© 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.
Beginning Monday, Van Sommeran received several phone calls from people who had seen leopard sharks stranded or dead in tide pools and sloughs just south of Foster City.
Catherine Greer and her 13-year-old son, Lorenzo Fernandez, were among the first to observe the ailing sharks. Fernandez arrived Monday to go fishing at a lagoon near Seabrook Court on the east side of Redwood City and saw distressed sharks near the shore, some of them coming out of the water and seemingly gasping for air. For the next two days the pair returned to find more weakened and beached sharks - around a dozen in all, ranging from 12 inches to nearly 4 feet long.
"They were resting their chins in the dirt on the shoreline, like they were trying to swim ashore," Greer said. Lorenzo "tried putting one back in the water, but it just came back and stranded itself."
Leopard sharks, which commonly grow to 5 feet long and live 40 years or more, are plentiful in the shallow coastal waters from Oregon to Mexico. They typically eat crabs, small fish and "innkeeper" worms. But their status as bottom-feeders means their systems can become saturated with harmful contaminants like mercury, pesticides and flame retardants that sink to the bay floor. Still, they are a pretty hardy species, usually the "last to abandon an ecosystem," Van Sommeran said. "They've specialized in doing well in hard-to-live-in areas."
That's why Van Sommeran and other experts are perplexed by several large die-offs within the last five years. Field researcher Brandy Faulkner of Palo Alto said that in 2006 and 2007 she documented dead leopard sharks "every 10 feet" along the bay at Coyote Point and Oyster Point.
Stanford University necropsies of similar but less common salmon sharks - which are increasingly washing ashore in California - showed some were infected with a pernicious bacteria that attacks the brain and leads to blindness, disorientation and, finally, paralysis. The leopard sharks observed this week showed the same problems, but the bacteria have not yet been detected in that species.
Van Sommeran theorizes that pollution may play a role. He and Faulkner point out that agribusiness giant Cargill, which operates 9,000 acres of salt evaporation ponds in the southern part of the bay, had four spills of bittern - a noxious salt production waste fluid - between 2000 and 2006.
State records show the company spilled 218,000 gallons of the substance in August of 2006, killing about 200 fish and resulting in a fine of $228,000. The salinity of bittern is about 10 times that of ocean water.
Officials at Cargill were not available to comment on Thursday.
Van Sommeran said he will continue to monitor the situation in the Redwood City area and work with officials at Stanford, the state Department of Fish and Game, National Marine Fisheries Service and U.S. Coast Guard in an effort to figure out what is killing the sharks. "It's not a crisis at this point," Van Sommeran said. "But we don't know what's going on for sure because no one dives for shark remains - we can only track those that beach themselves.
E-mail Kelly Zito at kzito@sfchronicle.com.
That's not a good PR department or not one being allowed to do their job of covering up the truth, which is usually the fearful ignorance of their corporate bosses who aren't used to being tested along these lines.