Move Aside Suckermouth Catfish, 25,000 Tonnes of Giant Carp Now Being Eradicated

Suckermouth catfish once caused widespread alarm due to their massive presence in Jakarta’s waters. These invasive fish, which breed extremely rapidly, are considered destructive to river ecosystems and require eradication. Similarly, the United States is facing a comparable crisis, though instead of suckermouth catfish, it is giant carp—some as large as big dogs—that are ‘invading’ their waters.

These invasive carp have caused ecological damage for over a century, but local officials have reached a significant milestone in the fight against these giants. Over the last 15 years, wildlife officers have removed 50 million pounds (approximately 25,000 tonnes) of invasive carp from the Illinois River in the US. This weight is equivalent to roughly 5,000 elephants, according to reports.

This removal is part of a broader, coordinated effort to protect rivers and lakes from non-native species. The situation mirrors that of the suckermouth catfish in Indonesia, which is not a native species but originated from Brazil. Currently, four invasive carp species pose a threat to the Great Lakes and surrounding areas: bighead carp, silver carp, black carp, and grass carp.

The Great Lakes, the largest group of freshwater lakes on Earth, contribute 20% of the world’s surface freshwater. According to the Great Lakes Fishery Commission, these four species were imported to North America in the 1970s to assist with pest control in aquaculture facilities. However, they escaped captivity within just 10 years and spread through the Mississippi River basin and other major rivers, including the Missouri and Illinois.

Each of the four species can weigh over 45 kilograms and grow up to 1.2 metres in length. Bighead and silver carp primarily consume small plankton, while grass carp feed on aquatic plant roots. Black carp mainly consume molluscs and snails. Peter Alsip, an ecologist at the NOAA Great Lakes Environmental Research Lab, noted that these fish consume such vast quantities of food and exist in such high numbers that they can significantly deplete resources for native species. By consuming phytoplankton and zooplankton, they disrupt the very foundation of the food web.

In areas where invasive carp are abundant, they have damaged other fish species and disrupted both commercial and recreational fishing, according to the United States Fish & Wildlife Service (USFWS). They also pose a physical danger to humans, as these giant fish can leap out of the water and strike unwary boaters.

Efforts to eradicate the carp have been ongoing for over 100 years, involving targeted mass removals, the development of barriers to block movement, and continuous monitoring. The removal of 50 million pounds of fish from the Illinois River focuses on the northern section of the river, about 50 miles from Lake Michigan. The project is designed to suppress the adult population, limiting their ability to reproduce and reducing migration towards the Electric Dispersal Barrier System.

Located about 37 miles from Lake Michigan, this electric barrier is designed to prevent movement through the Chicago area and is a primary tool used by wildlife officers to stop the carp from entering the Great Lakes via the Illinois River. Other programmes along the Illinois River offer harvest incentives to commercial fishermen along a 240-mile stretch downstream. The USFWS stated that by removing more invasive carp, they can reduce the negative impacts and the risk of them reaching Lake Michigan, thereby protecting valuable native fisheries and the regional Great Lakes economy.