An Exotic Problem
Exploring the persistent and pervasive nuisance of Asian Carp
Story by Russ Thompson
Whether or not the spread of Asian carp in our Mid-South waters is a nuisance or a threat depends on who you ask. One thing is for certain — it is becoming a problem for anyone who enjoys outdoor recreation in our native rivers and lakes, as well as for anyone who is concerned about the welfare of local aquatic environments. The numbers are growing and, like any exotic species left unchecked by native predators, there will be consequences for the native species of plants and animals.
The story begins with good intentions, like the introduction of most exotic species. They were originally brought over as a food source for fish markets and as a means of controlling algae in aquaculture facilities. However, in the ‘70s, many of them escaped — mainly from Mississippi delta aquaculture ponds — and spread to the North and South. The primary cause of the spread of carp was flooding in the ‘80s and ‘90s. In the Illinois River to the north, it is estimated the carp make up as much as 95 percent of the fish population. From 1991 to 2000, the carp population spiked dramatically in the Illinois and Mississippi Rivers. Just between the years 1994 and 1997, the amount of fish being caught commercially in the Mississippi went up to 55 tons from 5.5 tons.
The two major problem species are silver and bigheaded carp, although there are other species such as the grass and black carp present in lesser numbers. Although some Asian carp can reach sizes of more than one hundred pounds (especially those of the bigheaded variety), most average around 30-40 pounds.
The primary issue with these deep-bodied fish is consuming mass quantities of food that our native species depend upon as a food source. Asian carp tend to eat algae and plankton, food sources that native fish in the Mississippi, Tennessee and Cumberland Rivers require. They are voracious eaters, often consuming 5 to 20 percent of their body weight in a single day. Adult paddlefish, shad and buffalo depend upon this same food source, as do bass, bluegill and crappie in their early stages of life.
In addition to the competition with native species, the silver carp actually pose a threat to humans directly. “Boats make a noise at a certain frequency that makes the silver carp want to jump out of the water for some reason. This can be dangerous if they jump onto people’s boats and injure them,” says Chad Washington of the Mississippi Department of Wildlife, Fisheries and Parks. The fish can jump as high as 10 feet out of the water, and have been known to injure people and damage property.
According to Washington, it’s a borderline situation in Mississippi. “The numbers are growing. We see it when we ride out into the rivers and some lakes, especially the ones connected to the Mississippi River. We are seeing bighead carp and silver carp, although silver carp are much higher in number.” The carp have reached as far as Old Hickory Lake near the Cumberland River System and as far east as Wheeler Lake of the Tennessee River system in Tennessee. “Due to the fact that these fish are plankton feeders competing with our native fish and the danger silver carp pose to recreational boating from these large fish jumping out of the water, I would have to say this problem is indeed a threat,” says Michael Butler, CEO of the Tennessee Wildlife Federation.
Many solutions have been proposed to handle this situation, some more successfully than others. Some are in favor of manipulating the genes so that only male carp are produced. Others have proposed toxins or diseases that will only affect carp populations. Unfortunately, little progress has been made on these fronts. As far as detection goes, a method called eDNA (environmental DNA) is being used to determine the presence of carp genetic material in certain waters. One problem with the use of eDNA is that is doesn’t tell you if it came from a living or dead animal. Once scientists find the presence of this DNA they can combine this method with others, such as netting to get a better idea about the population.
To the north, the problem is a serious enough threat to have garnered a coordinated response to the situation. The US Army Corps of Engineers set up an electric barrier to prevent the carp from entering the Great Lakes basin from the Illinois and Mississippi Rivers. According to US Fish and Wildlife Service Deputy Midwest Regional Director, Charlie Wooley, the leading edge of the carp population in the Illinois River is still 40 miles to the south of the Great Lakes. “I am hopeful that the barrier will keep them out.”
Wooley says that the population of carp number in the millions in the upper/middle Mississippi, Illinois, lower Missouri, and lower Ohio Rivers. However, the populations are showing a downward trend due mostly to the efforts of the state of Illinois, who is sponsoring and contracting local fishermen to catch large numbers of carp for fisheries.
The problem of keeping Asian Carp out of the Great Lakes brought together officials on the local, state and national levels to address the issue. The Asian Carp problem had gotten to be such a great problem in the Ohio and Upper Mississippi basin that it inspired the Water Resource Reform and Development Act in 2014, which created an expanded response. It includes a partnership between the US Fish and Wildlife Service, the US Army Corps of Engineers, the National Park Service and the US Geological Survey. What resulted was a report given to congress about continued coordination between all of these partners to prevent and control levels of carp in these river basins. Now congress continues to allocate money for the continued efforts to decrease the population.
Washington says that they are in the beginning stages of studying the effects of these fish in Mississippi lakes and rivers. “We sample them using netting techniques and compare the results to what was found in studies done 20 years ago. We try to estimate age, structure, numbers and how fast they grow. Currently, we are randomly sampling in locations where many carp have been spotted.”
Washington feels that the best solution is help from commercial fishermen. “Many people are scared to eat the carp, although the meat is quite mild and tasty. Right now, we can’t get anyone to offer enough per pound. In Mississippi, markets are only offering a dime per pound, which is much lower than what they get for most native species. The main market for this fish is actually in China.” Moon River Foods is a company that has begun operations in Baird, Mississippi. The company buys carp and other fish from local fishermen, processes the fish and ships it to China for consumption. Plant manager Jimmy Taylor says that he estimates that the fishermen bring in as much as 1.5 million pounds of fish per year that come mostly from lakes. The fishermen tell him that the carp they catch are especially abundant in Tunica, Eagle, and Choctaw lakes.
“Last spring, a study committee formed the Asian Carp Task Force to address the threat of Asian Carp in Tennessee, with leadership and funding from state legislators such as Senator Mark Green and Representatives Tim Wirgau and Jay Reedy. It is largely in the fact-finding phase at this point,” says Butler. The task force reports its findings back to Congress, which helps fund the recommended actions. Currently, there is a lot of focus on raising awareness and efforts to monitor the populations. Experts are meeting and discussing ways of limiting and controlling their numbers, and making the public aware of the problem through the distribution of wallet cards, posters and signs. In an effort to discourage further spread of the species, the TWRA has also made it illegal to transport live carp. Local fisherman and celebrity Bill Dance has started a campaign in coordination with the TWRA to educate people about the negative effects that come with introducing the fish to other waters. Also, it has been proposed that chemicals be put in the water, which would harm only the carp, but this development could take 10 years or more.
The TWRA is concentrating most of its management activities on the Tennessee and Cumberland Rivers due to the vastness of the Mississippi. The leading edge of the population (population of spawning adults) stretches from Gunthersville Reservoir on the Tennessee River all the way to the Old Hickory Lake in the Cumberland System. One of the proposed solutions is to put CO2 bubble screens and noise generators on dam locks to deter the carp. They are also trying to promote carp harvest by local fishermen. In addition, they are monitoring known populations in the Cheatham, Barkley and Kentucky Lakes by relying on the knowledge and help of commercial/sport fishermen to remove the fish. Some of the silver carp, which tend to move in large groups, are being tagged so that their movements can be tracked.
For all of those individuals concerned for the well being of our native waters, this will be an ongoing issue. For now, it appears our native fish still stand a chance against the hungry carp in the Mid-South if we learn the correct lessons. In order to keep the situation from reaching a crisis level, we need to continue to monitor and limit their numbers, change the perception people have of carp meat, work to raise the price that fishermen receive for the meat and educate people about the dangers of transporting them from one area to another. If these efforts are successful, hopefully we can keep the nuisance from becoming a more serious threat.