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Massive fish die-off likely due to oxygen depletion, not pollution, Redondo Beach officials say [Updated]

March 8, 2011 | 11:24 am

Dead Fish Mystery

Redondo Beach officials said initial assessments suggest oxygen depletion in the King Harbor basins caused the massive fish die-off.

City Manager Bill Workman said city officials with the help of marine experts would help determine if there was any environmental issue involved. Tests are now being performed on the water as officials begin removing the dead fish, which city officials estimated to be in the millions.

“There are no visible signs of any toxins that might have caused [the die-off] and our early assessment is that this was oxygen depletion,” Workman said. “This is similar to what we experienced five years ago but that was distinctly a red tide event but there’s no discoloration of the water, no associated foaming in the waves, Workman said. “There are no oil slicks or leaking of substances into the water.”

Workman noted that the harbor had been teeming in recent weeks with bait fish that even after their deaths “had no signs of degradation.”

“It looks like what happens to goldfish when you don’t change the water in the tank, mouth open and belly up,” Workman said.

Although he said it did not appear that the die-off was due to a red tide, the city diverted all of its city crews to the harbor to help with the response to the fish kill by bringing in dumpsters and nets.

Workman also said the city was preparing to call in volunteers to assist with the cleanup. In addition, he said, marine biologists that deal with red tide monitoring also came to harbor to assist, including from USC's marine biology department.

Fish, including anchovies, sardines and mackerel, were floating lifeless in Basins 1 and 2 of the north side of King Harbor Marina.

"There’s basically fish everywhere you go in the harbor," said the harbor's assistant manager, Jason McMullin, who added that there were reports that a red tide may have driven the fish into the harbor in massive numbers, where they died because of limited oxygen.

[Updated at 11:35 a.m.: Marine biologists from USC have been dispatched to King Harbor to test for elevated levels of dissolved oxygen, a key indicator of whether the cause of the fish die-off was a harmful algal bloom.

USC installed oxygen sensors in the harbor after a mass fish die-off in 2005, and since then researchers have been monitoring the harbor to better understand what happened, said biological sciences professor David Caron.

When there is a preponderance of algae in a single area, they can consume massive amounts of oxygen in the water and can deprive other sea creatures of the air they need to live. But algae can also produce toxins that can kill marine life.

“What we're trying to tease apart is whether it's a consequence of algal buildup, a fish buildup or something toxic in the water,” Caron said.

They plan to check the monitoring devices Tuesday and later use robotic vehicles to probe the harbor for other clues about the cause of the fish kill, Caron said.]


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-- Andrew Blankstein and Tony Barboza in Los Angeles and Nate Jackson in Redondo Beach

Photo: King Harbor from the air this morning. Photo credit: KTLA News.