## Facts

- The U.S. Fish and Wildlife Service (FWS) and National Marine Fisheries Service (NMFS) adopted a 1996 joint “distinct population segment” (DPS) policy to interpret the Endangered Species Act’s (ESA) undefined term “distinct population segment.”
- The DPS policy uses a three-step framework: (1) discreteness, (2) significance, and (3) conservation status; discreteness may be shown by marked separation or by international boundaries tied to meaningful regulatory differences.
- In 2000, the Services listed the Gulf of Maine DPS of Atlantic salmon as endangered under the ESA, citing threats such as low natural survival, poaching, and impacts from aquaculture and hatcheries.
- The State of Maine and several Maine business organizations sued federal officials under the Administrative Procedure Act (APA), challenging both the DPS policy and its application to the Gulf of Maine salmon listing.
- The parties filed cross-motions for summary judgment based on the administrative record.

## Issues

1. Whether the Services’ 1996 DPS policy exceeded statutory authority or conflicted with congressional intent under the ESA, including by permitting consideration of political boundaries in defining discreteness.
2. Whether listing the Gulf of Maine Atlantic salmon as an endangered DPS was arbitrary or capricious under the APA, including whether the Services used the best available scientific data and reasonably assessed existing state regulatory measures.

## Decision

- The court granted summary judgment for the federal defendants and denied plaintiffs’ motions.
- The court upheld the 1996 DPS policy as a permissible interpretation of the ESA.
- The court upheld the endangered listing of the Gulf of Maine Atlantic salmon DPS as supported by the administrative record and not arbitrary or capricious.

## Legal Principles

- When a statute leaves a material term undefined, an agency may fill the gap with a reasonable interpretation consistent with the statutory scheme, and reviewing courts defer to that interpretation.
- Under the ESA, a DPS determination may be structured through agency criteria (discreteness, significance, and status) so long as the criteria reasonably implement the statute’s conservation objectives.
- Consideration of international political boundaries as evidence of discreteness is permissible when tied to meaningful differences in habitat management or regulatory mechanisms.
- Under APA arbitrary-and-capricious review, the court examines whether the agency considered relevant factors and explained a rational connection between the record and the decision, not whether the court would reach the same scientific judgment.
- The ESA requires use of the “best scientific and commercial data available,” allowing agencies to rely on qualified expert judgment despite scientific disagreement.
- In listing decisions, agencies must consider “existing regulatory mechanisms” and may reasonably conclude that state programs are insufficient to address identified threats.

## Conclusion

The court held that the Services acted within their statutory authority in adopting the DPS policy and reasonably applied it to list the Gulf of Maine Atlantic salmon as endangered, based on record-supported scientific findings and an adequate evaluation of regulatory protections under the ESA.


Maine v. Norton, 257 F. Supp. 2d 357 (D. Me. 2003)