Biologists on the upper Mississippi River are making a last ditch attempt to save a little-known endangered species---a small, mud brown mussel known as the Higgins' eye. Hordes of non-native zebra mussels infesting the Mississippi have devastated native mussel populations---and nearly wiped out the Higgins eye. Now, scientists are trying to evacuate the Higgins' eye to tributaries of the upper Mississippi--- places free of zebra mussels where the native mussels can find refuge. Minnesota Public Radio's Mary Losure reports.