A national environmental group is asking the Obama administration to list a large ocean mammal that lives in Hawaiian waters as an endangered species because only 120 of the animals remain.

Over the last 20 years, the Hawaiian false killer whale population has suffered a significant decline and continues to face several threats to its survival, according to a petition submitted yesterday by the Natural Resources Defense Council.

The council seeks to designate a critical habitat to ensure the animal's recovery.

“;Given the extremely small size of this population, the loss of even a few mature adults could have serious and long-term reproductive consequences,”; said Sylvia Fallon, a wildlife biologist with the council.

The national, nonprofit council was involved in legal action to protect the Arctic National Wildlife Refuge from oil drilling under the Bush administration, to stop worldwide deployment of a Navy sonar system that may be harmful to whales, and to protect the polar bear under the Endangered Species Act.

The Hawaiian whales are members of the dolphin family and can grow to 20 feet and weigh 1,500 pounds.

The council said the mammal is being threatened by toxic chemicals, reduced food sources and interactions with fishing vessels.

Both long-line and unregulated near-shore fishing affect the population, and fisheries may be decreasing the whales' primary food source — large deepwater fish, including mahi mahi and yellowfin tuna, according to the council.

While deepwater hunters, the Hawaiian false killer whale population is the only group of the species known to make its home near land, rarely straying farther than 50 miles. That shows the importance of Hawaiian waters as an oasis for marine mammals, the council said.