"La Nina" effect may be behind shark attacks

By Mariano Castillo

ZIHUATANEJO, Mexico (Reuters) - Cooler than normal sea-surface temperatures due to the La Nina phenomenon may be partly responsible for a spate of fatal shark attacks off Mexico's Pacific coast, a U.S. shark expert said on Friday.

At least two people -- a surfer and a U.S. tourist -- have been killed by sharks in the last few weeks around the coastal town of Zihuatanejo in the state of Guerrero.

La Nina, which usually results in cooler than normal water in the Pacific, has moved the boundary between cold and warm water closer to the shore, and along with it, fish and their shark predators, George Burgess, director of the Florida Program for Shark Research told Reuters.

The last time Mexico's Pacific coast suffered a series of fatal shark attacks was in 1972-1973, when four people were killed.

"One of the factors we're investigating is if there are special oceanographic conditions that might have contributed to the attacks," said Burgess, who was invited by Guerrero state officials to investigate.

Burgess and a Mexican researcher have pored over medical and police records and interviewed eyewitnesses, but said more research was needed before a definite cause could be found.

Burgess suspects more than one killer shark was responsible for the attacks and they were probably bull sharks.

"Bull sharks are probably the species that we as humans need to fear the most because they live close to shore and inhabit the waters that we as humans most often visit," he said.