencies and states to prevent the spread of Silver Carp. Likewise, some measures have been implemented, and a huge regional effort is underway to further address this problem.

The Kentucky Department of Fish and Wildlife Resources (KDFWR) is working to deter and control Asian Carp. You can view this information on their web site: of additional information is available online and an explanation is provided as to how millions of dollars are being spent to try and gain some bit of control over these invasive carp. As worthy as they are, the information and research in itself will not stop Asian Carp advancement unless the barriers are actuallyconstructed, implemented, and maintained before the carp arrive. Enough monies have been spent on studies. It is time for monies to be spent on the actual construction of electric barriers. Kentucky is also spending significant funds to subsidize commercial fishing of Silver Carp to reduce their numbers. However, no amount of harvest will save the ecosystem or reduce the negative impact on the economic value (recreation and tourism) of the impacted lakes brought about by recreation and tourism. A single large female silver carp can lay 5-million eggs. Kentucky only has a population of 4.49 million people (2019). It is easy to see that harvesting alone is not going to make a significant impact on the Silver Carp population.


In conversations with Smith and Root, the leading U.S company that designs, manufacturers, and constructs electric barriers, the estimated cost to outfit a typical TVA lock with an electric barrier is about $10 million. This is a lot of money; however, one must take into account two University of Tennessee studies funded by TVA that show: (1) the TN River brings in $12 Billion dollars annually, and (2) the local economies average $1-million dollars of economic income per mile of shoreline. Watts Bar Lake has 722 miles of shoreline.

If full funding is not immediately available, a limited liability corporation (LLC) should be formed to obtain loans and/or government loan guarantees, while corporate, government, small-business, and private/individual funding is being raised. Millions of dollars can be obtained if simply every property owner, business owner, and other stakeholders on the lakes would make a tax-free donation of merely $100 or more. Few stakeholders would be unwilling to donate such a small amount to protect such a wondrous resource. There are numerous other ways to help fund this effort, and all costs could be easily funded in time including:

Federal/State/Local government

Lakeside Property Owner Tax

Local Business Donations

Recreational User Tax

Boater use fee/stickerIllinois did this.

Fishing and boating supplies Tax

Fishing Tournaments Fee/Tax

Marina gas tax and slip rental tax


We must bite the financial bullet and strike back at the Silver Carp attack if we have any chance of saving our lakes. We must begin with the immediate installation of electric barriers. A bio-acoustic fish fence should be installed in front of the electric.


Since the Silver Carp are present in Wheeler Lake, there is a good possibility/likelihood they are already at the upstream Guntersville Lock. Fish can and do move quickly within a lake and tend to move upstream. Filter-feeding fish will use a slow current to their advantage by swimming into the flow with their mouths open. This brings a greater volume of water through their gill-rakers with less effort. By design, Silver Carp are continually on the move. TWRA eDNA test results have already indicated that Silver Carp could very likely be in Guntersville Lake at this time.

It is reported that the TWRA is planning to construct a sonic barrier at the downstream side of the Guntersville Lake lock. When operational, the barrier will certainly retard their movement, but being only 80% effective, they will without a doubt breach the barrier and enter Guntersville if they are not already present.

This being said, there is only one conclusion that can be drawn from the facts. We presently have methods that work and are being utilized elsewhere. There is no question that the method of choice is electric barriers. They should be installed as soon as possibleat the Nickajack Lock, and Chickamauga Lock. Once these installations are complete, an installation at the Watts Bar Lock should be done. The process must start immediately as it will take many months to design the specific configuration for a lock, obtain the permits, and initiate construction. Minimum time to complete is 2-3 years.

Due to the time to complete construction, it is imperative that Nickajack be the first, and Chickamauga the second lock outfitted with the barriers, for without a doubt, the fish will have occupied Guntersville Lake by that time. And when complete, Watts Bar Lock construction of a barrier should begin, regardless of whether or not Silver Carp are ever found in Nickajack.  Protection from the migration of the Silver Carp is always a moving target because the fish are always moving. Bottom-line, we cannot delay any longer to begin.

