Since the invasive carp problem is a binational and multistate problem, the U.S. federal and state governments are working with Canada to find a solution. Since the 1980s, small amounts of grass carp have been caught in the Great Lakes and their tributaries. «For our reproductive tests, we perform ploidy analyses by examining blood samples from herbivorous carp using optical microscopy,» Mahon said. «Finally, we use genomic methods to study the population structure of grass carp in areas where we can collect and take samples.» Michigan State University Extension and Michigan Sea Grant answer a variety of questions each year from Michigan pond and lake owners who are struggling to control excessive growth of aquatic plants. Often they ask if they can use grass carp to solve their problem of excessive growth of aquatic plants. The answer is «no» because it is an illegal species that belongs to the State of Michigan, except under a permit from the Michigan Department of Natural Resources for educational or research purposes. This is often confusing for Michigan residents, as the neighboring states of Illinois, Indiana, and Ohio allow the use of grass carp under certain conditions with the appropriate permit. Brenden studies the movement of grass carp in western Lake Erie using acoustic telemetry transmitters. According to Brenden, these transmitters are electronic tags that are surgically inserted into the abdominal cavity of the fish.
Grass carp was first imported into the United States from Taiwan and Malaysia in 1963 for use as a control of non-toxic weeds in freshwater ponds. The fish escaped and spread across the Midwest through the Mississippi River Basin. While bighead and silver carp are thought to have escaped from aquaculture ponds, grass carp have been intentionally stored in the waters of many states in an effort to control aquatic plants. «At the end of the summer of last year, we did a reaction exercise and the exercise was, `What would we do if we found bighead or silver carp, which is really a serious problem for us, in the tributaries of Lake Erie?` Newcomb says. The U.S. Fish and Wildlife Service commissioned a report on the commercial grass carp industry. Grass carp is one of four species of Asian carp that are of concern to authorities. The majority of Lake Erie`s fertile grass carp are caught off Monroe. Eleven were caught in the Lake Michigan basin last year, all in the Illinois River. Common carp average 15 to 32 inches and 4 to 31 pounds. They have triangular heads, blunt muzzles and small barbels (fleshy filaments resembling whiskers) at the corners of the mouth.
Grass carp feed on plants and are able to consume 90 pounds of food per day. They are only able to digest half of it and hunt the rest. This contributes to dangerous algal blooms and eutrophic conditions that can kill native plants and animals. Therefore, much attention is being paid to the work of researchers and biologists in the Great Lakes states and Canada to prevent invasive bighead and silver carp from moving through the Chicago-area waterway system to Lake Michigan. Grass carp are on Michigan`s watch list for invasive species and are banned. They have large hatched scales, can reach lengths of more than 5 feet, and weigh more than 80 pounds. Their eyes are at the same height as their mouth and have shorter dorsal fins than goldfish or carp. «Educating and educating others about these species can go a long way in combating the spread of these invasive non-native carp species – fish that have the potential to significantly damage or destroy Great Lakes ecosystems and inflict immeasurable losses on Michigan`s economy and world-class natural resources,» Foreman said. Grass carp are herbivorous and feed mainly on coastal vegetation.
They do not exhibit explosive reproductive capacity like the Asian bighead carp and the Asian silver carp that advance in Illinois. These carps, which eat plankton, are considered a serious threat to the Multi-Billion Dollar Sport Fishing Industry of the Great Lakes. More and more sport fishermen like to fight against these fish and some charter operators now offer carp excursions. During this exercise, they caught and analyzed grass carp. They also attached radio stations to grass carp to learn more about their behavior. While Brenden focuses on telemetry to track movements, Mahon works hard to study the genetic, genomic, and fertility status of grass carp. As they are widespread and their demand as a food source has decreased, ordinary carp are sometimes considered an annoying species. However, they are not considered invasive in Michigan. «We find that the vast majority of grass carp are diploid, which is not a good thing,» Mahon said. «However, it is good that we are able to make this data available to management groups to respond to the invasion of these harmful fish.» In addition to this ongoing work in Lake Michigan and its tributaries, staff and researchers at the Michigan Department of Natural Resources` Fisheries Division are also focusing on the problem of grass carp in the Lake Erie basin. Tammy Newcomb says state officials are concerned that grass carp are multiplying in Lake Erie. She says they`re even more worried about two other species of Asian carp: silver (these are the ones that jump out of the water) and bighead carp.
Since the mid-1980s, the herbivorous carp used in this way have had to be sterilized in order not to be able to multiply. However, the regular capture of fertile – or diploid – grass carp and the discovery of herbivorous carp eggs in the Sandusky River in 2015 suggest that the methods used to sterilize these fish have not always been effective or that compliance with state regulations prohibiting fish from breeding was not complete. The exact number of grass carp in the Great Lakes is just a guess, but according to the U.S. Geological Survey`s database of non-native aquatic species, 30 fertile fish were caught in Lake Erie or its tributaries in 2016. Fourteen were captured in 2015, 25 in 2014 and only two in 2013. Habitat: The preferred habitat for grass carp is calm, shallow waters. When temperatures drop, deeper waters are used. Grass carp tolerate low salinity, so they can sometimes enter brackish water. The Michigan Department of Natural Resources is committed to preserving, protecting, managing, using, and enjoying the state`s natural and cultural resources for present and future generations. For more information, see www.michigan.gov/dnr. «There are still a number of states that allow what we call diploid grass carp to be used in their state waters, which means it`s a reproductively viable grass carp,» he says.
Studies have shown that grass carp caused a change in dominant local plant species a few years after it was introduced into a water body, the DFO report says. «Plants such as pond grass, mugwort, Eurasian watermilfoil and duckweed have disappeared, and poisonous plants and pesky hydrophytes have become more common.» Common: Common carp was introduced to the United States in the 19th century. Although it is an introduced species, it is not considered invasive. Many fishermen like to follow these fish in Michigan. (Photo by Michigan Sea Grant) The report`s authors note that there is a lack of published studies on grass carp movement in the New York Canal System, the Trent-Severn Waterway or between Lake Erie and Lake Ontario during the descent via Niagara Falls. Carp: Cleyo Harris, a fisheries biologist with the Michigan Department of Natural Resources, shows grass carp on Lake Erie. Silver: Silver carp, an invasive species, can grow to more than 3 feet and weigh up to 60 pounds. (Photo from the Great Lakes Fishery Commission) / Although they resemble silver and bighead carp in their reproductive and habitat needs, they differ in two very important ways. For more information on invasive species, including carp, see www.michigan.gov/invasives.
Grass carp feed on plants and consume up to 90 pounds of food per day. Fish can digest only half of the food and expel the rest, which contributes to algae blooms. Of the four invasive carp species on the watch list, bighead carp and silver carp are the biggest concerns. Don`t confuse young Asian carps with common Michigan species! – Brochure Grass carp can destroy seagrass beds used by native fish for spawning and rearing areas, and damage wetland ecosystems and waterfowl habitat. The Michigan and Ohio Departments of Natural Resources have launched a joint research effort with Michigan State University and Central Michigan University to better understand the status of grass carp in Lake Erie and develop effective management measures.
