Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Environmental Baseline
capture rates for coho salmon have been reduced from a high of 80 percent to a
low of 5 percent in recent years in non-tribal fisheries now directed at Chinook
salmon (NMFS 2002 BO). Poor and uncertain hatchery practices in the past also
continue to have lingering adverse effects on natural-origin populations in the
ESU. For example, stock transfers from outside of the Klamath River Basin,
which did occur in the past, might change the genetic bases or phenotypic 16
expression of life-history characteristics in a natural population in such a way that
the population might seem either less or more distinctive than it was historically.
Timber harvest activities, associated road construction, grazing, and mining
activities have degraded adjacent aquatic habitat conditions. This was
acknowledged in the Northwest Forest Plan (USDA and USDI 1994 as cited in
NMFS 2002 BO), which guides present and future Federal land management
activities in the Klamath River Basin.
Water was diverted and pumped for use in sluicing and hydraulic mining
operations have also contributed to the decline in coho salmon. Mining
operations can result in dramatic increases in turbidity levels and physical
alterations of the streambed altering stream morphology. The negative impacts of
stream sedimentation on fish abundance from mining were observed as early as
the 1930s.
Water management throughout the Klamath River Basin has altered the historical
hydrology. The magnitude and timing of water flows has significantly changed in
the Trinity, Shasta, and Scott Rivers and in the main stem of the Klamath River.
Agricultural activities, including return flows from irrigation, are also known to
increase nutrient loading through runoff into adjacent streams. These activities
have likely resulted in adverse effects to coho salmon as well as other fish
species, including other salmonids.
Climate variability also plays a large role in driving the fluctuations in salmon
abundance by influencing their physical environment, the availability of food, the
competitors for that food, and the predators that prey on salmon.
Harvest, hatchery practices, land use, water management, and climate variability,
including ocean conditions, have all contributed to declines in coho salmon
abundance throughout the West Coast. These components will be discussed in
more detail below.
16 Phenotype may be defined as the characteristics shown in an individual of the genetic traits
it inherited.
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