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Great white shark sighting reported off Malibu--part II

September 25, 2008 |  8:46 am

To amend yesterday’s “Great white shark sighting reported off Malibu” posting, and my statement that adult white sharks typically leave Southland coastal waters once they begin to prey on seals and sea lions instead of fish, I'm adding comments e-mailed by Ralph S. Collier of the Shark Research Committee:

In regards to the prior migratory movements of adult white sharks off the Southern California coastline, in the past it was necessary for the sharks, once they had pupped, to travel to Central and Northern California because the majority of the pinniped rookeries and haul-out sites were in those locations.

Today is a different story. At last count, pinnipeds number more than 300,000 in the state and large numbers have taken up residency in Southern California. This precludes the sharks from migrating North with such a plentiful supply of energy (pinnipeds) along our coastal shoreline. However, this could have a negative effect on the survival of the newborn sharks. In time we will be able to determine the real cause and effects of the 1972 Marine Mammal Protection Act.

The first part makes sense to me. Scientists may claim there are no studies to support this theory, but anyone who spends time on the ocean can attest to the phenomenal population explosion among California sea lions, and their proliferation in Southern California.

They’re atop every buoy and in every harbor, and around just about every fishing boat, stealing fish from anglers’ hooks. In fact, commercial and recreational fishermen now largely despise sea lions and wish their numbers could be culled.

Still, truly large adult white sharks prefer elephant seals to sea lions, because there’s more sustenance in the larger pinnipeds, and they maintain a high site fidelity to seal rookeries.

But it certainly would seem there is less urgency among 10- to 12-foot white sharks to begin heading north. Similarly, if adult white sharks pup in Southland waters -- and there is no proof they do -- they might be less inclined to rush off with all those sea lions in their midst.

This is not to suggest the danger factor for surfers and swimmers has increased. Shark attacks on humans have always been and will remain extremely rare. But surfing or swimming alone over reasonably deep water is never a good idea.

-- Pete Thomas

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