"Last call for the Maryland darter. The elusive little fish, one of the rarest in the world, hasn't been seen in 21 years. Now, government and university biologists are teaming up for one more, perhaps final search for it in Harford County, where it's never been spotted more than sporadically since it was first noticed almost a century ago in a fast-flowing creek near Havre de Grace.
Named for the only state in which it's ever been found, this bottom-feeding member of the perch family has been seen in just three creeks off the lower Susquehanna River. No one has spied more than a handful of them at any one time since the 1960s. Repeated efforts to locate them in the past two decades have come up empty-handed."