The ESA requires D to promulgate regulations listing those species of animals that are 'threatened' or 'endangered' under specified criteria, and to designate their 'critical habitat.' It requires each federal agency to 'ensure that any action authorized, funded, or carried out by such agency . . . is not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modification of habitat of such species which is determined by the Secretary . . . to be critical.' If D concludes that the proposed action will 'jeopardize the continued existence of any [listed] species or result in the destruction or adverse modification of [critical habitat],' D must outline any 'reasonable and prudent alternatives' that it believes will avoid that consequence, § 1536(b)(3)(A). If the agency action will not result in jeopardy or adverse habitat modification, or if it offers reasonable and prudent alternatives to avoid that consequence, D must provide a written statement (known as the 'Incidental Take Statement') specifying the 'impact of such incidental taking on the species,' any 'reasonable and prudent measures that the [Service] considers necessary or appropriate to minimize such impact,' and setting forth 'the terms and conditions . . . that must be complied with by the Federal agency . . . to implement [those measures].' D issued a Biological Opinion which concluded that the ''long-term operation of the Klamath Project was likely to jeopardize the continued existence of the Lost River and shortnose suckers.'' It identified 'reasonable and prudent alternatives' to avoid jeopardy, which included the maintenance of minimum water levels on Clear Lake and Gerber reservoirs. D notified everyone that it intended to operate the project in compliance with the Biological Opinion. P filed the present action in that 'there is no scientifically or commercially available evidence indicating that the populations of endangered suckers in Clear Lake and Gerber reservoirs have declined, are declining or will decline as a result' of the present manner of operation of the Klamath Project. Ps asserts that their use of the reservoirs and related waterways for 'recreational, aesthetic and commercial purposes, as well as for their primary sources of irrigation water' will be 'irreparably damaged.' The District Court dismissed the complaint for lack of jurisdiction because Ps 'recreational, aesthetic, and commercial interests . . . do not fall within the zone of interests sought to be protected by ESA.' The Court of Appeals for the Ninth Circuit affirmed. The Supreme Court granted certiorari.