Biological Opinions - Bureau of Reclamation

12.3 Environmental Baseline of Coho Salmon in the Action Area
Endangered Species Act regulations define the environmental baseline as “…the past and present
impacts of all Federal, State, or private actions and other human activities in the action area, the
anticipated impacts of all proposed Federal projects in the action area that have already
undergone formal or early section 7 consultation, and the impact of State or private actions
which are contemporaneous with the consultation in process” (50 CFR 402.02). The “effects of
the action” include the direct and indirect effects of the proposed action and interrelated or
interdependent activities “…that will be added to the environmental baseline” (50 CFR 402.02).
Implicit in both these definitions is a need to anticipate future effects, including the future
component of the environmental baseline. Future effects of ongoing Federal projects that have
undergone consultation and of contemporaneous State and private actions, as well as future
changes due to natural processes, are all part of the environmental baseline, to which effects of
the proposed action are added for analysis.
This Environmental Baseline section is organized into two parts. First, NMFS describes the
biological requirements and seasonal periodicity and life history traits of coho salmon within the
action area. Next, NMFS describes the current extinction risk of all five populations in the
Klamath River basin that are affected by the proposed action.
The Klamath River Basin covers approximately 1,531 square miles of the mainstem Klamath
River and associated tributaries (excluding the Trinity, Salmon, Scott and Shasta River subbasins)
from the estuary to Link River Dam. Although anadromous fish passage is currently
blocked at IGD, coho salmon once populated the basin at least to the vicinity of and including
Spencer Creek at river mile (RM) 228 (Hamilton et al. 2005). Today, coho salmon occupy a
small fraction of their historical area (NRC 2004) due to migration barriers and habitat
degradation.
Coho salmon were once numerous and widespread within the Klamath River basin (Snyder
1931). However, the small populations that remain occupy limited habitat within tributary
watersheds and the mainstem Klamath River below IGD (CDFG 2002a, NRC 2004). Coho
salmon use varied freshwater habitat largely based upon life-stage and season (Sandercock 1991,
Quinn 2005). However, habitat use can also be influenced by the quality of existing habitat and
watershed function, factors which likely play a large role in coho salmon survival.
12.3.1 Periodicity of Coho Salmon in the Action Area
The biological requirements of SONCC ESU coho salmon in the action area vary depending on
the life history stage present at any given time (Spence et al. 1996, Moyle 2002). In the action
area for this consultation, the biological requirements for SONCC ESU coho salmon are the
habitat characteristics that support successful adult spawning, embryonic incubation, emergence,
juvenile rearing, migration and feeding. Generally, during salmonid spawning migrations, adult
salmon prefer clean water with cool temperatures and access to thermal refugia, dissolved
oxygen near 100 percent saturation, low turbidity, adequate flows and depths to allow passage
over barriers to reach spawning sites, and sufficient holding and resting sites. Anadromous fish
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