Watching whales and whale sharks

A government ship sets off Thursday to tag and track whales, dolphins and 19 other species of marine mammals in Gulf waters. The aim is to see whether the BP spill is impacting individuals and larger populations.

Scientists hope to tag 21 sperm whales, for example, "to see if the spill will affect the size of their 'home range' and their movements within feeding areas," the National Oceanic and Atmospheric Administration says in a statement.

Buoys with listening devices will also be deployed for up to four months to record "the moans, clicks and whistles" of whales and dolphins. "These records will allow scientists to track changes in the occurrence of marine mammals as the amount of oil exposure changes throughout the summer and fall," NOAA said.

"By recording the sounds from all the marine mammals that live in the Gulf of Mexico, we can get a more complete picture of the health of this ecosystem," said researcher John Hildebrand. "By beginning our study soon after the spill began, we may see trends in the presence of animals in the affected area."

The study comes as a separate researcher reported spotting three whale sharks, the world's largest fish, swimming in oily waters.

"Our worst fears are realized. They are not avoiding the spill area," Eric Hoffmayer, a University of Southern Mississippi scientist, was quoted in the Mobile Press-Register as saying. "Those animals are going to succumb. Taking mouthfuls of oil is not good. It is not the toxicity that will kill them. It's that oil is going to be sticking to their gills and everything else."

Last week, Hoffmayer was the first to spot a group of 100 whale sharks -- one of the largest congregations ever seen in the Gulf. The species migrate north in late spring from waters near the Yucatan to feed off the mouth of the Mississippi River.

While it's not known how many whale sharks exist, they are on the World Conservation Union's "red list" of threatened species.