A prehistoric fish may turn out to be a serious obstacle to the controversial proposed Northern Gateway pipeline.

The $5-billion Enbridge Inc. project to pipe bitumen from Alberta's oil sands operations west to a planned export terminal at Kitimat, on the northern B.C. coast, faces stiff resistance from environmentalists and First Nations.

Now The Canadian Press reports that absence of a legally required federal plan to protect the endangered Nechako white sturgeon will be used as a lever against the project.

The proposed route for the pipeline crosses the Stewart and Endako rivers, home to about 335 of the giant fish, which are listed as endangered under the Species At Risk Act (SARA), CP reported.

The law obliges Ottawa to come up with a recovery plan for listed species but the plan for the sturgeon, which was supposed to be implemented in 2009, has been gathering dust in draft form for seven years.

"That [plan] creates an obligation on the government to ensure that the critical habitat of the white sturgeon is legally protected," Susan Pinkus, a biologist for EcoJustice, told CP.

Sturgeon, which can live to be more than 100 years old, have existed largely unchanged since the time of the dinosaur. They can grow up to six metres in length and weigh up to 500 kilograms.

Other sturgeon are found in the Fraser River in southern B.C., where they're sometimes caught by fishermen but always released after being tagged and photographed. Two 500-kg. sturgeon were caught this year.

A coalition of conservation groups that includes EcoJustice plans to sue the government in Federal Court to get it to enforce its own legislation on the proposed pipeline route, CP said.

"This is a population that [the Department of Fisheries and Oceans] has assessed as being able to tolerate no additional harm, for obvious reasons," said Pinkus. "These guys are just barely hanging on."

"The lawsuit challenges the federal government's multi-year delays in producing recovery strategies for four species that would be affected by the proposed Enbridge Northern Gateway project — the Pacific Humpback Whale, Nechako White Sturgeon, Marbled Murrelet and Southern Mountain Caribou," the environmental coalition said in a news release Wednesday.

"The habitat for all four species, which lies along the proposed pipeline and shipping route, would be impacted by the construction and operation of the Northern Gateway pipeline.

"The recovery strategy for each of these species is at least three years overdue."

Documents obtained by CP under access-to-information legislation make numerous references to the sturgeon and humpback whales, as do documents filed with the National Energy Board's joint review panel now holding hearings into the Northern Gateway project.

"Under SARA, all harm, harassment or killing of individuals from a species listed as endangered or threatened is prohibited," said a Fisheries and Oceans memorandum on the project, according to CP.

The Fisheries document noted several species of concern along the proposed pipeline route, CP said, including the two species of rockfish, northern abalone and the eulachon, a smelt-like fish long fished by First Nations.

A Fisheries document submitted to the Northern Gateway review panel proposed an above-ground siting of the pipeline along the Endako River, which the department said would have negligible impact on the sturgeon, CP reported.

"However, there is some risk that a trenchless crossing may not be feasible because of the site conditions," the Fisheries documents say, adding that the contingency plan has an elevated risk of adverse impacts.

"It will be important for the proponent to ensure mitigation measures are sufficient and are implemented to avoid the risk of impacts to sturgeon."

The department concluded the risk to fish and their habitat could be managed through mitigation and compensation, CP said.