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DNRE Prepares for Asian Carp Invasion

December 29, 2010

Asian carpBy now, there probably isn't anyone in Michigan who hasn't heard about Asian carp. The exotic imports, which have dramatically altered ecosystems wherever they've been allowed to become established, are mere miles from Lake Michigan and fisheries managers are worried about drastic environmental consequences should they find their way into the Great Lakes.

Michigan is concerned about four species of Asian carp - bighead, silver, grass and black carp. Of those, the silver and bighead present the biggest immediate threats.

Both species grow to be large fish that feed on plankton, the underpinnings to the aquatic food chain. Fisheries officials believe they could drastically alter the food chain in the Great Lakes and, because both species are capable of spawning several times a year, ultimately out-compete native species for habitat.

Bigheads are capable of reaching 80 pounds and can consume up to 40 percent of their body weight per day. Silver carp, which can reach 40 pounds, regularly jump out of the water when disturbed by vibrations from boat wakes or jet skis and are capable of causing significant injury to recreational boaters. In areas where these species have become established, recreational fishing has suffered significantly. Where silver carp have become established, recreational boating has declined drastically as well.

Asian carp were imported into the southern United States by the aquaculture industry to help control algae in ponds. Because of flooding, the fish escaped their ponds and became established in the Mississippi River drainage.

Asian carp have spread into the Chicago Sanitary and Ship Canal, a man-made canal that links the Great Lakes to the Mississippi River. The U.S. Army Corps of Engineers has built electrical barriers in the canal, designed to stop the progress of the carp into the Great Lakes. However, recent environmental DNA testing indicated that the carp might have breached the electrical barriers. (Environmental DNA shows evidence that the carp have been present because fish leave their genetic markers behind when the lose scales or slime or they defecate.)

In addition, at least one bighead carp has been collected in Lake Calumet, which is beyond the electric barrier, about five miles from Lake Michigan.

Great Lakes states attorneys general have filed lawsuits in federal courts, demanding that the locks on the Chicago waterway be closed to prevent further migration of the carp. Those suits, so far, have not been successful. The federal government has appointed a carp czar who is studying the situation, though a final determination of what is to be done to prevent further spread of the fish will not be made for at least a couple of years.

Michigan's Department of Natural Resources and Environment has been proactive on the Asian Carp threat, joining the Illinois Department of Natural Resources in a large-scale rotenone treatment of the Chicago waterway, sending three fisheries crews with boats and the department's inventory of rotenone - a chemical that kills fish by causing them to suffocate - to Illinois in 2009. The action turned up one dead Asian carp, though fisheries officials say more may have sunk and not been recovered.

In addition to participating in the rotenone treatment, the DNRE has begun sampling for Asian carp eDNA in the rivers in the southern part of the state flowing into Lake Michigan. So far those samples have not detected the presence of Asian carp. Silver carp have a habit of jumping out of water when disturbed by a wake, creating a dangerous situation for boaters.

In October, the DNRE unveiled an initial new plan for dealing with Asian carp in the Michigan waters of the Great Lakes. Neither a rapid-response plan nor a long-term management strategy, the plan maps out what steps the DNRE should take to address the potential environmental nightmare should Asian carp find their way into Great Lakes waters.

The plan seeks to answer the most obvious, immediate questions such as:

  • What does the Department need to do to adequately address the threat of Asian carp species invading Michigan waters?

  • What sampling strategies are appropriate in addressing this threat?

  • What should our response be if Asian carp, either isolated individuals or abundant populations, are detected in Michigan waters?

  • What are the pros and cons of various possible management strategies?

  • What types of resources (both financial and human) are necessary to adequately address this threat?

The plan has been posted on the DNRE website at www.michigan.gov/asiancarp.

In addition, the DNRE hosted a workshop on Asian Carp prevention in November, which brought in experts from the Great Lakes states, the federal government and Canada, to compare notes of prevention strategies.

No one is certain what might happen should Asian Carp find their way into the Lake Michigan Basin. Although some are optimistic that the big lake would prove too cold to allow the fish to become established, they exist along the same latitudinal gradients in Asia. And some of the river systems in which they have become established are similar to rivers in southern Michigan.

But fisheries officials don't want to gamble on what might happen, preferring to do whatever is necessary to prevent them from entering Lake Michigan.

Congress has appropriated funds to study control methods. But meaningful action appears to be years away.

Meanwhile, the DNRE is asking anyone who captures or observes what they think are Asian carp to report the incident by calling the Fisheries Division (517-337-1280) or filling out a report form online.

Asian carp are just one example of the potential problems caused by the unintentional translocation of aquatic species. Recreational boaters and anglers should take all precautions to prevent transferring organisms from one body of water to another. Live wells and bilges should be drained every time a boat is removed from a body of water and disinfected before the boat is returned to the water. And leftover bait should be disposed of on land, not dumped into the lake or river.

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