Birmingham Audubon Society

The Watercress Darter: An Endangered Species

Watercress Darter

 
BAS is an Audubon Refuge Keeper for the Watercrss Darter National Wildlife Refuge near Bessemer.  BAS volunteers work with the U.S. Fish and Wildlife Service to protect the endangered watercress darter fish.   The Watercress Darter Refuge is located in southwestern Bessemer at the corner of Division Street and Eastern Avenue. The seven acre site contains two small ponds which are two of only 4 remaining ponds forming the remaining habitat of this endangered small fish.

The watercress darter is a member of the Etheostoma swaini species group, subgenus Oligocephalus. The species is approximately 2.5 inches in total length, and has bright red and blue lateral bars and fin color in the males. It is currently thought to be limited to Halls Creek, Thomas Spring, and adjacent spring runs in Bessemer, Alabama, and Roebuck Spring and its runs which are a tributary to Village Creek at Roebuck suburbs in northeastern Birmingham. Ground water flowing into Roebuck Spring already is known to be polluted by seepage from septic tanks, and pesticide runoff remains a threat. "Gas bubble disease" is affecting the Roebuck Spring population. High levels of coliform bacteria in Glenn Springs indicate some sources of pollution.

Two Watercress Darters

It is found in watercress-choked waters of lime-stone spring origin. It tends to avoid open stream areas and is predominantly associated with dense growths of watercress (Nasturtium officianale) and other aquatic plants. The darter is apprently vulnerable to predation as it is absent in springs with large populations of green sunfish, bluegills, and sculpins. The darters feed upon snails, crustaceans, and insect larvae that usually inhabit the springs and spring runs. The breeding season of the watercress darter (March-July) is more extensive than most stream-swelling darters, probably due to the rather constant temperature of the spring water.

The species receives protection in the Thomas Spring at the Watercress Darter National Wildlife Refuge in Bessemer, Alabama. Green sunfish and bluegills are likely to be preying heavily on Thomas Spring watercress darters. The Thomas Spring population was formerly reduced by introduced grass carp. Since removal of these fish and subsequent revegetation of the spring, recovery seems to be taking place.

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Pictures of the watercress darter are courtesy of Dr.W. Mike Howell, Biology Department, Sanford University, Birmimgham, Alabama. Dr. Howell helped discover the watercress darter in the 1960s when he was a graduate student.