© Lance Iversen / The ChronicleA dying leopard shark thrashes around in a Redwood Shores slough. At least a dozen such sharks have been found.
At least a dozen leopard sharks have been found dead or dying within the past several days in bayfront lagoons in Redwood City, putting local researchers on alert for some kind of infection or toxic discharge in San Francisco Bay.
The deaths, including both juvenile and adult sharks, appear isolated and far less serious than previous die-offs in 2006 and 2007, which left shark carcasses strewn all over the bay, officials said. Shark experts fear there may be more of the strikingly patterned creatures floundering in Bay Area waterways and succumbing to pollution and disease.
"In the last decade, we've seen an increase in the animals trapped in culverts and pumps that used to be tidal canals or poisoned by periodic pollution events," said Sean Van Sommeran, executive director of the Pelagic Shark Research Foundation, a Santa Cruz group that tracks sharks in Monterey and San Francisco bays.