Asian Carp are about as much of a household name as a toothless invasive fish can become thanks to their high flying nature and rapid spread throughout North America. While much has been said on this species, the problem has by no means been solved and continues to threaten our Great Lakes as they climb their way north.

What They Are and How They Got Here

While Common Carp were also technically introduced, these less intrusive fish are considered native to many of our lakes and pose no threat to local ecosystems other than being considered a nuisance fish to most fishermen.

Asian Carp however, are an extremely invasive species and have been posing major threats to their new ecosystems ever since their introduction in the 1970’s. These Asian species of Carp include the Bighead Carp, Black Carp, Silver Carp, and Grass Carp. These invasive fish were first introduced to the United States to help control weeds and parasites in aquatic farms. The carp quickly spread into the Mississippi River and established breeding populations. Since their spread into the Mississippi, these fish have spread north and are now being spotted in the Great Lakes, establishing breeding populations in Lake Erie and Ontario due to flooding, human activity, and their ability to jump over man made structures.

The Problem With Asian Carp

Competition with Native Species:

The main issue with Asian Carp is their mass consumption of resources. These invasive species of carp can consume up to 20% of their bodyweight in resources each day (OISAP, 2015). This includes plankton and small fish for the Black, Silver and Bighead Carp, and aquatic vegetation for the Grass Carp. This consumption poses major problems to native species who rely on this food source as Asian Carp can weigh up to 100lbs (Rafferty, 2010).

This overconsumption of local food sources has proved to cause a decrease in the population of native species of fish. Proof of this can be seen in the Illinois River where Asian Carp were once making up 90% of the river biomass (Stop Carp Coalition, 2011). The Illinois River is located 120 miles north of the Mississippi River and has the largest density of Asian Carp in the world. This case proves the ability of these carp to takeover bodies of water, forcing native species out, and drying up ecosystems of their species and resources.

Altering of Shorelines:

Asian Carp are not only damaging ecosystems by outcompeting local species for resources, but are also significantly altering the structure of the bodies of water that they are invading. The main culprit for this is the Grass Carp. The Grass Carp is a species of Asian Carp that feeds entirely on aquatic vegetation. Due to the rapid reproduction rates of these fish and limited competition, Grass Carp are able to consume mass amounts of this food source. The effects of this can be seen in the eroding shorelines of the Mississippi and Illinois Rivers due to the distinct lack of vegetation growing in places where it used to flourish (NPS, 2016).

Destruction of Habitat

This overconsumption of resources is not only affecting the native species of fish, but also terrestrial creatures that rely on these bodies of water. This includes the birds and mammals that prey on the fish and the insects and rodents that live in the water and along the shorelines. Over 100, 000 loons, gulls, mergansers, and other migratory birds have washed up on the beaches of Lake Michigan in the last 20 years, more birds than were killed during the oil spill in the Gulf of Mexico in 2009 (Chicago Tribune, 2010). These trends have continued in the Great Lakes as the same phenomena has been seen on the shores of Lake Erie and Lake Ontario since the first sightings of Asian Carp in these waters.

Lack of Predators:

In Asia, the natural carp populations are kept in check by natural predation from fish species, as well as by humans as the carp are caught for sport and for consumption in large quantities. In North America, however, carp have no true predators. This allows the carp to rapidly reproduce and outcompete for resources, preying on other species while being avoided by native predators due to their size and unfamiliarity. The human aspect is largely taken out of the equation as well, as the fish are not considered game fish and are not regularly targeted or consumed like they are in other parts of the world.

Economic Losses:

The sport fishing industry alone supplies over 50,000 jobs and contributed roughly $3.80 billion to the Great Lakes region’s GPA in 2015 (TVO, 2015). In total, Ontario’s commercial fishing industry is valued at over $13.8 billion when socio-economic factors are considered (TVO, 2015). This once again raises the issue of these fish’s ability to over consume resources and run out native species of fish. This is an especially high concern in the Great Lakes as the integrity of the plankton population has been in question in recent years. Plankton being the bighead and silver carps main food source heightens the threat significantly as a collapse of the plankton population could bring the entire fisheries business in the region down with it (TVO, 2015).

Asian Carp are also known to jump over 10 feet out of the water, posing problems to keeping fish behind structures and potentially harming boaters and other recreation seekers on the infested waters. These species tend to damage public perception of the water because of this issue as there have been reports of broken noses and bruised ribs as a result of these 20 plus pound fish leaping out of the water at high speeds (TVO, 2015). Asian Carp tend to jump out of the water around people rather frequently as a result of being startled by boat motors or any loud noises in the water. This makes users of the Great Lakes even more susceptible to these leaping carp as there is generally very high boat traffic in these areas.

What is Being Done?

Because of the immediate risk of these fish to the ecosystems and the people that surround them, methods are currently being examined to control these species that can be implemented immediately. Pound nets, hoop nets, and flyke nets are all being deployed by local governments in order to stop the spread. The difficulty of this is taking into account the carp jumping ability and how this will limit the success of the methods created. Pound nets are large, stationary nets that are very common in marine environments, as well as in the Great Lakes as they are deployed for long periods of time and require a lot of space (Collins et al, 2015). The amount of space required for the deployment of a pound net makes their use in smaller bodies of water unknown and rarely used. This is where hoop and flyke nets are utilized, as they are able to be deployed in smaller bodies of water and require less people to deploy and retrieve. This will be necessary, as the Carp are not only invading the main water of the Great Lakes, but also the channels and smaller lakes surrounding them.

In terms of addressing the populations that already exist in the lakes, other states have begun exploring some creative options. One example of this is the re-introduction of Alligator Gar to the carp infested waters of Indiana, Illinois, and Kentucky. These large predatory fish were common in these areas for decades until the early 1970’s where the numbers plummeted significantly. These species of Gar can grow up to 8 feet long and are deemed as “natures control critters” by the Evansville Courier & Press. They were given this nickname, as the Alligator Gar does not prey on game fish but rather on shad and common carp. Due to the Gars once established populations in these waters, there does not appear to be any negative implications from the re-introduction of these species. This project wont be completed however until 2026, as it takes approximately 17 years for the Alligator Gar to reach sexual maturity (Courier&Press, 2011).

Invasive Species Spotlight: Asian Carp