Oct 04, 2011

Texas Drought Prompts Fish Rescue

The Double Mountain Fork of the Brazos River has been dry since May 2011, during a period of time that has directly overlapped with spawning season for sharpnose and smalleye shiners. Photo by Leaflet via Flickr.

By Eva Hershaw
For Reporting Texas

AUSTIN — Wildlife biologists have rescued nearly 3,000 sharpnose and smalleye shiners from the Brazos River, the only place they are known to exist, in a bid to save the fish from extinction during the Central Texas drought.

Scientists hope the fish, being held in the Possum Kingdom Hatchery in Grandel, can be reintroduced to the wetter lower Brazos later this month. “If water doesn’t return to the Brazos, this would spell the end for these species,” said Kevin Mayes, an aquatic biologist with the Texas Parks and Wildlife Department.

Of the many species suffering population decreases in the drought, the shiners of the Brazos have two characteristics that made their rescue a priority. First, the sharpnose and smalleye shiners are geographically limited to the Brazos River basin. Second, they have a life expectancy of just two years. After losing one generation to this year’s drought, the survival of both species depends on whether they lose another.

Biologists are concerned that the Brazos has the smallest amount of flowing water ever since the United States Geological Survey installed river flow gauges in 1923. The Brazos River Authority estimates the river is at 64 percent capacity. It’s normally between 80 and 90 percent at this time of year.

“In Northwest Texas, it is going to be dry, and the river is going to be low,” said Judi Pierce, the river authority’s public information officer. “But whether it’s a gully washer or a light rain, there’s usually something.”

Since May, the USGS gauge at Seymour has recorded almost no flowing water. “There’s never been a time in the past of five straight months at zero or near zero,” Mayes said. “And never did it overlap so perfectly with this spawning season, which runs May through September.”

Though shiners are only two inches long, they require 100 miles of flowing water to reproduce and rely on water currents to disperse fertilized eggs. Such fish cannot reproduce in a stagnant pool or reservoir.

Yet shiners are no strangers to adversity. Their bodies have evolved to weather drought conditions. They can tolerate increased water temperatures, low amounts of dissolved oxygen and have high salinity. The Brenham salt dome, which underlies the Brazos and causes its elevated salinity, is a living reminder that the Gulf of Mexico, now hundreds of miles away, once covered the basin.

“They’re just tough fish,” said Gene Wilde, a conservation biologist at Texas Tech University who work with the TPWD to rescue shiners.

The shiners are at risk from more than natural hazards. “When people say that we shouldn’t rescue the fish, that it’s natural selection, they fail to understand the connection between the condition of the river today and the condition of these fish,” Mayes said.

The three dams that interrupt the flow of the Brazos, and the reservoirs they have created as a consequence, have impaired the shiners’ ability to follow the water downstream in times of drought. “Dams create an effective barrier to passage and the creation of habitat,” Mayes said. Not only do dams act as a physical impediment to migration, they have also created ecosystems in which small fish such as the sharpnose and smalleye shiners become sitting prey to larger game fish.

To some, the case of the sharpnose and smalleye shiner is exemplary of the state’s mismanagement of Texas waterways. “It’s the challenge of balancing human needs for water with keeping our rivers, streams, lakes and bays healthy,” said Ryan Smith, a freshwater ecologist with the Nature Conservancy.

The plight of shiners could also signal the need for broader changes in water management in Texas. “The 1950-1957 drought set the standard by which we determine how much water is available for consumption,” Pierce said. “Depending on how long this lasts, we may adjust how our drought contingency plan prescribes the availability of water.”

For now, the biologists watching over the Possum Kingdom Hatchery can only hope for rain and do their best to get self-sustaining shiner populations into as many parts of the Brazos as possible. “If we don’t get it this year, we lose two unique species,” Wilde said. “And their demise would be a reflection of our stewardship of the Brazos River.”