Do snitches net fishes? Scientists turn invasive carp into traitors to slow their Great Lakes push

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Wildlife authorities across the Great Lakes region are employing a rather unconventional strategy to combat the spread of invasive carp. Over the past five years, governmental agencies such as the U.S. Fish and Wildlife Service and the Minnesota Department of Natural Resources have initiated a seek-and-destroy mission that involves using “turncoat” carp to reveal the locations of these troublesome fish.

This intriguing approach involves converting carp into double agents by capturing them, implanting transmitters, and then releasing them back into the waters. Floating receivers equipped with these transmitters provide real-time notifications whenever a tagged carp swims nearby. Carp tend to aggregate in groups during the spring and fall seasons. Armed with the information gleaned from these “traitor” carp, agency personnel and commercial anglers can pinpoint these locations, deploy their nets, and extract multiple invasive fish from the ecosystem.

Kayla Stampfle, the invasive carp field lead for the Minnesota Department of Natural Resources, elucidated the strategy: “We utilize these fish as a means to an end, strategically setting nets around the tagged fish.”

Four distinct species of invasive carp—namely, bighead, black, grass, and silver—pose a significant threat. Initially imported to the United States in the 1960s and 1970s to control algae, weeds, and parasites in southern aquaculture farms, these carp escaped into the wild due to flooding and accidental releases. They subsequently infiltrated the Mississippi River and have since utilized it as a conduit to proliferate northward into rivers and streams in the country’s midsection.

Invasive carp are voracious eaters, with adult bigheads and silvers capable of consuming up to 40% of their body weight in a single day. This insatiable appetite enables them to outcompete native species, disrupting aquatic ecosystems. Although precise estimates of invasive carp populations in the United States are lacking, it is believed that they number in the millions.

Collectively, state and federal agencies have invested a staggering $607 million in efforts to curb the spread of these fish, with projections indicating that expenditures may reach $1.5 billion over the coming decade.

Eradicating invasive carp in the U.S. is deemed nearly impossible. Consequently, the primary objective is to prevent their entry into the Great Lakes and safeguard the region’s $7 billion fishing industry. Various measures have been employed, including electric barriers, bubble walls, and herding carp into nets using underwater speakers. However, the fish have managed to breach defenses, advancing as far as northern Wisconsin along the Mississippi, while grass carp have been found in Lake Erie, Lake Michigan, and Lake Ontario.

To combat this incursion, agencies like the U.S. Fish and Wildlife Service and state wildlife managers have established a network of receivers spanning from the St. Croix River in northern Wisconsin to the Gulf of Mexico to track the movement of tagged invasive carp. The initial receivers were deployed in the Illinois River to impede migration into Lake Michigan in the early 2000s.

Starting around 2018, modern, solar-powered receivers were strategically placed throughout the Great Lakes region. These receivers can track tagged carp and send immediate notifications to observers, revealing potential carp gatherings prior to migration and shedding light on movement patterns. This data enables agencies to plan expeditions to remove carp from the environment and tag additional “traitor” fish.

These receivers consist of a raft equipped with three solar panels, housing a locked box containing a modem and a computer for recording contacts with tagged carp. Remarkably, the receivers can detect signals from tagged fish over a mile away.

Each receiver comes with an estimated price tag of $10,000. The federal Water Resources Reform and Development Act of 2014 authorized a multi-agency campaign against invasive carp in the upper Mississippi River and Ohio River basins, permitting the U.S. Fish and Wildlife Service to allocate funds for these devices.

These receivers have been deployed in various critical locations, including Lake Erie, the stretch of the Mississippi between the Illinois and Missouri borders, the Illinois River, and riverways in the Chicago area.

The U.S. Fish and Wildlife Service has established four real-time receivers in the Mississippi backwaters, ranging from Davenport, Iowa, to the Missouri border. The U.S. Geological Survey has also deployed over a dozen devices, including receivers in the Chicago Sanitary and Ship Canal, the Des Plaines and Illinois rivers in Illinois, and the Sandusky River in Ohio.

While wildlife agencies are in the process of consolidating data on the impact of real-time tracking, they assert that the “traitor fish” strategy has been effective. In particular, in the Mississippi region spanning from the Illinois-Iowa Quad Cities to the Iowa-Missouri border, real-time tracking has enabled wildlife managers and anglers to double the removal of invasive carp annually.

Critics within the fisheries industry have expressed concerns over returning tagged invasive carp to the wild, where they can continue breeding. However, proponents argue that in the battle against invasive carp, all available strategies must be employed.

“In theory, it works,” said Marc Smith, policy director at the National Wildlife Federation’s Great Lakes Regional Center. “We believe the benefits outweigh the risks. We have to employ every available tactic. We cannot afford to rule anything out.”

Despite the challenges, wildlife agencies remain committed to the ongoing battle against invasive carp. Understanding the movement patterns of these fish is seen as a crucial element in the quest to mitigate their impact. As Kayla Stampfle aptly puts it, “When are these fish moving? If we can figure that out, it gives us a fighting chance. Can we keep up with them? I don’t think anyone can answer that accurately. It’s still unknown territory. It’s an uphill battle on a very slick slope. You just pray you have a foothold.”

Frequently Asked Questions (FAQs) about Invasive Carp Management

More about Invasive Carp Management

• Great Lakes Fishery Commission – Invasive Carp
• U.S. Fish and Wildlife Service – Asian Carp
• Minnesota Department of Natural Resources – Invasive Carp
• The Big Big News – Invasive Carp Control Costs