Mass die-off in the Pacific as hundreds of sharks wash up on the shores of San Francisco

Monday, May 15, 2017
By Paul Martin

by: D. Samuelson
Monday, May 15, 2017 reminds us that sharks are both scavengers and super -predators, who greatly assist in keeping the ocean’s ecosystem balanced. Sharks eat fish that are the “weakest, sick or dead,” and also “maintain prey species diversity” by keeping other predator species in check. A decline in shark populations not only threatens fishery operations, but can also indicate deeper problems within our ecosystem. This may be the case in the waters of the Pacific Ocean off the coast of San Francisco, where for more than seven weeks, hundreds of Leopard sharks have been found dying, or dead, as reported by the San Francisco Gate.

This isn’t the first time the Leopard shark has had a die-off. states that the Leopard shark had a population decrease in 2016, as well as in 2011, when a thousand dead leopard sharks perished and washed up on shore with scientists estimating those numbers might be much higher. This year’s die-off could be “in the thousands,” as well. According to Sean Van Sommeran, founder and executive director of the Pelagic Shark Research Foundation, an education and shark research consortium based in Santa Cruz, California, this event could be “just the tip of the iceberg.”

The epicenter where many of the dead sharks have been found is Redwood City, California. This has led Van Sommeran to surmise that the cause of the deaths can be attributed to the closing of the Redwood City tide gates during low tide, which is done to prevent flooding during the rainy season. When the tide is low, however, the leopard sharks are making their way into the shallower waters to mate. When those flood gates close, the sharks get trapped and exposed to storm water runoff, which contains what Van Sommeran calls “extra crud going into the watershed.” The water inside the gates becomes stagnant and creates a toxic environment in which the shark cannot survive. When the tide gates are reopened, those rotting carcasses of dead sharks are released into the waters and then contaminate others. Here’s a brief synopsis of the current explanation of this year’s die-off, which is still in progress:

The Rest…HERE

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