ently joined Herrington, Auburn University research assistant Chase Katechis and Georgia DNR biologist Travis Ingram to catch and tag Alabama shad in the Apalachicola River, one of the largest rivers in the region.
As the team netted shad, I was able to see them up close: A plate-sized silvery fish that looks like it belongs in the ocean — and indeed, for much of its life it lives somewhere in the Gulf of Mexico (even scientists don’t know exactly where). In saltwater, it bulks up on other fish, but little else is known.
Come spring, shad surge up rivers like the Apalachicola. They don’t feed, instead putting their energy into reaching suitable spawning areas, where they lay eggs and (scientists think) die. The young shad migrate back to the ocean, continuing the cycle.
It’s a journey fraught with peril, as the fish I held so dramatically attested: Nearly every shad contained gashes on its side — the work of the longnose gar, a somewhat unsettling predatory fish with a protruding snout full of sharp teeth.
Overhead, ospreys carried other fish off in their talons.
But those perils are nothing compared to the biggest obstacle: a large dam that sat just upstream of our anchored boat.
In a Lock, the Key to Solving the Shad’s Problem
The dam’s exact effect on shad population declines wasn’t well known: little documentation exists for historic shad runs. But one thing was clear: shad weren’t getting past the dam, at least not in numbers that mattered. Fisheries surveys in the 1990’s noted few if any shad above the dam.
“The dam isn’t going away. It provides power for thousands of people,” says Herrington. “Given that, how can we work with it? How can we get fish over it without any money?”
There seemed to be a ready-made solution: A boat lock.
It operates as any lock does. A boat enters the lock at the bottom of the dam, as a door closes behind it. The lock fills with water (six million gallons in this case), raising the boat to the level of the impoundment behind the dam. A door opens and the boat exits above the dam.
Why not move fish the same way?
The problem was, fish didn’t know how to enter the lock.
Dams can be noisy places. As we captured fish, it was easy to ignore the background hum of a dam in operation: machines running, electric lines buzzing, the clanking of metal. For fish, though, it’s downright disorienting. How could they possibly figure out where to enter a lock?
Shad, it turns out, orient themselves on their migration through audible cues as well as river currents. The sound of running water is the sound of home. They instinctively follow that. There’s no sound of running water in a lock, especially when the door is open, at least not until now.
Enter the PVC pipe and water pump: the conservation equipment available for purchase at a home supply store near you.
The generator pumps water through the pipe, which is located above the lock. The water coursing through there sends a stream of water cascading into the lock below. It creates a loud splash. To fish, it’s like a road sign, or perhaps an old familiar song on the radio that takes you back to your youth.
The fish enter the lock, the water is raised, and they’ve successfully negotiated the dam.
Biologists like Herrington know this because they are catching fish and fitting them with radio transmitters, then tracking their movements. The fish are definitely entering the lock.
But there’s one other problem. “This is a very low use lock,” says Herrington. “Barges used to go through here regularly, but now there may be one or two a year.”
There are recreational boaters and anglers moving through the locks, but even then it may only be a couple of dozen lock passages a month—not enough to ensure consistent passage for fish.
Fortunately, the Army Corps of Engineers staff — who operate the lock — have agreed to run water and operate the lock twice per day when the fish are making their spring migration. Due to radio tracking, biologists know when the shad are most likely to be gathering at the dam ready to move (early morning and early afternoon), and that’s wh