There’s a back door for Asian carp to sneak into Minnesota, and fisheries officials are worried the invaders might have found it already. It runs through Iowa. Commercial fishermen recently netted dozens of Asian carp in northwestern Iowa’s Great Lakes. Those waters connect with lakes and streams in southwestern Minnesota, so the haul came as an unwelcome surprise. Officials believe the Asian carp reached East Okoboji and other lakes in the chain during record flooding last summer. No Asian carp have been caught in southwestern Minnesota so far. But the state has already begun taking defensive measures. Several lakes, rivers, creeks and drainage ditches in Jackson and Nobles counties are now designated as infested waters because of the risk that a vanguard of Asian carp might already be lurking there.