Coon Rapids Dam serving to block potential spread of Asian carp
Attorney General Lori Swanson’s recent legal actions relating to the potential spread of Asian carp into the Great Lakes — she’s looking to clamp off waterways in Illinois to the exotic fish — is only one aspect of a larger challenge.
According to the Minnesota Department of Natural Resources (DNR), some seven species of Asian carp have been introduced to the United States.
Four of the exotic carp — the grass carp, black carp, bighead carp, and silver carp — often grace environmental publications.
These exotics, worrisome because of their feeding and reproductive gusto and the challenges they could present native fish, have already penetrated into the region.
A grass carp was caught in the St. Croix by commercial fishermen in 2006, and bighead carp have been caught in Lake Pepin.
According to a 2007 DNR study, no silver carp have been confirmed in Minnesota, though the carp has been found in the Mississippi River in southeast Iowa.
These carp are active and known for leaping from the water when disturbed, potentially imperiling boaters.
The study stated that there were no known populations of Asian carp in state waters yet — the individuals caught were pioneers, of sort.
Preventing Asian carp from infiltrating Minnesota waters presented a “daunting” challenge, the study concluded.
The window of opportunity for halting the migration into the lower Mississippi River in Minnesota by use of behavioral barriers — acoustic bubble curtains, for instance — was maybe closing.
Still, physical barriers in the river could prevent Asian carp from climbing the upper reaches.
St. Anthony Falls historically has been a natural fish barrier in the Mississippi River, for 10,000 years serving to block off the upper reaches until the river was opened to barge traffic in the 1960s.
Indeed, while some 123 fish species were known to inhabit the Mississippi below the falls in the past, just 64 were found above.
Currently, the venerable Coon Rapids Dam serves as a man made fish barrier, but should the dam be breached Asian carp could enter the Rum River at Anoka, potentially spreading upstream to Mille Lacs Lake.
The study suggested looking at possibly restoring St. Anthony Falls as a natural fish barrier.
Recently, a number of lawmakers mailed a letter to Swanson and the governor calling for state officials to renew action against the spread of Asian carp.
