By Matthew Miller
Standing on the bow of the boat, Steve Herrington exuded the excited energy of a kid reeling in his first fish. Or perhaps a more scientific version of the Crocodile Hunter, bubbling with intensity. Net in hand, he scooped up shad — a migratory fish species — quickly examining them before passing them off to fellow researchers.
Last year I spent a day with Steve on Florida’s Apalachicola River looking at Alabama shad, a fish that researchers hoped would benefit by a practice known as conservation locking—basically allowing fish to pass through dams by using the same lock system that enables ships to pass.
At the time, conservation locking on the Apalachicola seemed to hold great promise for shad, a migratory species. He estimated that conservation locking could result in a returning population of 60,000 to 75,000 shad, indicating a steady increase.
Fast forward a year later. Herrington is on the phone, and that same infectious enthusiasm is literally bubbling over. “Great news!” he exclaims.
And indeed, his research has yielded surprising results. Those initial estimates of 60,000 shad? Way low. Estimates now showed a 122,000 fish increase, with as many as 280,000 total shad now in the system.
“We can now confidently say that conservation locking works, and we’re seeing a substantial bump in the population,” Herrington says. “I don’t know that there are any other data out there that so convincingly demonstrates such effectiveness.”
But how do researchers know this huge fish increase was related to the dam passage? Couldn’t the fish just be spawning below the dam?
The research has those questions covered, too. Part of the project was analyzing otoliths—the ear bones in fish—to determine where fish were born. Otoliths are like a tree’s rings, showing each year of a fish’s life. These rings incorporate trace chemicals of the waters where the fish have lived, enabling researchers to accurately track where a fish was born.
The results of the analysis: 97 percent of the shad population was born upstream of the dam.
The shad were passing the dam. They were breeding. And thriving.
Alabama shad once migrated in huge numbers up many southern rivers, and as far north as Iowa. Could conservation locking help restore Alabama shad more broadly across their range? Herrington has high hopes, and is currently working with other conservationists and the U.S. Army Corps of Engineers in ensuring low-tech, low-cost practices like this are authorized.
“There are rivers where shad still run, but they eventually bump their heads into a dam and can’t go farther,” Herrington says. “We have a simple way to provide effective fish passage.”
Shad once played a huge role in river ecosystems. A return of their numbers could have implications for other species. Freshwater mussel populations, for instance, have declined precipitously. Many mussel species begin their larval stage by living in fish gills, and there is some indication that some might require shad. Could more shad mean more mussels?
Similarly, young shad might provide more food for largemouth bass. In this part of the country, bass fishing is often mentioned in the same reverent tones as religion. Could more shad mean more and bigger bass?
These and other subjects are all subject to ongoing research. “We’re gathering data that show how the recovery of shad can lead to the recovery of mussels and recovery of ecosystems, and benefit the region’s recreation and economy,” says Herrington, formerly director of freshwater programs for The Nature Conservancy’s Florida program and currently filling the same position with Missouri.
And there’s still work to be done: despite the great success of conservation locking, only about 35 percent of shad are able to pass through. “We’re making the best of the situation. We are seeing large increases in population when 35 percent can get through,” says Herrington. “Just think what the population boost would be if we could get 60 or 70 percent through the dam.”
Herrington and other conservationists are now intent on working with the Corps of Engineers, who regulates these dams, to demonstrate how little tweaks in operations—like conservation locking—can make big difference for fish.
“This has been a really exciting year,” he says. “The results have far exceeded our expectations. This could be a real turning point for shad conservation, and for restoring migratory fish to our rivers.”
Success at the Woodruff Dam resulted in the same technique being used at two Corps dams on the Alabama River system, again with promising results. Lock gates were opened hundreds of times during spawning season at Claiborne Lock and Dam and Millers Ferry Lock and Dam, offering species like striped bass, mullet, paddlefish, and others access to spawning and feeding grounds that had been blocked for nearly 40 years.
“This is a welcomed effort to reestablish the great runs of fish that once swam over 350 miles from the Gulf of Mexico, through the Alabama River to the upland streams of the Cahaba,” said Paul Freeman, aquatic ecologist with the Conservancy’s Alabama program.
The Conservancy supported researchers from Auburn University, Alabama Department of Conservation and Natural Resources, and other partners to determine how to attract the greatest variety and number of fish possible into these two locks.
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With more than 600 dams across the nation, the Corps is the nation’s largest water management agency. Since 2002, the Conservancy has partnered with the Corps on dozens of dams to adjust operations and help restore natural river flow patterns.
Leveraging its successful partnership into a permanent, national program would benefit tens of thousands of miles of the nation’s rivers.
“We look forward to continued work with the Conservancy and the other agency and university partners as we explore these options,” said Brian Zettle, a biologist with the Corps.
U.S. Army Corps of Engineers
U.S. Fish and Wildlife Service
U.S. Geological Survey’s South Carolina Cooperative Fish Research Unit at Clemson University
National Oceanic & Atmospheric Administration
Florida Fish and Wildlife Conservation Commission
Georgia Department of Natural Resources
Alabama Department of Conservation & Natural Resources
University of Florida
Geological Survey of Alabama
The Nature Conservancy
May 06, 2013