... 1996¹

If you visit the Fish & Wildlife Service's page on Endangered Species Related Laws, Regulations, Policies, & Notices (http://endangered.fws.gov), you won't find any mention of the hybrid policy. That's because the policy was proposed, but never adopted. You can find a mention of an early version of it in [7].

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... concept²

``A species is a group of actually or potentially interbreeding natural populations that are reproductively isoated from other such groups'' [6].

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... units''³

More on that in a moment

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... depends.''⁴

Sounds a lot like arguments about species definitions, doesn't it?

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... fish⁵

Waples is an employee of the National Marine Fisheries Service, and the policy Pennock and Dimmick criticize arose, in part, from Waples' attempt to arrive at a method for identifying ``distinct population segments'' of Pacific salmon. That policy is codified in Federal regulations for conservation of salmonid species native to the Pacific (56 CFR 58612-58618; November 20, 1991). Current policy for recognizing distinct population segments of vertebrates (61 CFR 4722-4725; February 7, 1996; http://endangered.fws.gov/policy/pol005.html) is less restrictive. Its definition of discreteness requires either that ``It is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors'' or that ``It is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D) of the Act,'' i.e., existing regulatory mechanisms are inadequate for protection.

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