Silver Carp: Public enemy number one

The infestation of Asian Carp into America’s rivers and lakes may be the biggest threat to our water ecology, boating, and fishing we have ever faced.

Asian Carp are a non-native, invasive species of fish in North America. Types of Asian Carp in the Tennessee River watershed include Grass, Black, Bighead, and Silver carp. Silver carp are of most concern. The Ohio River, Mississippi River, Cumberland River, and the Tennessee River are threatened by this invasion.

This invasion of carp threatens the management of fisheries, sport fisheries, ecosystems, recreation, and economic development. You have most likely seen videos or photos of the silver carp getting excited and jumping out of the water in huge numbers. This unusual response to boat motors makes this variety of the Asian Carp very dangerous to skiers, jetski riders, and boaters, especially in watercraft moving at high speeds.

State wildlife and conservation agencies, the Tennessee Valley Authority, the U.S. Geological Survey, U.S. Fish and Wildlife Service, and the U.S. Army Corps of Engineers are the major players in addressing the problem of infestation of the Asian Carp in our lakes and streams.

The Asian Carp has four different species: grass carp, big head, black carp, and the most troubling, the silver carp. The grass carp is found across the country while the black carp have made the mid-west south it’s home. The bighead carp can be found in waters of the central U.S. The problem variety, the silver carp, has also managed to make many waterways and lakes concentrated in the central U.S.

Stopping the migration of the silver carp into connected rivers and impoundments is the primary concern of agencies involved.

The USGS Asian Carp (U.S. Geological Survey) research identifies the Asian Carp as a threat to expand into new waters, imperiling the multi-billion fisheries of the Great Lakes, Upper Mississippi River, and the Tennessee River. Silver carp have been discovered in Alabama as far upstream as Wheeler Lake. However, none have been sited in Guntersville or Wilson Lakes of North Alabama. All of the carp species except black carp are present downstream in Pickwick Lake. No tagged carp have moved thru Wilson or Wheeler locks.

One question to be answered is how silver carp arrived in Wheeler Lake with none sited in the impoundments located downstream or upstream. One possibility is that the fish may have been introduced by fishermen using live bait collected from an impoundment like Pickwick where there is a known silver carp population.

Two silver carp was caught by gill nets in Bay Springs Lake, Mississippi by Mississippi State University researchers. The researchers have implanted transmitters in 35 silver carp since November 2017 and saw that carp were moving into Kentucky and Barkley Lakes.

The Asian Carp
Young Asian Carp closely resemble other baitfish like the skipjack herring, gizzard shad, and threadfin shad, The most identifying feature of the silver carp is the position of the eyes. The eyes of the fish are located far lower than the similar baitfish.

Silver carp are believed to migrate upstream and pass through locks. But, the data is uncertain regarding their abundance, movement, and reproduction rates. Silver carp are very prolific and can quickly become over-abundant, which can lead to adverse impacts on native fish populations in the lakes and rivers that they infest because they out-compete other fish for food and space.

Silver carp with eggs have been discovered in the months of March thru September/October. Mid-June thru July appears to be the peak of the carp’s spawning. Some of the carp are one-time spawners while others spawn multiple times.

Migration Interdiction
The USGS has identified tailrace harvesting, driving, and trapping as among the suggested methods of Asian Carp control methods.

The Tennessee Water Resource Agency (TRWA) has said that 3.4 million pounds have been removed commercially since July 2019. The TRWA has also initiated a program to prevent accidental spread using outreach, education, and bait regulations. Some state agencies have enacted statewide bans on transporting live, wild-caught bait between public lakes and reservoirs. The establishment of an Asian carp market for commercial fishing would be a major source of removing the carp from impoundments.

Chris Green, with the Alabama Game and Fish Division, said in a September 4, 2020 news release, (See WFF Cautiously Optimistic About Spread of Silver Carp) “Because of the abundance of silver carp in their rivers and reservoirs, Kentucky and Tennessee rely heavily on commercial anglers to remove silver carp from their systems. Greene said those states even subsidize commercial anglers to remove silver carp to make it economically feasible.” However, once the invasive fish is established in a body of water they will not be completely removed.

Among the intervention methods being tested and developed at locks and dams are the Bio-Acoustic Fish Fence (sound, bubbles, and light), net barriers, mass removal methods, contracting with fishermen to remove the carp, electroshocking, acoustic deterrent system, carbon dioxide system, electric barrier or a combination. The deterrent systems are to be deployed at pinch-points at dam locks. Asian carp are vulnerable to underwater sound and avoid underwater pressure waves.

The USGS Asian Carp monitoring will be accomplished with seasonal gill net sampling, electrified dozer trawling in summer, and collection of biological samples to determine population density. Early detection will be made using eDNA and electrofishing. The USGS is surgically implanting acoustic telemetry tags in carp to identify movement patterns through locks and dams. All locks and dams on the Tennessee River to Guntersville Dam and three locks and dams on the Cumberland River will be equipped with acoustic receivers to track the carp.

The Tennessee Valley Authority (TVA) is managing a Programmatic Environmental Assessment (PEA) for fish barriers at 10 TVA Locks is underway. The study is evaluating potential fish barrier options at each TVA lock. Results from Asian Carp research will be used to determine which type of barrier or combination is recommended per lock.

The TVA agency will also be conducting “FluEgg” modeling. This research is to determine where Asian Carp eggs can hatch. The results of this research will provide resource managers information to target areas where spawning is likely and areas where Asian Carp fry may be found. This information will also tell TVA River Management of options to help reduce the likelihood of successful fry hatching by manipulating water flows.

Annual valley-wide fish and benthic macroinvertebrate assessments will be conducted by TVA to determine the effects of Silver Carp on aquatic communities.

Green also said in the news release, “We’ve been sampling with our standard shock boats,” he said. “The new boat will be more

specialized with a rectangular frame and net attached to the front of the boat where you can actually trawl through the water. It will still have electrodes hanging down like a standard electrofishing boat. So, you’re moving through the water collecting carp in areas where they tend to congregate.

There is a sense of urgency to establish barriers on the Tennessee River but funding is needed. Barriers will be put in place as soon as possible when funding is received. The type of barriers deployed vary with sites.

The Asian Silver Carp is a clear and present danger to our rivers and impoundments.

(Resources used include statements and slides presented during the Silver Carp Roundtable (digital) August 5, 2020, moderated by Thom Benson, Tennessee Aquarium.)