Methodology

SPECIES STATUS ASSESSMENT

For the State of the Salmonids II: Fish in Hot Water report, the following methods were used to assess the status of all 32 kinds of salmon, steelhead, and trout in California.

SELECTION OF SPECIES

The research team used species, subspecies, Evolutionary Significant Units (ESUs), or Distinct Population Segments (DPSs) - taxonomic categories already recognized by state and federal natural resource agencies for management as “species.”

The research team also recognized a few distinct life history variants of Chinook salmon and steelhead (e.g., summer steelhead) that are not yet recognized as distinct entities by all management agencies. They nonetheless possess, in our judgment, sufficient significant evolutionary, ecological, and genetic differences to merit being treated as distinct taxa. This report focuses solely on native California salmonids. It does not include introduced species: Brown trout, Brook trout, Lake trout, Kokanee salmon, or Colorado Cutthroat trout. Dr. Peter Moyle’s laboratory group at UC Davis has been continuously evaluating California’s fish fauna since the first edition of Inland Fishes of California (1976) and the first edition of Fish Species of Special Concern in California (1989). The language has evolved and expanded as research has become available, and this report represents the evolution of those assessments to provide snapshots in time of species status under current trends.

LITERATURE COMPILATION

The research team conducted a literature review to: (1) update information for each taxon; (2) analyze detailed summaries for taxa not adequately treated in previous reviews; and (3) find ‘gray’ literature such as agency administrative reports not used in previous accounts. The team also consulted with over sixty individuals and experts from fishery management agencies familiar with each taxon to obtain unpublished and anecdotal information and gain a better understanding of local conditions.

PRODUCTION OF SPECIES ACCOUNTS

The full, peer-reviewed species accounts, or “main accounts,” are literature reviews with extensive documentation and will be published as Salmon, Steelhead, and Trout in California: Status of Emblematic Fishes, Second Edition.

From these accounts, the research team produced condensed accounts that are presented in this report. These condensed accounts necessarily leave out many important details found in the main accounts, and readers should consult the main accounts as the basis for the information where questions arise. Each main account was drafted using a standard format, with sections for species description, taxonomic relationships, life history, habitat, abundance, threats, climate change, status scoring analysis, and conservation recommendations.

All drafts were reviewed and revised by the research team until they were satisfied with the accuracy of the drafts and then underwent a final review by at least one, but in many cases more than one, external biologist familiar with the taxon and its status.

EVALUATION OF STATUS

The status of each species was evaluated using a set of seven criteria scored using the rubric above (click to enlarge). Those scores were then averaged to produce an overall score for each species - the Level of Concern (see table below). A reliability index was provided for each account based on the certainty of available information (see table below).

OVERALL ANALYSIS

The team summarized the status rankings for all 32 taxa and for each of the seven criteria and compared the Level of Concern of all taxa to those found in the first edition of the State of theSalmonids report to determine trends in status.  The comparisons were made using verbal assessments based on the accounts and status scores, rather than comparing the status scores from the two accounts directly. Numerical status scores were not directly compared between years due to: (1) greatly improved metrics for species distribution and abundance; (2) an improved metric for climate change, based on a study by Moyle et al. (2013); and (3) addition of a new metric that quantified anthropogenic effects (below). We decided the two scoring systems were different enough that the scores should not be directly compared, so we instead used the assessment categories from the 2008 report: extinct, critical concern, high concern, moderate concern, and low concern.

Glossary of Terms

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California Trout, Inc.

California Trout, Inc.