In an article in the Naples News, Shawn Liston at Audubon's Corkscrew Swamp Sanctuary writes about the importance of Crayfish in measuring success of Everglades restoration:

South Florida wetlands are home to two different crayfish species that look remarkably similar, and their presence or absence provides information about wetland types. “Everglades crayfish” are found primarily in short-hydroperiod wetlands (wetlands that dry for several months each year) while “slough crayfish” are found primarily in long hydroperiod wetlands (wetlands that remain wet for most of the year). Biologists can learn a lot about wetland hydrology from crayfish, and they serve as important indicators of wetland health and the success of Everglades restoration projects.