Biologists from the U.S. Fish and Wildlife Service, U.S. Forest Service and Oklahoma Department of Wildlife Conservation recently donned snorkel equipment to survey the federally listed leopard darter in several Ouachita Mountains streams.
Surveyors followed thorough protocol: Five biologists swam the length of the streams’ pool with snorkel equipment. Each biologist stayed on an invisible pre-determined transect or “lane.” As they swam their lane, each biologist counted the number of darter species seen as well as any fish species encountered. While the primary purpose of the survey was to record presence or absence of leopard darters, the secondary data allow for comparisons of the fish community from one year to the next.
Daniel Fenner, biologist with the U.S. Fish and Wildlife Service, has conducted the annual leopard darter survey for 12 years. “We try to survey the same 20 sites each year using the same biologists when possible. This helps limit observer bias in the data.” In addition to these permanent sites, the survey team also visits about 100 sites on a three to four-year rotation. But biologists weren’t able to survey all the sites scheduled for 2014. Late July rains increased stream flow and clouded the water, postponing the survey. Even with the delayed survey date, many of the traditional sites were too turbid, or murky, to successfully survey for the small fish that rarely exceed 3 inches in length.
Named for the dark blotches on its side resembling spots of a leopard, the leopard darter is considered among the country’s rarest fish. Curtis Tackett, wildlife diversity biologist with the Wildlife Department, said this fish is found only in the Little River drainage system in southeast Oklahoma and southwest Arkansas.
“Most of the year, leopard darters live in large, quiet pools. But in March and April, they use riffles, or shallow flowing water with gravel and cobble substrate, as spawning grounds.” During this time, the female lays an average of 65 eggs. While the eggs are being laid, a nearby male fertilizes them. The female darter uses her tail to bury the eggs immediately after fertilization. Young darters are first seen in May of each year.
Naturally rare, the leopard darter has encountered many challenges in the last 150 years. Several dams have been built during this time, converting much of the leopard darter’s stream habitat into large reservoirs. Matt Fullerton, endangered species biologist with the Wildlife Department, said “six major impoundments have been built within the Little River Basin, restricting this darter to the headwaters of these rivers.” Deteriorating water quality, due in part to increased pesticide use and land management activities such as logging and confinement agriculture operations, also poses a threat to the leopard darter. Fullerton said the fish has been protected by the Endangered Species Act since 1978.
To prepare for the two-day survey, participating Wildlife Department staff attended USFWS water safety training. Biologists practiced pulling fellow surveyors to safety using throw ropes, inflatable rescue sticks and personal flotation devices.
Watch biologists survey on Outdoor Oklahoma’s YouTube channel.
Jena Donnell or Micah Holmes.
Telephone: (405) 496-0350
Image courtesy U.S. Fish and Wildlife Service