The U .S. government has designated three pods of genetically distinct killer whales, which travel between Georgia Strait and Puget Sound, as endangered.

Biologists estimate there are 80 to 90 Southern Resident killer whales left off the west coast. Their numbers have dwindled by 20 per cent since the late 1990s.

Labelling them as "endangered" means they are in danger of becoming extinct. It represents a higher level of protection than the "threatened" designation proposed by Washington last year.

The American decision follows a lengthy legal challenge by environmental groups from both sides of the border.

"We were overjoyed and at the same time incredibly relieved," says Gwen Barlee of the Western Canada Wilderness Committee.

"This is a population of orcas that is under an enormous amount of pressure, not only from loss of fish that they need to eat, but also pollution in the area."

Canada already offers similar protection to the whales. But the work necessary to help their population recover has been minimal according to the Sierra Legal Defense Fund.

The group's lawyer, Margot Venton, says she hopes classifying the orcas as endangered in the U.S. will have a ripple effect in Canada.

"We feel this will push Canada in the right direction to ensure proper resources are allocated under our Endangered Species Act which is much more discretionary than the American counterpart."

Biologists say its now up to wildlife officials from both sides of the border to develop an orca protection strategy together.