Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Evolutionarily Significant Unit (ESU)
NMFS stated that few of the biological characteristics examined provide
information useful for developing and understanding the historical population
structure of SONCC coho salmon ESU populations (p. 17 and p. 18, NMFS
2006). The genetic data provide support for an isolation-by-distance view of
population structure, although finer resolution of the population structure from
genetic data was not available (NMFS 2006). Information on dispersal rates, life
history and phenotypic traits, and population dynamics are also not generally
available for the SONCC coho salmon ESU. Where this information is available,
NMFS concluded that often it is not collected at a large enough spatial scale
useful for distinguishing populations. In addition, the lack of time series and the
tendency of many of the characteristics to be highly variable (e.g., run timing,
jacking rate 13 , etc.) and often attributable to environmental variation limit their
use for distinguishing populations (NMFS 2006).
Population size, dispersal rates, life-stage specific survival rates, and fecundity
data are not available for populations in the SONCC coho salmon ESU (p. 10,
NMFS 2006). NMFS therefore focused on measures of historical habitat carrying
capacity, as a metric of population viability. However, as noted earlier, Brown et
al. (1994) pointed out that all of these historical estimates are “guesses” that
fishery managers and biologists have generated using a combination of limited
catch statistics, hatchery records, and personal observations. NMFS
acknowledged that the analysis of population structure was strongly constrained
by the lack of available data (p. 42, NMFS 2006).
Identified Populations within the SONCC Coho Salmon ESU
NMFS has recognized that our understanding of the current status of coho salmon
in this region is imprecise and that available data is sparse and provides a poor
foundation for rigorous analysis of the processes that influence these populations.
In place of detailed, local information, NMFS drew on data and analyses
developed elsewhere and applied what has been learned to similar situations in the
SONCC coho salmon ESU (p. 43, NMFS 2006).
The geographic setting of the SONCC coho salmon ESU includes three large
basins and numerous smaller basins across a diverse landscape. The Rogue River
and Klamath River extend beyond the Coast Range and include the Cascade
Mountains. For the Rogue River, Klamath River, and Eel River basins of the
SONCC coho salmon ESU, the approach NMFS used to determine populations
13 Jacking rate is defined as the proportion of adult coho salmon from a brood that return as
jacks. Jack is defined as a coho salmon that matures at age 2 and returns from the ocean to spawn
a year earlier than normal. Jacks are all male fish.
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