Newswise — Scientists at the Department of Energy’s Oak Ridge National Laboratory are taking a closer look at how sturgeon, a prehistoric—and now imperiled—group of fish species may better be helped to get around the dams that block their migrations.

Hydropower is a major renewable energy resource; around 84,000 dams across the U.S. harness the power of flowing water for clean energy. Although there is a goal to minimize the environmental impact of dams and water infrastructures through ongoing conservation efforts and engineering advances, the unique needs of sturgeon require special consideration while building fish passage structures.

Many of those dams, however, still impede the life cycle of sturgeon, a bottom-feeding fish that once inhabited nearly every major river system in North America. The fossil-like fish is currently facing degraded habitat, limited aquatic ranges and in some cases, the threat of extinction.

ORNL ecologist Brenda Pracheil studies how different turbines and dam infrastructures affect the safe-passage success of bottom-feeding sturgeon for DOE. “Sturgeon have lost up to 60 percent of their previous ranges,” said Pracheil, a co-author of a recent study in Fisheries magazine. “Sturgeon swim for long distances, sometimes for hundreds of miles, to lay eggs. In some cases, females that can’t get to spawning grounds will simply stop and not lay eggs at all.”

“Reconnecting habitat is crucial to protecting sturgeon species in U.S. rivers,” said ORNL’s Henriette Jager, lead author of the study. “They’ve lost up to 60 percent of their historical ranges despite upstream and downstream fish passage facilities in place at dams,” she said.

Jager, a theoretical ecologist, was invited to present her research modeling white sturgeon reconnection at a workshop sponsored by the Great Lakes Fisheries Trust. Wintry weather, however, had a surprise in store for the group of experts invited to speak about sturgeon passage. After the conference, a snowstorm grounded all flights from the airport.

Snowed-in for the evening, Jager and the other scientists started discussing the imperiled fish species. “Current passage facilities don’t take the bottom-oriented fishes into account. We wondered, if they did—would it help?” she said.

So began a review of fish passage facilities in major rivers across the United States. The ORNL ecologists combined forces with several state, federal and university biologists from across North America to figure out what impedes sturgeon passage and survival.

Sturgeon are particularly vulnerable because they swim along river and lake beds, dragging sensitive whisker-like organs called barbels along the bottom to sense the terrain. They have trouble accessing fabricated fishways made to help other species swim past dams—a dead-end for the ancient fish.

The team analyzed seven fish transportation systems in place at various dams and waterways that get fish from point a to b.

In steep coastal rivers, for example, an escalator fish lift traps and raises fish upstream where they can reproduce. In the Midwest, nature-like fishways around low-head dams work well for sturgeon.

ORNL models contributed to the collaborative effort in understanding when and how reconnection of river segments is beneficial to sturgeons. Prior studies led by Jager used individual-based population models and helped the team determine how bottom-feeding sturgeon respond to current dam fish passage infrastructures.

Their review ultimately indicated the most effective passageways for sturgeon should include both upstream and downstream passage with entrances that are easily found and accessed by bottom-loving fish like sturgeon.

“The most effective passageways for sturgeon and other bottom-feeding fish species should include downstream guidance systems with bottom entrances or deep spillways,” Pracheil said, explaining that most entrances to existing passage facilities are neither large enough nor flush with the river bottom.

“Sometimes, relatively simple solutions can help sturgeon to navigate passage facilities,” Jager said.

Jager and Pracheil point to large-scale, collaborative research as valuable because it contributes to a cumulative understanding of human impacts for better energy infrastructure.

“It’s about awareness,” Jager said. “Now that we know what challenges face river sturgeon recovery, we can take an adaptive approach to addressing these issues. Interacting with other researchers helps to spread the word about what works and what doesn’t.”

The paper, titled “Reconnecting Fragmented Sturgeon Populations in North American Rivers,” is featured in Fisheries magazine.

ORNL sturgeon passage research was supported by Idaho Power Company, Department of Defense and the U.S. Department of Energy’s (DOE) Office of Energy Efficiency and Renewable Energy, Wind and Water Power Technologies Program.

UT-Battelle manages ORNL for DOE’s Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time.—by Ashanti B. Washington