For a foot-long fish that depends on both saltwater and freshwater to survive, a massive lock located on the border between Florida and Georgia is proving to be the key to its future.
The Jim Woodruff Lock and Dam is a hydroelectric dam on the Apalachicola River in Florida, which connects the Gulf of Mexico to the Chattahoochee and Flint rivers in Georgia. Constructed in 1952, the dam created a migration barrier for Alabama shad and other migratory fishes, which swim upstream from the Gulf to as far north as Missouri to spawn.
This now globally rare fish is getting help from conservationists to make sure it reaches its spawning grounds. The Nature Conservancy worked with the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, National Marine Fisheries Service, Florida Fish and Wildlife Conservation Commission, and Georgia Department of Natural Resources to devise a simple plan that uses the lock at Jim Woodruff Dam to help the Alabama shad pass upriver in the exact same way the dam passes barges and boats.
Before 2005, the locks were used infrequently because ship passages had become rare. Now, during the spawning season each spring, the locks to the Apalachicola River - where the largest known population of Alabama shad is located - are opened at least twice each day for fish passage. The locks are opened the same way they operate for the passage of ships, except that a simple water pump is used to attract fish into the lock.
“Conservation locking” provides Alabama shad access to more than 150 miles of historic fish spawning grounds at almost no additional operation costs to the dam. In the last eight years, Alabama shad populations have increased four-fold and research proves that 89 percent of these fish were spawned upstream of the Jim Woodruff Lock and Dam.
Dr. Steven Herrington’s research has followed the Alabama shad’s migration upstream. He began protecting the shad for the Conservancy in Florida in 2005 by working with partners at the Jim Woodruff Dam to implement conservation locking. Then Dr. Herrington followed the fishes to Missouri to study otoliths, small bones in their inner ear that tell scientists much about the life cycle of the shad.
“Otoliths have annual growth rings, like trees, that offer clear evidence that Alabama shad are using the lock to reach historical spawning grounds in the Apalachicola River Basin,” said Dr. Herrington, now the Missouri Director of Freshwater Conservation for the Conservancy. Conservation locking is working to reconnect vital habitat for the Alabama shad and is also benefitting other species that depend on this fish for survival.
For example, baby freshwater mussels must attach themselves to the gills of fishes for a period of time before detaching and settling more permanently on river bottoms. Researchers at the University of Georgia working with the Conservancy have discovered that mussels are attaching themselves to the recovering population of Alabama shad in the basin.
“Mussels need fish to complete their life cycle” said Herrington. “They also provide critical ecosystem services by removing contaminants and excessive nutrients from the water. In essence, mussels are living filters for rivers. Our findings suggest that recovering the once-numerous shad could help recover imperiled freshwater mussels in the Apalachicola and perhaps other river basins as far north as the Gasconade and Meramec rivers in Missouri.”
Alabama shad are also an important food source for sport fishes like striped bass and largemouth bass. Their recovery is expected to invigorate fishing on Lake Seminole, created by the dam, and on the Apalachicola River, where thousands of anglers provide a substantial revenue source for the region.
The success of conservation locking at the Jim Woodruff Lock and Dam prompted the Army Corps to implement identical projects at two other locks on the Alabama River, where migratory fish species were also in decline. With more than 600 dams in the United States, this low-tech, low-cost solution is an opportunity to help restore river health and biodiversity across the nation.
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