Over the past 12 weeks, hundreds of leopard sharks have washed up dead on the shores of San Francisco.
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The deaths are surprising scientists, but they’ve formulated a complex working theory as to why.
According to SFGate.com, the source of the sharks’ infections “comes down to the city’s use of tide gates in residential areas near inland waterways,” says Sean Van Sommeran, executive director and founder of the Pelagic Shark Research Foundation.
To keep from flooding during the rainy season, Redwood City closes its tide gates during low tide.
“That way, when there are heavy rains, the extra precipitation doesn’t combine with high tides to flood homes along the water. The problem is that leopard sharks come into the shallow waterways to mate and pup during the spring and summer, so they often get trapped when the tide gates close.”
And with the intense rain, “extra crud” goes into the water; hence, the sharks get sick.
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Despite this possible break in research, scientists say more testing is needed before they can definitively say what is causing the mass die-offs.