Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Evolutionarily Significant Unit (ESU)
It is noted that the boundaries for the Upper Klamath River Population is from the
confluence of Portuguese Creek (river mile 128) and extends upstream to and
includes Spencer Creek (river mile 227). Spencer Creek is upstream of the IGD
(river mile 190). The IGD is currently an upstream barrier to anadromous
salmonid migrations in the main stem of the Klamath River. Thus, that portion of
the boundaries for the Upper Klamath River Population between IGD and
Spencer Creek (approximately 37 miles) is currently unavailable to this
population.
Viable Salmonid Populations (VSP) Guidance
The VSP document (McElhany et al. 2000) describes four key parameters for
evaluating the status of salmonid populations: population size (abundance);
population growth rate (productivity); spatial structure; and, diversity.
(1) Population Size: Generic guidance from the VSP paper suggests that
effective population sizes of less than 500 to 5,000 fish per generation are
at increased risk (McElhany et al. 2000)). The population size range per
generation was converted to an annual spawner abundance range of 175 to
1,750 fish by dividing by three, which is the generation length for the
majority of the Klamath River coho salmon.
(2) Productivity: Productivity is generally understood to be the ratio of the
abundance of juveniles or adults produced in one generation to the
abundance of their parent spawners. Productivity is primarily driven by
habitat quantity, quality, and reproductive fitness.
(3) Spatial Structure: The spatial structure of a population results from a
complex interaction of the genetic and life history characteristics of a
population, the geographic and temporal distribution and quality of
habitat; and the disturbance level of the habitat. Although the
understanding of these interactions is limited, the ability of individuals to
successfully colonize and move through habitat at each subsequent life
stage is essential for population viability.
(4) Diversity: The transfer from parents to offspring (heritability) of certain
biological traits such as age at maturity, growth rate, and the effect of
these traits on each other has been researched and described. As an
example, under certain circumstances, fishing may influence the biological
traits of salmon that return to spawn, and potentially the traits that are
conveyed to their offspring. Diversity in biological traits is important so
that populations can successfully respond to changing environmental
conditions.
172