Dozens of leopard sharks have washed up on shores near Redwood City, California over the past month, but city officials and one shark expert are at odds over the probable cause.
Not Enough Oxygen?
The Daily Post reports that Sean Van Sommeran, executive director with the Pelagic Shark Research Foundation in Santa Cruz, suspects the deaths in Redwood Shores were caused by low oxygen levels in ponds as a result of closed tidal gates.
But according to the Daily Post, Redwood City Public Works Director Evan Boyd said preliminary tests on oxygen levels showed that wasn’t the case. He also disputed the tidal gates theory, saying the city found dead sharks both on days when the gates were open and closed.
How Did So Many Leopard Sharks Die?
Van Sommeran is convinced that canals that regulate tide flow may be preventing the sharks, which usually grow about five feet long, from escaping some kind of toxic discharge or other manmade pollution source.
“We’re mapping and photographing and making contact with the management for the nearby facilities that control the flow of water through those manmade canals,” he said.
Leopard sharks are a non-aggressive species that tend to ignore humans and can live up to 40 years. Van Sommeran said they are very common up and down the California coast.
“They’re a very important feature of the Monterey and San Francisco Bay areas, kind of a signature species of California as well,” he said.
Shark die-offs are not unusual, although Van Sommeran said they are becoming more common.
So far, this die-off appears less severe than more widespread incidents in 2006 and 2007, although it is possible that other creatures succumbing to the unidentified toxin or pollutant could be floundering further from land.
Leopard Sharks Acting Oddly In San Francisco Bay
Meanwhile, the Richardson Bay Audubon Center & Sanctuary has noticed a few leopard sharks in the San Francisco Bay, just a few miles from Redwood City, that seem to be either sick or acting oddly lately. Could this be connected to those recent deaths?
You can see a video of these sharks by clicking here.
Photo Credit: bikehikedive via Creative Commons
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