The world's rarest fish doesn't live at the bottom of the ocean or in a remote Amazon pool. It lives in a clear, cool creek in Harford County, a few miles from where 1-95 crosses the Susquehanna River.

In 1912, two biologists noticed a fish they’d never seen before in Swan Creek; they named it the Maryland darter and published their discovery in a scientific journal. Fifty years would pass before the fish was noted again by graduate students in nearby Gasheys Run. Three years later, a healthy population was found in Deer Creek -- where all sightings since 1965 have occurred.

Scientists suspect the darter’s scarcity is due to its extremely specialized habitat requirements -- thriving only in that part of a stream where the water tumbles out of the hills onto the relatively flat coastal plain. The darter makes its home in the last riffles (fast-flowing areas) before the flatlands.

Historically, the Maryland darter may well have been more common to our western shore streams.  However, the influx of sediment, nutrients and chemicals from metropolitan and agricultural areas has degraded water quality and thus the specialized habitat.

As Maryland’s only endemic vertebrate – the only higher animal that lives here and nowhere else -- it is also an important indicator species, one whose presence or absence indicates the relative health of a natural ecosystem.

Illustration of the Maryland Darter
courtesy of Dr. David Neely

For more information:
The Maryland Darter