Oil Rigs Jostle Sperm Whales in the Gulf of Mexico

COLLEGE STATION, Texas, May 24, 2001 (ENS) - A breeding population of about 530 endangered sperm whales in the Gulf of Mexico may be feeling the effects of an increase this year in deepwater oil and gas drilling.

Researchers have found that these whales frequent the deeper waters off the Mississippi Delta in the northeastern Gulf of Mexico.

whale

Sperm whale breathes after a dive in the Gulf of Mexico. (Photos courtesy Minerals Management Service U.S. Interior Dept.)
In a Texas Sea Grant funded project, Marine biologists Randall Davis and Bernd Würsig at Texas A&M University at Galveston plan to learn more about these sperm whales that live so close to the coast. They will use satellite tracking, direct observation, genetic analysis and photographic identification to trace the effect of oil drilling on the whales.

"Basically, we probably have a breeding population of endangered sperm whales right in the middle of one of the hottest areas for offshore oil development in the continental U.S," Davis said.

"The unique aspect of the Gulf is we have a continental shelf that is only about 25 miles wide off the Mississippi Delta, so we have this influx of freshwater nutrients into a deepwater environment very close to the coast," he said.

The Mississippi Delta region of the Gulf has water that is several thousand meters deep within 50 or 60 miles of the coast, Davis said, and sperm whales are typically found in these deeper waters along the continental shelf.

The sperm whales are sharing these waters now with increasing numbers of oil and gas rigs. These activities, and the boat traffic, chemicals, and noise they bring, may be a cause for concern Davis said.

The project is set up as a basic science study that looks at the natural history of sperm whales in the northern Gulf of Mexico. But Davis says the study's findings will likely be of interest to the Marine Mammal Commission, National Marine Fisheries Service as well as the Minerals Management Service, which oversees development of offshore oil and gas deposits.

The Endangered Species Act requires officials to monitor not only oil pollution but also noise pollution, which comes from boat traffic and seismic activity that is used to search for oil.

rig

Researchers approach a deepwater oil rig in the Gulf of Mexico.
The number of rigs drilling in deepwater in the Gulf of Mexico rose to a record high of 42 during the week of April 19, according to the Department of the Interior’s Minerals Management Service (MMS).

MMS Acting Director Tom Kitsos said, "This level of deepwater oil and gas activity illustrates the tremendous level of industry interest in the deepwater portion of the Gulf of Mexico. Last year began with 26 rigs working in deepwater, but that number continued to rise. By the end of the year, there were a record 40 rigs drilling in the deep waters of the Gulf. Now, just four months into 2001, a new record has been set."

MMS defines deepwater as 1,000 feet of water or greater. Of the 42 wells drilling in deepwater, 36 of them were in 1,500 feet of water or greater, and eight wells being drilled in water depths of 5,000 feet or greater." Production from these deepwater wells has now surpassed production in shallow water, despite the fact that only four percent of all producing fields in the Gulf of Mexico are in deepwater.

MMS must determine if offshore industry noise and marine seismic operations represent a threat to marine mammals and, if so, means to mitigate those effects. These determinations have been hindered by little data.

Sperm whales can dive for two hours to depths of 10,499 feet (3,200 meters) or more to feed on squid. Any release of hazardous chemicals by the drilling industry might affect the Gulf's sperm whales.

A study by MMS issued in March identifies eight hazardous substances used by the Gulf drilling industry that were stored in amounts exceeding reportable quantities - sodium hydroxide, potassium hydroxide, zinc bromide, hydrofluoric acid, diethylamine, toluene, xylene and naphthalene. A potential for environmental impact exists if either of two chemicals are spilled, zinc bromide and ammonium chloride, the MMS analysis showed.

Last summer, a group of scientists from the National Marine Fisheries Service, the Woods Hole Oceanographic Institute, University of Kansas, University of Durham and the University of St. Andrews in the UK, conducted a four week study of the Gulf sperm whales from a large research vessel equipped with sophisticated listening and tracking devices.

tagging

An Office of Naval Research acoustic tag is attached to a sperm whale from a 30 foot long pole. The tag has three suction cups and will remain attached for up to four hours. The released tag is located by radio signals and recovered so that movement data can be analyzed.
Six whales were tagged with satellite transmitters. About 50 photographs of sperm whale tails were shot for identification and 40 samples of whale tissue collected for DNA analyses using a biopsy dart fired at close range from a modified rifle.

The researchers found just one male during the four week study. "Virtually all sperm whales observed in the Gulf of Mexico are females, calves, and immature whale groups," they reported. But one large male, whose sex was confirmed by DNA analysis, was observed and photographed in the DeSoto Canyon region during the final days of the scientific cruise.

Currently, MMS and National Marine Fisheries Service scientists are working on plans for continuing sperm whale and acoustic studies this year.

The sperm whale is the largest of the world's toothed whales, measuring up to 59 feet (18 meters). Sperm whales live in deep waters, and are the most abundant large whale in the Gulf of Mexico, but other whales swim there too. Fin, blue, sei, fin, minke, Bryde's and humpback whales have been seen. Orcas, pygmy sperm whales and dwarf sperm whales, four species of beaked whales, pilot whales and 10 species of dolphins have been reported in the Gulf.