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Flying carp heading north

In a photo seen around the world, commercial fishermen George Richtman, Tim Adams and Bob Davis hold Asian carp caught March 1, 2012, in the Mississippi River. Richtman is holding a grass carp, Adams is holding a silver carp and Davis is holding a bighead carp. Both Richtman and Adams have worked on the St. Croix River in the past. Photo courtesy Nicholas Schlesser, Minnesota DNR

With the catch of a silver carp near Winona, Minn, by commercial fisherman, the concern about that invasive species has made headlines throughout the upper Midwest. What does this mean for the St. Croix River? To date, there have only been two Asian carp found in the St. Croix, one in 1996 and one in 2011 which were both big head carp.

A DNA test showed silver carp DNA in the St. Croix River below the St. Croix Falls Dam.

"The test is a presence or absence test," said Ron Benjamin, Wisconsin DNR fisheries supervisor on the Upper Mississippi River based in La Crosse. "The test just tells us that at some point in time a silver carp could have been there. All it tells us is the presence of silver carp DNA. The source is unknown. It could be from a fish, a carcass or another source but it does bring your attention up and you need to begin looking at this stuff."

Benjamin believes there is a small population of Asian carp in the upper Mississippi therefore it is reasonable that they would be in the Wisconsin and Minnesota border waters.

"We are not catching a lot but the Asian carp are expanding in the whole watershed," said Benjamin.

"We need the nation to implement a plan. These critters are not aware of state borders."

The Mississippi Interstate Cooperative Resource Association, MICRA, is an organization of 28 state natural resource departments. It was organized in 1991 as a partnership to improve management of interjurisdictional fish and other aquatic resources in the Mississippi River Basin. One of their biggest issues at present is the ongoing challenge of aquatic invasive species.

According to Benjamin, who is the current MICRA chairman, there was a national Asian carp plan adopted in 2007. It contained 131 recommendations. While 30 of them have been put in place by the Great Lakes area, the other 100 have been languishing.

"It is a very complex and difficult issue," said Benjamin. "People want a short and easy answer and there isn't one."

How did Asian carp come to be an invasive species? According to Benjamin, they were brought, mostly from China, to enhance catfish food in southern catfish farms. All three species of Asian carp were brought in. Grass carp, bighead carp and silver carp are each useful in their own unique way of clearing the farm ponds of organic and plant material. However, the ponds were low and subject to flooding, and the imported species began their march north.

As they move into the eastern South and North Dakota where a lot bait fish come from it raises new concerns.

"They all came from Asia but they can live anywhere in the continental United States," said Benjamin. "Now with the potential of them being included in bait buckets they are going to show up places they can't swim too."

MICRA acknowledges that most problematic AIS are bighead carp, silver carp, common carp but joining them are zebra mussels, Eurasian water milfoil, hydrilla, giant salvinia, Brazilian elodea, purple loosestrife, and water hyacinth. Other threats within the Mississippi River Basin that have the potential to cause large impacts in the future including species such as black carp, northern snakehead, didymo (rock snot), quagga mussels and the pathogen viral hemorrhagic septicemia (VHS).

MICRA's website indicates aquatic invasive species enter and spread within the United States through multiple pathways such as ship ballast-water discharge, canals and connecting waterways, escape from aquaculture facilities, aquarium and live bait releases, horticultural and water garden aquatic plant sales and use, attachment to barges and attachment to boats, trailers and other water/outdoor recreation equipment.

"We have to be rational in our approach but from the focus I have, the states really can't do much about it, whereas the federal government is the one that should take the lead," said Benjamin.

According to the website, the Mississippi River Basin is the fourth largest watershed in the world, and the largest watershed in the nation, draining all or part of 31 states and two Canadian provinces. The watershed measures approximately 1.2 million square miles, and covers 41 percent of the continental United States. The Mississippi River and its tributaries comprise one of the largest and most valuable ecosystems in the world.