In April 2009, the US established a United States National System of Marine Protected Areas, which strengthens the protection of US ocean, coastal and Great Lakes resources. These large-scale MPAs should balance "the interests of conservationists, fishers, and the public." As of 2009, 225 MPAs participated in the national system. Sites work together toward common national and regional conservation goals and priorities. NOAA's national marine protected areas center maintains a comprehensive inventory of all 1,600+ MPAs within the US exclusive economic zone. Most US MPAs.allow some type of extractive use. Fewer than 1% of U.S. waters prohibit all extractive activities.