No, that's not the new cool thing the teens are saying (but maybe it should be :-). A gizzard shad (Dorosoma cepedianum) is a silvery fish often used for bait by fishermen. It is considered native the Great Lakes region, the St. Lawrence and Mississippi rivers, and many other regions down through Florida and Mexico, but has also been introduced in many parts of the U.S., including Lake Holiday in Indiana. According to the Indiana Post-Tribune, the resulting population explosion in that lake caused officials to commit to poisoning the lake with rotenone, beginning this week. You can read about similar problems with shad in Lake Powell, Arizona here.