Property-rights advocates and California farmers have filed a petition urging the government to delist Pacific Northwest orcas from the Endangered Species Act, arguing that group of whales is not a sub-species.

Sacramento, Calif.-based Pacific Legal Foundation filed its petition Thursday with the U.S. Department of Commerce and the National Oceanic & Atmospheric Administration. A previous petition by this group failed in 2006.

The orcas in question live year round in the Puget Sound and nearby Canadian waters. They were listed as endangered in 2005.

The petition alleges that the orcas' endangered listing has affected water supplies to California farmers due to restrictions placed to protect salmon that the orcas eat.

Conservationist group Earthjustice spokeswoman Kristen Boyles says biologists have determined these orcas have distinct dialects, pod structures and diets.