Rare, Threatened and Endangered Animal Fact Sheet

Maryland Darter

The world's rarest fish doesn't live at the bottom of the ocean or in some remote pool in the Amazon Jungle. It lives in a clear, cool creek in Harford County, Maryland, just a few miles from where 1-95 crosses the Susquehanna River. The fish is the Maryland Darter, Etheostoma sellare, named for the only state in which it has ever been found.

Illustration of Maryland Darter, courtesy of Dr. John Neely 


On a summer day in 1912, two biologists collecting fish in Swan Creek, a fast-flowing stream near Havre de Grace, Maryland, noticed a fish they had never seen before. They named the unusual find the Maryland Darter and published their discovery in a scientific journal. Nothing more was learned about the Darter until 1962, when a group of graduate students found one near Swan Creek in Gasheys Run. The discovery spurred renewed interest in the Maryland Darter, and three years later, a second Darter was found in Gasheys Run. Around the same time, a healthy population was found in Deer Creek. Further investigation in Swan Creek and Gasheys Run failed to produce any more of these Darters, although suitable habitat for this species still occurs in Gasheys Run. Since 1965, all sightings of the Maryland Darter have been confined to Deer Creek.

[Map of Maryland showing the area in the state the darter is found, Harford county in the Susquehanna River]

Why is this Fish so Rare?

Scientists suspect that the scarcity of the Maryland Darter is due to its extremely specialized habitat requirements. Maryland Darters seem to thrive only in that part of a stream where the water tumbles out of the hills onto the relatively flat coastal plain. The Maryland Darter makes its home in the last "riffles," fast-flowing areas, before the flatlands. The Service between the hills and the coastal plain is known as the "fall line." This is also the point at which ships can go no farther upstream. At one time, the Maryland Darter may have been common to many of the streams that flow into the Chesapeake Bay from the Western Shore. We will probably never know because the Maryland Darter's habitat is the point at which cities and towns grew and land was cleared for outlying farms. The influx of sediment, nutrients, and chemicals from these growing metropolitan and agricultural areas degraded water quality. This change in the Maryland Darter's habitat would have been a major shock to the Darter, reducing the population to the present remnant.

Why is the Maryland Darter Important?

The Maryland Darter is Maryland's only endemic vertebrate. This means that it is the only higher animal that lives in the State of Maryland and nowhere else. It is a living museum piece: a survivor from a different, more pristine Maryland, before human influence changed the nature of the land forever. These facts alone are ample justification for the preservation of this rare fish. Yet there is another, more practical and equally important reason for saving the Maryland Darter. The Maryland Darter is an "Indicator Organism," a species whose presence or absence indicates the relative health of a natural ecosystem. The continued existence of the Maryland Darter in Deer Creek indicates that this watercourse is still relatively healthy and clean.

Deer Creek is home to trout, bass, and many other important fishes, as well as birds, reptiles, mammals, and other wildlife. Its value as a recreation area is demonstrated by the thousands of people who visit the State Parks within its watershed. Since the only Maryland Darter population known to exist is located at the mouth of Deer Creek, it is subject to all of the changes occurring within the watershed. Thus, only by protecting the entire Deer Creek watershed, through careful management of land use, can the Maryland Darter's fragile habitat be maintained. By protecting the Maryland Darter, we also ensure that Deer Creek, a rare and precious aquatic resource, is maintained in good health.

What Can Be Done to Help the Maryland Darter Survive?

The Wildlife and Heritage Service of the Department of Natural Resources is implementing the Maryland Darter Recovery Plan. This plan recommends the protection of the Deer Creek watershed through the use of improved farming and forestry practices, and the propagation of strips of naturally vegetated lands adjacent to Deer Creek and its tributaries. These buffers will insulate the watercourse from harmful runoff from adjacent lands. The voluntary cooperation of landowners along Deer Creek, and the commitment of government agencies, may help the Maryland Darter survive.

The Importance of Buffers

A buffer is a band of natural vegetation that insulates a body of water from land disturbances such as farming, logging, or development. The buffer protects the watercourse by:

  • Filtering solid material from runoff

  • Absorbing excess nutrients and toxic chemicals from runoff

  • Preventing erosion of stream banks by providing leaf cover and root systems to hold the soil

  • Cooling the stream bed by shading it from the sun

Buffers also provide habitat for birds and other animals and serve as good areas for hiking, hunting and nature observation.

Establishing natural buffer areas along tributaries to the Chesapeake Bay is one of the most important components of the Bay cleanup effort. Deer Creek is a tributary stream to the Chesapeake and the vegetated buffer areas that protect the Maryland Darter and Deer Creek will help protect the Chesapeake Bay.

How Buffers Work

Runoff - Runoff from development, industry and farming contains sediment, excess nutrients, and chemicals. These materials cause changes in stream quality and degrade aquatic habitat.

Buffer - As runoff flows through the buffer, the natural vegetation filters out sediment and traps excess nutrients. The buffer also provides excellent wildlife habitat for many animals.

Stream Bed - Protected from sediment and nutrient impacts, the stream bed and the water remain clean. The shading effect of trees along the stream bed keeps the water cool.

For more information about the Maryland Darter please contact:

Maryland Wildlife and Heritage Service
Department of Natural Resources
Tawes Building, E-1
Annapolis, Maryland 21401
(410) 260-8540
Toll-free in Maryland: 1-877-620-8DNR, Ext. 8540


Text by Jonathan McKnight, Kathy Prendki, and Wayne Tyndall, Maryland Wildlife and Heritage Service. Illustration of Maryland Darter, courtesy of Dr. John Neely.

Funding and assistance provided by the U.S. Fish and Wildlife Service and the Fisheries Service of the Maryland Department of Natural Resources, Tidewater Administration.