The sight of millions of dead anchovies floating in a marina just south of Los Angeles has left fishermen and harbour chiefs puzzled about their death.
Experts have suggested that the dead fish, found at a harbour in Redondo Beach, may have died from lack of oxygen due to algae, while locals wondered if high winds overnight might have something to do with it.
"It looks like what happens to goldfish when you don't change the water in the tank, mouth open and belly up," the Daily Telegraph quoted local official Bill Workman as telling the Los Angeles Times.
"There are no visible signs of any toxins that might have caused (the deaths) and our early assessment is that this was oxygen depletion. There are no oil slicks or leaking of substances into the water," he stated.
Locals at Redondo Beach, where the stench from the dead fish hung over King Harbor, suggested that high winds could have driven the fish into the harbour, where their sheer numbers would have reduced the oxygen available.
Researchers have measured critically low oxygen levels in Redondo Beach's King Harbor after a massive die-off in the city's marina.
Brent Scheiwe, program director at the SEA Lab in Redondo Beach, about seven miles south of Los Angeles International Airport, said he took dissolved oxygen level readings in the harbour after the first reports of the dead fish came in and found them at almost zero.
"The levels were critically low. There was pretty much no oxygen in the water," he said.
Scientists are working to determine what caused oxygen levels to drop so steeply that fish estimated to be in the millions suffocated and deposited a silver sheen of carcasses, many of them sardines, among the rows of docked boats.
Marine biologists at the University of Southern California installed oxygen sensors in King Harbor after an algal bloom caused a mass fish die-off in 2005.
Biological sciences professor David Caron said they are now probing the harbour for clues about the cause of the latest kill.
"What we're trying to tease apart is whether it's a consequence of algal build-up, a fish build-up or something toxic in the water," Caron said. (ANI)