The Endangered Species Act (ESA) protects species that are at risk of extinction, and also provides for the conservation of the ecosystems on which they depend. The U.S. Fish and Wildlife Service and NOAA Fisheries share responsibility for implementing the ESA. Generally, U.S. FWS manages land and freshwater species, while NOAA Fisheries is responsible for marine and anadromous species.  

A species is considered endangered if it is in danger of extinction throughout all or a significant portion of its range. A species is considered threatened if it is likely to become endangered in the future. The listing of a species as endangered makes it illegal to "take" that species (i.e., harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, collect, or attempt to do these things). Similar prohibitions may be extended to threatened species.

Under the ESA, NOAA Fisheries works to conserve and recover marine resources by:

• Listing species under the ESA and designating critical habitat.
• Developing and implementing recovery plans for listed species.
• Developing cooperative agreements with and providing grants to states for species conservation.
• Consulting on any federal actions that may affect a listed species, to minimize the effects of the action.
• Partnering with other nations to ensure that international trade does not threaten species.
• Investigating violations of the ESA.
• Cooperating with non-federal partners to develop conservation plans for the long-term conservation of species.
• Authorizing research to learn more about protected species.