WASHINGTON (Reuters) - The U.S. Border Patrol, unveiling its first new strategy in eight years on Tuesday, said it aims to become more nimble as illegal immigration plummets.

The new plan calls for increased intelligence gathering, greater cooperation with other law enforcement agencies and quicker deployment to combat the biggest risks, said Border Patrol Chief Michael Fisher.

The change means a shift away from the strategy of deploying a growing army of agents at trouble spots. The number of agents has more than doubled to 21,000 since the last plan in 2004, along with a heavy investment in boats, aircraft, cameras and other equipment.

"The principal theme of the 2012 Strategic Plan is to use information, integration and rapid response to meet all threats," Fisher said in prepared remarks before the House of Representatives' subcommittee on Border and Maritime Security.

The previous plan also focused on organizing the Border Patrol after the September 11, 2001, attacks and melding it into the new Department of Homeland Security, he said.

The more nuanced approach reflects sharply different conditions on the U.S-Mexico border as immigration has slowed.

Arrests on the southwest border last year were down more than 80 percent from the peak year of 2000. Violent crime in the region has fallen by an average of 40 percent over the last 20 years, Fisher said.

The Pew Hispanic Center reported last month that the largest wave of immigration from a single country to the United States had come to a halt and may have reversed.

Fisher said the Border Patrol's main goals included "preventing terrorists and terrorist weapons" from entering the country and to disrupt cross-border criminal gangs.

Republican Representative Candice Miller of Michigan, the subcommittee's chairman, praised the Border Patrol for its "extraordinarily professional job" in protecting the border.

But she also questioned how the new strategy could be shown to be working since it relied on assessing risks rather than such numbers as miles of border controlled or number of arrests.

"The border may be more secure, but by what? How do you measure it?" she said.

(Reporting By Ian Simpson; Editing by Cynthia Osterman)