Questions and Answers for 12-Month Not Warranted Findings on the Petitions to List Oregon Coast and Southern Oregon and Northern California Coastal spring-run Chinook Salmon as Threatened or Endangered

In 1998, we identified the Oregon Coast Chinook salmon Evolutionarily Significant Unit (ESU) as including both spring-run and fall-run Chinook salmon and determined that the ESU did not warrant listing as threatened or endangered under the Endangered Species Act (ESA).  In 1999, we identified the Southern Oregon and Northern California Coastal Chinook salmon ESU as including both spring-run and fall-run Chinook salmon and determined that the ESU did not warrant listing as threatened or endangered under the ESA. On September 24, 2019, we received a petition from the Native Fish Society, Center for Biological Diversity, and Umpqua Watersheds to delineate a new ESU for Oregon Coast spring-run Chinook salmon and list the ESU as threatened or endangered under the ESA.  On May 4, 2020, we received a petition from Richard K. Nawa to delineate a new ESU for Southern Oregon and Northern California Coastal spring-run Chinook salmon and list the ESU as threatened or endangered under the ESA.

We now announce our final determination on the petitions.  We find that Oregon Coast and Southern Oregon and Northern California Coastal spring-run Chinook Salmon populations do not constitute ESUs.  Accordingly, Oregon Coast and Southern Oregon and Northern California Coastal spring-run Chinook Salmon populations do not meet the statutory definition of a species, and thus, do not warrant listing under the ESA.

What is the difference between a species and an ESU?

The ESA defines “species” to include any “distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.” In 1991, we issued the Policy on Applying the Definition of Species Under the Endangered Species Act to Pacific Salmon (ESU Policy; 56 FR 58612; November 20, 1991), which explains that a Pacific salmon population unit will be considered a DPS, and hence a ‘‘species’’ under the ESA, if it represents an “evolutionarily significant unit” of the biological species.

What criteria do we use to identify ESUs?

The two criteria for delineating an ESU are: 1) It is substantially reproductively isolated from other conspecific population units, and 2) it represents an important component in the evolutionary legacy of the species.

What factors are used to determine the reproductive isolation of a population?

Reproductive isolation refers to restricted interbreeding among populations.  Such isolation does not have to be absolute, but it must be strong enough to permit evolutionarily important differences to accrue in different population units.  Information that can be useful in determining the degree of reproductive isolation includes documentation of fish straying from one population to another, recolonization rates of other populations, the efficacy of natural barriers to migration, and measurements of genetic differences between populations.  

What factors are used to determine if a population represents an important component in the evolutionary legacy of the species?

This second criterion would be met if the population contributed substantially to the ecological/genetic diversity of the species as a whole.  In other words, if the population became extinct, would this event represent a significant loss to the ecological/genetic diversity of the entire species?  In making this determination, the following questions are relevant:

1. Is the population genetically distinct from other conspecific populations?

2. Does the population occupy unusual or distinctive habitat?

3. Does the population show evidence of unusual or distinctive adaptation to its environment?

Why don't you think that spring-run Chinook salmon are an ESU?

Identifying a spring-run-only Chinook salmon ESU for either the Oregon Coast or Southern Oregon and Northern California Coastal areas would be inconsistent with the NMFS ESU policy, because : 1) of high levels of interbreeding between spring- and fall-run fish in these ESUs and 2) spring-run fish as a group in these ESUs do not form a distinct evolutionary lineage within the species.

What information did NOAA Fisheries consider in deciding whether listing was warranted?

Our decision is based on the best scientific and commercial data available, as required by the ESA. We reviewed materials presented by the petitioners, information we received in response to the 90-day findings, and analyses by scientists from NOAA Fisheries’ Southwest and Northwest Fisheries Science Centers who have expertise in the species.