How USGS Science Helps Managers Fight Invasive Asian Carp

"Asian carp" here means four fish species brought to the United States in the 1960s and 1970s that now breed in U.S. waters. Their life histories are alike, but their diets and ranges differ:

• Bighead and silver carp filter plankton from the water and are established across much of the Mississippi River Basin.
• Grass carp eat submerged water plants; they are widespread in the United States, with a growing number of breeding populations, including in the Lake Erie watershed.
• Black carp eat freshwater mussels, snails and other mollusks; their range in the Mississippi River is limited but expanding.

A bighead carp. USGS.

The U.S. Geological Survey's Asian carp research aims to keep them from becoming established in the Great Lakes and to reduce their harm in the Ohio and Mississippi River Basins and elsewhere, through early detection, risk assessment, and tools and strategies for control. Its tools are designed to extend to other invasive species and other regions. The work supports the Great Lakes Restoration Initiative, a multi-agency effort begun in 2010, and the USGS sits on the Asian Carp Regional Coordinating Committee with federal and state agencies, Canada and others. Thirty years of research on the fishes' biology underpins control strategies built on integrated pest management — solving pest problems while keeping risks to people and the environment low.

Finding them early

Asian carp dodge nets and other gear, so they are hard to catch, especially when there are few of them. Genetic methods can detect them at low numbers and catch new invasions.

• Environmental DNA (eDNA) — DNA found in a sample of lake or river water. USGS refinements have made detection more sensitive, cheaper and faster. Research now asks whether eDNA can show fish movement, habitat use and spawning, measure whether management works, estimate how many carp are present by weight, and how eDNA changes over time after leaving a fish.
• A portable kit. With industry, the U.S. Fish and Wildlife Service and state agencies, the USGS tested and validated a commercial eDNA kit that gives results in under an hour instead of days. In trials, law-enforcement officers with no prior experience used it to detect a single minnow-sized silver carp mixed with more than 10,000 fathead minnows in a large tank. Protocols are being written, and officers are to be trained and equipped through the Great Lakes Restoration Initiative.

Judging the risk

Risk assessments estimate how likely a species is to invade, spread or do economic or ecological damage, and which places are most at risk, so managers can aim their monitoring and control. The USGS completed an international risk assessment of bighead and silver carp with the Government of Canada, is part of a partnership assessing grass and black carp, and builds easy-to-use decision tools from the results.

• Where they could spawn. Not every river suits spawning. The USGS model FluEgg (Fluvial Egg Drift Simulator) predicts where conditions would let bighead, silver and grass carp eggs and larvae survive until they reach nursery habitat. It can assess the risk of new spawning populations — where carp live now and where they don't yet — test control measures, and show managers where spawning might be disrupted.
• Food in Lake Erie. Satellite images show there is enough food in Lake Erie for bighead and silver carp: the green and blue-green algae at the surface that they prefer. Water temperatures and algae levels from 2002 to 2011 show both species could live and grow there — and, if they did, harm native fish and the region's economy. Aquatic plants in Lake Erie are being mapped to judge the food available for grass carp.

How FluEgg follows eggs from spawning, through drift, growth and hatching, to the larval stage when the gas bladder inflates. USGS, from Murphy and others (2016).

Keeping them out and knocking them down

USGS scientists are developing and testing containment and control tools, alone and in combination — hot water and ozone among them, as well as:

• Flow data at the gateway to the Great Lakes. With the U.S. Army Corps of Engineers, the USGS measures flow and water quality at Brandon Road Lock and Dam and elsewhere on the Illinois River and Chicago Area Waterway System, so controls work even when storms and lock operations change the flow. With the Fish and Wildlife Service it has studied whether young carp could move into uninvaded waters, even past the electric dispersal barriers, and measured how water moves around barges.
• Carbon dioxide. Silver and bighead carp avoid water high in CO₂. The USGS is testing how carp behave in CO₂ gradients in the field and how to deliver the gas, for example above locks and dams. CO₂ works as a deterrent and could be combined with electric and sound barriers for backup.
• Microparticles. A layered particle sized for the mouths of bighead and silver carp but smaller than most native fish eat carries a toxicant — initially Antimycin A, an EPA-registered fish poison. In the lab, carp that ate the particles died while bluegill and largemouth bass did not; in experimental ponds with algae attractants, the particles killed many silver and bighead carp but no largemouth bass. Field trials are being planned, and the particles are being adapted for other toxicants, for grass carp and for other invasive species.
• Algae lures. Asian carp are strongly drawn to certain mixtures of algae. "Feeding stations" releasing these attractants are being used with nets and traps to pull carp in for capture, tested together with sound, and tried as a way to draw fish to microparticles.
• Underwater sound. With the University of Minnesota, the USGS found that bighead and silver carp react strongly to the broadband sound of an outboard motor, swimming away as many as 37 times in a row, while native fish barely responded — so sound might keep carp out of an area while letting native fish pass. Sound is also being tested to herd fish for capture.

USGS scientists measuring flow velocity in a lock channel. USGS.

Brandon Road Lock and Dam

In its Great Lakes and Mississippi River Interbasin Study, the Corps of Engineers is weighing a single control point at Brandon Road Lock and Dam in Joliet, Illinois, to stop Asian carp and other aquatic nuisance species moving upstream from the Mississippi River Basin into the Great Lakes Basin. The site's position makes it the one place every species heading upstream toward the Great Lakes must pass. The USGS supplies the flow and water-quality data and analyses behind barrier decisions and tests of control tools.

Brandon Road Lock and Dam, the downstream control point of the Chicago Area Waterway System. U.S. Army Corps of Engineers photograph, April 22, 2014.

Putting tools to use

The USGS works with managers to learn what they need, and runs training and workshops on new tools and findings. Chemical and biological controls must meet environmental regulations, so the USGS is working with the Fish and Wildlife Service and the EPA on the data needed to register CO₂ and Antimycin A microparticles with the EPA and state regulators, and to choose species for testing effects on threatened and endangered species.

The damage Asian carp already do in North America is far-reaching and could grow. Many organizations are working to keep them out of the Great Lakes and other waters and to control them where they live; the USGS's objective evaluation of control tools is a particularly important part of that effort.

Sources

• Cynthia S. Kolar and Sandra S. Morrison, USGS Science and Technology Help Managers Battle Invading Asian Carp, USGS Fact Sheet 2016–3063, September 2016. https://doi.org/10.3133/fs20163063
• The banner illustrations of the four carp (© Joseph R. Tomelleri, used with permission) are not reproduced here.