ZANZIBAR, Tanzania - Scientists worked on Saturday to try to determine why hundreds of dolphins became stranded in shallow waters and later washed up dead along the shore of a popular tourist destination on Zanzibar's northern coast.

At least 400 dead dolphins were found on Zanzibar's northern coastline early Friday, April 28, 2006, alarming villagers, fishermen and tour operators, residents said. It was not immediately clear what killed the dolphins, whose carcasses were found along a 4-kilometer (2.5-mile) stretch of Nungwi, a popular tourist destination in this semiautonomous Indian Ocean archipelago, said Narriman Jidawi, a marine biologist at the Institute of Marine Science in Zanzibar. (AP Photo/Ali Sultan)

Villagers and fishermen buried the remains of about 400 bottleneck dolphins - which live in deep offshore waters - whose carcasses washed up on Friday along a 4km stretch between Kendwa and Nungwi.

Scientists suspect the animals were disturbed and stressed by some unknown factor, or were poisoned before they died, said Narriman Jiddawi, a marine biologist at the Institute of Marine Science of the University of Dar es Salaam.

A preliminary examination of their stomach contents failed to show the presence of squid beaks and otoliths - the ear stones that are found directly behind the brain of bony fishes that are eaten by dolphins, Jiddawi said.

This indicates that the dolphins had either not eaten for a long time or had vomited very severely, she said.

Their general condition, however, appears to show that they had eaten recently since their ribs were not clearly visible under the skin.

Experts were preparing to further examine the dolphins' stomachs for traces of residue poison, including from the toxic "red tides" of algae.

Experts also planned to examine the dolphins' heads to assess whether they had been affected by military sonar.

In the United States, experts were investigating the possibility that sonar from US submarines could have been responsible for a similar incident in Marathon, Florida, where 68 deep-water dolphins stranded themselves in March 2005.

A US Navy task force patrols the coast of East Africa as part of counterterrorism operations. A navy official was not immediately available for comment, but the service rarely comments on the location of submarines at sea.

Zazinbar's resorts attract many visitors who come to watch and swim with wild dolphins.

The Indo-Pacific bottlenose, humpback and spinner porpoises, commonly known as dolphins, are the most common species in Zanzibar's coastal waters, with bottlenose and humpback dolphins often found in mixed-species groups.

The most conclusive link between the use of military sonar and injury to marine mammals was observed from the stranding of beached whales in 2000 in the Bahamas. The US navy later acknowledged that sonar likely contributed to the stranding of the extremely shy species.

"These animals must have been disoriented and ended up in shallow waters, where they died," fisherman Abdallah Haji, 43, said as he helped bury the dolphins near the bloodied beach.

Residents had cut open their bellies to take the animals' livers, which they use to make waterproofing material for boats.

"We have never seen this type of dolphins in our area," said the man, who has fished in Zanzibar waters for more than two decades.

© Copyright 2006 Associated Press

###