Friday, August 23, 2013

Asian Carp Species Found 20 Miles Farther Upstream on Mississippi River Than Previously Observed

Silver carp
The Minnesota Department of Natural Resources (MN DNR) announced on August 22 that it's staff observed the carcass of a silver carp on a concrete abutment just below Mississippi River Lock and Dam 5, about 20 miles farther upstream than the previously northernmost instance of the species. Silver carp is one of four non-native Asian carp species threatening the Upper Mississippi River and other North American aquatic ecosystems. The other three species are bighead, grass and black carp. MN DNR scientists speculate that the silver carp found on the abutment was attempting to jump over the lock and dam structures. Such structures provide a partial physical barrier restricting fish passage along waterways. However, when locks are opened to facilitate river navigation, fish can more readily move up or downstream. Lock and Dam 5 is about 110 miles south of the northernmost lock and dam facility on the Mississippi River (Lock and Dam 1 in St. Paul, Minnesota), and three more lock and dam pairings lie between those two.

Silver carp can reach 60 pounds in weight, and impact the base of the aquatic food chain by consuming large amounts of plankton that some native fish also rely upon. To date there is no evidence that bighead or silver carp are reproducing in Minnesota waters of either the Mississippi or St. Croix rivers. However, established populations of both species are present in the Mississippi River and its tributaries downstream of Lock and Dam 16 in Iowa. Bighead carp have been found in Lake Pepin on the Mississippi River and in the St. Croix River in Minnesota, and as far north as the mouth of the St. Croix River in Prescott, Wisconsin.

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