Scientists consider the Laurel Dace to be the second-most-imperiled fish east of the Mississippi River — among the top 10 nationwide — and is now found in just two streams on Walden Ridge.

A biologist from the Tennessee Aquarium Conservation Institute holds an endangered Laurel Dace during a population survey in 2020. This species is considered by biologists to be one of America’s ten most-endangered fish species. It now is found on Walden Ridge in just two streams, which are drying up due to exceptional drought conditions in Southeast Tennessee.  Tennessee Aquarium

These species are especially at risk during droughts since their ranges are already limited to just a handful of small, headwater streams, many of which now have drastically reduced or even nonexistent water flow.

When drought conditions persist for long periods, reduced water volume can cause a cavalcade of problems for fishes.

In large enough quantities, water is a stable thermal environment, being slow to lose or gain heat. Without the benefit of rainfall, streams with less water are more likely to swing wildly between nighttime and daytime temperature extremes, which can stress the animals.

The lack of aquatic real estate means less available oxygen and crowded quarters.

“Think if all your neighbors on your block all the sudden started living in your house with you — you’d be stressed,” he said. “Just the fact that all these fish bodies are in a small area is stressful.”

The list of problems include:

• Greater risk of predation by opportunistic anglers like wading birds and raccoons
• Fewer aquatic insects and other prey items fish rely on to fuel during spawning season
• Less genetically robust populations due to the loss of individual fish

It’s bad news on top of more bad news

“This is not a feel-good story,” Dr. Kuhajda said. “It’s just an almost impossible situation to manage, and it’s really rough on aquatic animals.”

“Exceptional droughts can inflict huge damage on these headwater species, especially endangered species with only a few populations left.”

In November 2016, Chattanooga and other parts of Southern Appalachia were parched during another exceptional drought. That event prompted a collaborative “rescue” of wild Barrens Topminnows and Laurel Dace by the Tennessee Aquarium Conservation Institute (TNACI) and U.S. Fish and Wildlife Service (USFWS).

Warren Stiles, left, of U.S. Fish and Wildlife Service and Dr. Bernie Kuhajda of the Tennessee Aquarium Conservation Institute use a seine net to collect endangered Barrens Topminnows out of a mostly dry stream during an exceptional drought in November 2016.  Tennessee Aquarium

The team drove to drought-ravaged sites in Middle Tennessee and atop Walden Ridge known to shelter the last remaining populations of these endangered fish. There, they carefully collected what individuals they could in hopes of safeguarding them until conditions returned to normal or to serve as an “ark population” in the event that the species went extinct in the wild.

USFWS and TNACI are now carefully monitoring these populations once again.

“We don't have a specific threshold for when we start paying attention to how drought is impacting headwater streams, but as the USDA’s U.S. Drought Monitor starts moving to higher levels, it comes to mind,” said Warren Stiles, a listing and recovery biologist at USFWS’s Tennessee Ecological Services Field Office in Cookeville, Tenn.

To keep tabs on these crucial sites, USFWS relies on making regular, in-person visits to evaluate populations and maintaining good relationships with land owners and state partners who can alert them to any changes. 

Last week when Stiles checked in on Laurel Dace and Barrens Topminnows in Middle and Southeast Tenn. Drought he found low, water flow; isolated pools still being fed by groundwater — but conditions had yet to reach a point where another rescue was warranted.

“Headwater streams are especially dependent on groundwater flow, which can be affected by withdrawals, but they sometimes can be surprisingly resilient to drought,” he said. “However, extended drought does continue to stress fish in isolated pools, and the warm weather contributes to that as well.”

Relief in sight? 

There could be a small measure of meteorological relief in the coming days. Scattered rain fell on Chattanooga over the weekend, and extended forecasts by NOAA indicate precipitation chances that are leaning above average for Tennessee, Georgia, and Alabama. 

“The ground is so dry right now that hardly any of the rain makes it to the stream,” Dr. Kuhajda said. “We’ll need some pretty significant, major rain events of several inches to get those waters flowing again. It’s getting to a pretty critical point now.”

These changes are welcome, but ending such a prolonged drought and restoring the flow to area waterways will take a steady stream of major precipitation events. If there is no significant change to rainfall patterns in the next few weeks, biologists will need to reassess the Barrens Topminnow and Laurel Dace streams again.