Biological Criteria for Definition of Species and Distinct Intraspecific Populations of Anadromous Salmonids Under the U.S. Endangered Species Act of 1973
The validity of most recognized species of salmonids under the biological species concept is supported by evidence from diverse sources. However, the specific status of a number of recently diverged populations remains uncertain. In the United States, it is particularly important to consider the possibility of unrecognized reproductively isolated populations for protection under the U.S. Endangered Species Act of 1973 (ESA).Innate life history differences among species as well as numerous uncertainties within species preclude the use of a generalized model based on homing as the sole or primary means of defining discrete population segments of anadromous salmonid species. A process involving successive samplings, analyses, and syntheses of data from populations of a particular area is suggested. A major requirement of this process is reliable genetic data. The capability for the detection of allelic proteins by electrophoretic methods has provided a major tool for identifying and measuring genetic differences among populations and species. These data are necessary, but often insufficient for identifying most population segments and must be complemented by other biological and life history data as well as by historical and geological information. Provisional classifications of threatened or endangered populations on the basis of incomplete data may be necessary in many instances, but final classifications should depend on complete sets of data.Transplanted and hatchery populations complicate the identification and management of anadromous salmonid populations under the ESA. Some evidence is cited that indicates a potential or actual adverse genetic effect of hatchery or transplanted fish on some native populations, and current studies designed to measure such effects are mentioned. The technical and economical feasibility for measuring these effects suggest that such measurements should be a requisite for new or extended transplantation and hatchery operations.Further data are needed to determine whether or not threatened or endangered species and populations can be artificially perpetuated and still retain the capability to adapt to wild environments upon reintroduction to native habitats. This capability apparently exists in some domesticated strains of rainbow trout (Salmo gairdneri). However, large differences exist in the intrinsic levels of genetic variation between most domesticated populations of rainbow trout and many threatened or endangered natural populations of salmonids.Key words: criteria, intraspecific, anadromous salmonid populations, genetic data