Heavy rains could be to blame for shark die-off

May 20, 2011 12:06:19 AM PDT
An alarming number of dead sharks are turning up around San Francisco Bay. The latest wave is in Marin County's Richardson Bay. And with so many washing ashore some people have noticed the sharks' strange behavior recently.

There are theories, but no one knows for sure why the sharks are dying. Lots of leopard sharks have been found washed ashore in Tiburon.

Lara Martin has found yet another dead leopard shark. It's among a couple dozen that have turned up off the shores of Richardson Bay in the past few weeks. Martin is a researcher at the Richardson Bay Audubon Center, which is trying to get to the bottom of what's killing the sharks.

"Whenever you have too many of a species dying off, it just indicates that something is out of balance," said Martin. "Oh, it's kind of wrenching. I mean, I really like sharks, so it's just kind of sad."

Leopard sharks enter Richardson Bay this time of year to spawn, but rarely do they turn up dead along the shore. Karen Zaluski of Tiburon discovered two dead sharks two weeks ago, and shortly after that, saw another one acting strangely.

"It kind of kept getting stuck in the mud. And this guy -- we went to go check it out -- and this guy came down to try and help it out, we thought it was just stuck in the mud but it kept swimming back in, like its radar was off or something," said Zaluski.

More than 100 sharks have also been turning up dead, farther south in San Mateo County. The Department of Fish and Game is conducting necropsies, but so far the prevailing theory is that heavy winter rains have diluted the saltwater in the bay -- throwing the sharks' body chemistry out of balance.

"They can exist in a midrange saline environment. They don't need full ocean conditions, but anything below 15 to 18 parts per thousand, they would probably have a difficult time," said Martin.

Tiburon residents ABC7 talked to say they hope researchers figure it out soon. While they're worried about the sharks, they're also concerned about the overall quality of the water.

"Anything to do with the nay or the water concerns me because this is what we have and we have to protect it," said Tiburon resident Chris McKay.

The Richardson Bay Audubon Center would like the public's help. They're asking people to report any leopard shark in distress.


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