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Technology Center Helps Endangered Darter
by Craig L. Springer
US Fish and Wildlife Service
Craig_Springer at fws_gov
The Comal River in central Texas begins rather abruptly, gushing forth clear, 74_F-water from fissures at several thousand gallons per second. This stream is unique in many ways, but perhaps its most intriguing endowment is the fountain darter, a fish now in danger of extinction.
The historic large volume and steady flow of the Comal River creates habitat for the rare fish--and unfortunately, habitat for a non-native snail, the red-rimmed melinia, and its accompanying parasitic trematode (flatworm).
The trematode parasitizes the fountain darter, manifesting itself as cysts in the gills. This may sound like bad news, but since biologists only recently discovered the trematode, they are unsure of how it may harm the fountain darter.
Taking no chances, aquatic biologists at the national fish hatchery & technology center in San Marcos, Texas, are staying atop the learning curve with respect to fountain darter conservation.
Fountain darters live in the Comal and San Marcos rivers. Right now only Comal fish seem to be impacted by the trematode, said Dr. Tom Brandt, the centers acting director. Luckily, the parasite has only turned up in two San Marcos River darters. But what the parasite means for the security of the species, we just dont know yet. Its certainly something were very concerned about.
So concerned in fact, the center directs scientific inquiries into this very question. Collaborating with Melissa Salmon of Southwest Texas State University and Drew Mitchell of U.S. Department of Agriculture-Stuttgart National Aquaculture Research Center in Stuttgart, Arkansas, the Service may soon understand the impact of the trematode infestation.
Though studies are just in preliminary stages, university researchers use the centers expertise and facilities to investigate how the fountain darter, encysted with trematodes, reacts to reduced oxygen levels in the water.
Meanwhile, the center maintains a standing stock, or refuge population, of fountain darters on site. Should the worst happen in the wild--a chemical spill or drying of the springs that serve as darter habitat--the station holds more than 500 adult darters at any given time for future restocking.
Holding darters in captivity, has been a blessing in disguise. Keeping the refugium population under the watchful eye of biologists has led to ancillary benefits. These adults produced over 10,000 young fish last year, and these were used for several studies.
The longer we have darters on station, says Dr. Brandt, the more we learn about their biology. In the end, were better equipped to deal with threats that may arise with darters in the wild.
Some very serious threats challenge the fountain darter, but with the capable help of university, state, and federal biologists this native fish may someday be removed from the endangered species list.