Sportfishing could be affected, agency says
Five Asian carp found in the lower Wisconsin River below the dam at Prairie du Sac are big, slippery evidence of how important it is to follow rules aimed at preventing the spread of invasive species, the state Department of Natural Resources said Wednesday.
Prevention includes notifying the DNR about any Asian carp that are caught, said Bob Wakeman, spokesman for the department’s aquatic invasive species program.
Wakeman said the Asian carp found this fall aren’t the first in Wisconsin waters, and they appear to be an isolated group that strayed from established populations south of Wisconsin in the Mississippi River.
“They are very mobile,” Wakeman said. “(Scientists) tracked these fish and one of the things they’ve discovered is they can put on a lot of miles in a short period of time. Doing a hundred miles is really nothing for them. (Asian carp) are big fish and they can zip up and down that river without much trouble.”
The carp are a threat to sportfishing because they are voracious eaters that tend to outcompete other species while altering aquatic ecosystems. Typically, they run from 10 pounds to 40 pounds, but can grow as big as 100 pounds.
One type — the silver carp — can be a hazard to anyone in a boat. When agitated by things like boat motors, the silver carp jumps high out of the water. They have slapped boaters, broken speedboat windshields and damaged bass boats.
The other types are grass, black and bighead. Bigheads were the type found by the DNR in the lower Wisconsin River. Fisheries workers counting sturgeon caught four big head carp and found another dead on the riverbank.
Bighead and silver carp can eat 5 percent to 20 percent of their body weight in plankton daily, the DNR said. Black carp consume primarily mollusks, threatening native mussel and sturgeon. Grass carp wipe out plant beds that are crucial habitat for young game fish and invertebrates that are important to fresh water systems.
Asian carp have made their biggest mark in waters south of Wisconsin.
“In the southern waters they can make up about 90 percent of the biomass of the fish in those tributaries,” Wakeman said. “We all like to fish and catch walleye and bass and all the other fish that the river supports. That loss would be pretty devastating.”
A dam and lock structure on the Mississippi south of the Wisconsin River seems to be an obstacle most of the fish aren’t crossing, Wakeman said. And some scientists believe the weedy pools of the Upper Mississippi River may be inhospitable to establishment of Asian carp because the water is relatively free of algae and there is ample competition from game fish, he said.
“People need to be aware,” Wakeman said. “If they are fishing and they happen to catch one of these, we would really like to get our hands on them.”
Asian carp have been captured from time to time in the lower Wisconsin River and Wisconsin’s stretch of the Mississippi since 1996. Bigheads have been found near the Prairie du Sac dam at least five times since 2011, the DNR said.
They were imported to the southern United States in the 1970s to help clean water in ponds used by fish farms and wastewater treatment facilities. Flooding carried them into the Mississippi River system.
Fisheries biologists are trying to learn more about the Asian carp. They can examine a specimen to gain knowledge about things such as where it originated, Wakeman said. It’s illegal to transport live Asian carp in Wisconsin.
Boaters and anglers can prevent the spread of aquatic invasive species by draining and cleaning boats after they come out of the water, disposing of unused bait fish in trash, and not transporting live fish that have been caught, Wakeman said.