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US Fish & Wildlife Service FieldNotes

DON EDWARDS S.F.BAY NWR: Leopard Sharks Return Signals Success of Wetland Restoration Project

Region 8, September 23, 2013
Researcher Amy Chandros, U.C. Davis, with one of the leopard sharks captured for study, and subsequently released, in the south San Francisco Bay.
Researcher Amy Chandros, U.C. Davis, with one of the leopard sharks captured for study, and subsequently released, in the south San Francisco Bay. - Photo Credit: n/a

By Doug Cordell

“It’s a sign that the restoration work we’ve been doing is paying off.”

That’s Eric Mruz, manager of the Don Edwards San Francisco Bay National Wildlife Refuge, talking about the sudden flourishing of leopard sharks in the south San Francisco Bay and what it means for the historic South Bay Salt Pond Restoration Project.

The project, the largest of its kind on the West Coast, has been restoring former commercial salt ponds around the bay to tidal wetlands and managed ponds since 2008. The increased presence of the leopard sharks, documented recently in a study by researchers at the University of California, Davis, is a big indication that the restoration is having benefits.

"This tells us the water quality is getting better,' says refuge manager Mruz. "And it shows that these former salt ponds are providing tremendous amounts of fish, worms, crabs and other species. It tells us the South Bay is getting healthier."

Refuge staff and independent researchers have already documented the return of great numbers of birds and fish to the South Bay since the onset of restoration work. But the presence of the leopard sharks and other large predators, such as bat rays (which, incidentally, pose no threat to humans) is a particularly strong indicator that the natural area is rebounding.

The U.S. Fish and Wildlife Service is a partner in the South Bay restoration project, a first step in an effort to restore 100,000 acres of tidal wetlands around San Francisco Bay. Over the last 150 years, about 85 percent of the historic wetlands around the bay have been lost to development and agriculture. The results have been reduced wildlife habitat, diminished water quality, and an increased risk of flooding.

Now, as the return of the leopard sharks tells us, those trends are being reversed.

Doug Cordell is the Public Affairs Officer at the San Francisco Bay National Wildlife Refuge Complex in Fremont, California.

Contact Info: Doug Cordell, 510-774-4080, doug_cordell@fws.gov