The most immediate need is to bring together TVA, TWRA and the U.S. Corps of Engineers (COE) and work toward completing the necessary approvals. This process alone can be lengthy, but it can also be expedited – it must be expedited. These first action should be to select an experienced manager from each agency. The TWRA is to be tasked with establishing barrier design specifications. The COE would then use these design specifications to produce the actual physical barrier designs with TWRA approval. TVA would facilitate the installation process by regulating water flows. Using experienced staff from each, a formal project team should be established and immediately generate an organization chart, develop a work breakdown structure, divide the workload, establish an expedited schedule, and initiate contact with appropriate companies to begin design efforts.

Initial contracts should be established and funding provided so that design can begin, products manufactured, and schedules for construction set. This process must be multitasked and move quickly, for the carp are indeed moving quickly to ravage and devastate our lakes. We simply cannot afford to take our time or allow agency red-tape to slow this process. All three agencies need to step up to the plate, form this coalition, and move together to make this happen: “It can, if they do.”



Time is of critical importance. Current TWRA field reviews and sample testing show that Silver Carp are present in Wheeler Lake, and eDNA testing indicates they may have already entered Guntersville Lake. If only a few individuals have entered, it may be some time before they are captured, but we cannot forget that a singlemature female fish can spawn several times during the summer laying 4 – 5 million eggs. One need only to do the math to appreciate how rapidly a few fish can lead to a lake overrun with invasive fish in a few short years.
The ecology of our lakes is under attack in a very real way. When University of Tennessee studies show that our lakes are responsible for “Billions” of dollars of revenue to the region, and that every mile of shoreline brings in about a Million-Dollars, how can one possibly put aside protecting that wealth. Fact: that wealth will be lost if we do nothing. Whether it takes 2, 4, or 6 years to destroy our lakes is not the question _ they will be devastated unless we act “Now” to protect what remains of the TVA system presently free of Silver Carp. There is no question whatsoever that the amazing wealth brought about by a healthy lake ecosystem will be gone along with the ecosystem itself. This is not supposition, it is not a mere threat, it is not fear mongering, it is ecological reality in every sense of the word.

One need only look at (1) the ecosystem devastation, recreational, and economic impacts that have already occurred throughout the Mississippi Basin: (2) the forecasts of the billions of dollars of revenue loss predicted to occur if the Silver Carp fully invade the Tennessee River and it tributaries; and (3) hazards associated with boat motoring through a wall of airborne fish to fully appreciate what the future holds if these fish reach our lakes.

Considering that each mile of our shoreline is valued at a million dollars to the local economy makes the cost comparison to implement control measures at the locks insignificant. A dollar value cannot be place on a huge, healthy, aquatic ecosystem. Pay a little now or suffer huge economic and environmental consequences later seems like a very easy choice to make. Money spent today will be orders-of-magnitude less than if we are challenged with the problems of dealing with them if they reach our beautiful lakes. There will be “absolutely no” possibility of recovering from such an invasion – preservation is our only hope.


The Roane County Commission Should: 

  1. Establish an ad-hock “Invasive Species Committee.” This committee would address both invasive aquatic plants and the invasive silver carp.
  2. Request involvement on the Committee from Meigs, Loudon, Rhea, Anderson and Hamilton Counties.
  3. Write a joint 6-county resolution to the Governor of Tennessee asking for the establishment of a joint TVA, TWRA, COE task force to:
    1. Begin the approval process for the use of electric barriers in TVA river system locks.
    2. Obtain funding to begin the engineering design for Nickajack.
    3. Identify all potential funding opportunities.
  4. Sponsor Public Education Workshops for Roane, Meigs, Loudon, Rhea, Anderson and Hamilton Countiesregarding the ecological, fishery, and economic impacts brought about by invasive species.