They don't need current, they were introduced into catfish ponds. They took the place of German grass carp that didn't do good in the hot south. Their movement went east, west and north from SE MS. Catfish ponds in IA, KS, OK, IL, TX, IN, MN, MO, KY, TN, AR, LA along with MS had them when the great 75 year flood happened that flooded most every catfish pond that drains into the MS river system.