November 25, 2013 at 12:52 am #1244MikeKeymaster
South Bay fish deaths puzzle experts
More answers expected today or next week
By Julia Scott, STAFF WRITER
REDWOOD CITY — Dennis Rogers knew something was amiss last Tuesday
morning when the Marine Science Institute’s research vessel left port
and was surrounded by dead fish.
“We noticed them as we were motoring out. They were floating all
No matter where you stopped you’d see three or four of them,” said
Rogers, the Institute’s Land Program coordinator.
Over the next few days, officials would find more than
1,000 dead fish, primarily striped bass but also some sturgeon,
floating on the water’s surface between the San Mateo-Hayward and
Dumbarton Bridges in the South Bay.
Samples from the fish were sent to a lab run by the California
Department of Fish and Game to determine the cause of the die-off.
The results were expected today or early next week.
“At this point, we don’t know what it is other than all the fish are
dead,” said Fish and Game spokesman Troy Swauger. “But it is not a
human-caused situation. It does not appear to be an oil spill or a
toxic spill that would have caused this.”
Swauger said he couldn’t recall the last time a die-off of this
magnitude occurred in the Bay. He said 30 leopard sharks died in June
and begun washing up on the shores of Coyote Point, Berkeley, San
Francisco’s Crissy Field, and as far away as San Rafael. Their cause
of death was also unclear, but was not thought to be related to the
fish, he said.
“It’s not unusual for fish to die of natural causes,” said Swauger.
Algae blooms caused by nutrient-rich
waters, low tides and high temperatures can sometimes deprive fish of
the oxygen they need to survive, creating anoxic “dead zones”
throughout the Bay.
“However, this is a larger area — so that’s why we’re doing the
investigation,” he said.
Becky Ota, a Fish and Game marine region biologist in Belmont,
confirmed that there had been reports of a plankton bloom in South
Bay waters in May.
Rainer Hoenicke, an environmental scientist with the San Francisco
Estuary Institute, said this was the first major fish die-off in the
Bay in the past 10 years. Improved wastewater treatment procedures
had improved the overall health of the Bay, he said, and he hadn’t
heard of any chemical spills recently.
At the same time, Hoenicke thought scientists shouldn’t rule out the
possibility that human actions may have indirectly affected the
conditions of the fish’s habitat.
“For me, there has to be some contributing factor that fish get so
stressed and just kick the bucket,” he said.
Staff writer Julia Scott covers the coast and the environment.
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