DNA evidence of Asian carp above electric barrier grows
[It’s been awhile since Desdemona has had an update on this story; here are previous posts on the Asian carp invasion.] By Dan Egan of the Journal Sentinel
18 June 2012 While it’s been nearly two years since crews landed the only live Asian carp specimen above an electric barrier on the Chicago Sanitary and Ship Canal, DNA evidence of the jumbo carp continues to come in – and the percentage of DNA-positive water samples taken above the barrier this year appears to have grown tenfold over last year. The Army Corps of Engineers reported that of the 2,378 water samples taken throughout 2011 in the canal system above the electric barrier, a total of 34 samples were positive. This year, after just one day of sampling the waters above the barrier, the Army Corps reports it landed 17 positive results from 114 water samples. In other words, the percentage of samples that tested positive for Asian carp DNA last year was about 1.5%. This year, so far, it has jumped to almost 15%. The information is posted on the Army Corps website. The electric barrier is about 30 miles downstream from the Lake Michigan shoreline, and 25 miles downstream from that barrier the waters are known to be home to a robust population of two species of Asian carp, bighead and silver. All of the positive samples taken above the barrier for 2011 and so far this year have been for silver carp. The Army Corps maintains that a positive sample doesn’t necessarily mean evidence of live fish above the barrier. Efforts to contact agency officials on Monday were unsuccessful, but in the past they have speculated that the DNA material, mere molecules, could be coming from barges carrying contaminated bilge water past the barrier, or from a fish that flopped onto a barge deck and was then carried through the barrier, or from the feathers or excrement of birds, or from restaurants in the Chicago area that serve Asian carp raised or caught in waters outside the Great Lakes basin. […] The University of Notre Dame researchers who helped pioneer the DNA sampling agree that some Asian carp DNA likely has gotten beyond the barrier by means other than a live fish, but they say the overall pattern of positive samples during the three years of testing the canal waters is powerful evidence that at least some live fish are now swimming above the barrier. Most of the recent positive samples were taken from Lake Calumet, a water body about six miles south of Lake Michigan but one with a direct hydrologic connection to the big lake. “Whoa,” said Thom Cmar, an attorney with the Natural Resources Defense Council, when shown the number of positive hits taken from the May 22 sampling trip. […] “This is the third summer we’ve seen positive eDNA hits in Chicago, and the third summer that the Corps says it needs more time to act. A real solution has to move faster than the carp,” Cmar said. “Seventeen eDNA hits in one day suggests that isn’t happening.”
