The White House announced Monday it will require environmental reviews for all new deepwater oil drilling.

That brings to an end, at least for now, the kind of exemptions that allowed BP to drill with little scrutiny the well in the Gulf of Mexico that later exploded.

A shrimp fisherman shows off some of his catch on Monday, the first day of the shrimp season off Louisiana since the Deepwater Horizon oil spill. (Gerald Herbert/Associated Press)

A report by the White House Council on Environmental Quality found BP got environmental exemptions based on decades-old data.

"Our decision-making must be fully informed by an understanding of the potential environmental consequences of federal actions permitting offshore oil and gas development," Interior Secretary Ken Salazar said in a statement.

For now, new deepwater drilling in the Gulf is under a moratorium.

Once that's lifted, however, the Interior Department's new policy will likely make it much more time-consuming for oil companies to move ahead with new deepwater projects, since environmental assessments will be required along the way.

The move came the same day that shrimp fishermen returned to Louisiana waters for the first commercial season since the disaster.

The reopening came amid uncertainty about what crude may still be in the water and what price the fishermen will get for the catch if consumers worry about its possible lingering effects.

The spill has hurt the fishing industry in a state that ranks first in the U.S. in producing shrimp, blue crab, crawfish and oysters. It is worth $318 million US a year to Louisiana.

No date for bottom kill

Also Monday, the Obama administration's point man on the spill said no date has been set for finishing the final plug on the blown-out well.

Retired Coast Guard admiral Thad Allen said the order to proceed with using the relief well won't be issued until officials are convinced it's safe to go ahead.

Once the order is given for the so-called bottom kill operation, he told reporters, it will be roughly seven days before the well is dead.

The procedure involves pumping mud and cement into the well below the seafloor to permanently plug it.

Allen said scientists and engineers from BP and the federal government are looking at two options to relieve pressure inside the well so that the pumping of the sealing materials for the bottom kill can go ahead.

The first option would replace the existing equipment, choking off the flow of oil, while the other option would build a pressure-relief system into the existing equipment.

A cap has kept oil from flowing into the sea for weeks, but the government says a permanent plug is still needed.

With files from The Associated Press