Sunday, May 27, 2007

Tagged Great White Shark, shows up in warm waters

A tagged great white shark traveled 2,200 miles at depths of up to 1,000 feet in a three month trip from near the Monterey Bay to the southern tip of the Baja Peninsula, according to data released Tuesday from the Monterey Bay Aquarium and Stanford University.

The tracking information offers a rare window into where young great white sharks go in Southern California. It paints a picture of the shark's daily life and, in this case, it shows a young shark's clear preference for warm water: The white shark moved steadily from colder Northern California waters to the warm waters of the Sea of Cortez, said John O'Sullivan, the aquarium's curator of field operations and husbandry and the white shark program's manager.

"It shows you the extensive areas that young white sharks utilize for their life," O'Sullivan said.
The data also highlights challenges facing both the United States and Mexico as the two governments work toward conservation, he added. "If they just went to the Guadalupe Islands or the Farallones, management would be easy."

The data was captured in an electronic tag about the size of a microphone that popped free on schedule from the shark about 25 miles from Cabo San Lucas on the Baja Peninsula on April 15 and was recovered eight days later in 4-foot seas.

The shark, caught last August off Los Angeles and released at the southern end of Monterey Bay in January, apparently spent days near the surface, with occasional dives to 600 feet and beyond,
according to Kevin Weng, a shark researcher at Stanford's Hopkins Marine Station.

Nights were spent oscillating in deeper waters about 250 feet. The deepest dives came at dawn and dusk. Researchers said Tuesday they can only assume the dives were for feeding, while the time at the surface was simply spent in transit to new feeding grounds.

The most tantalizing tidbit, researchers agreed, was where the tag released: At an important seamount at the entrance of the Sea of Cortez, the Cabrillo Seamount, known in Mexico as Bajo Cabrilla.

Seamounts -- underwater mountains that don't break the surface as islands do -- are important habitat and foraging grounds for many open ocean animals.

"The tag popped up at the entrance to the Sea of Cortez, at the southern end of the known range for juvenile white sharks," Salvador Jorgensen, a postdoctoral researcher with the aquarium and the Hopkins Marine Station, said in a statement. "Juvenile and adult white sharks have been captured inside the Sea of Cortez but we don't know whether they are born there or migrate in and out. So it's very interesting to see this juvenile show up right at the entrance."

Contact Douglas Fischer at or (510) 208-6425.


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