Biological Opinions - Bureau of Reclamation

most juveniles. Stream flow diversions could harm salmonids by concentrating or stranding
them in residual wetted areas (Cushman 1985) before they are relocated, or causing them to
move to adjacent areas of poor habitat (Clothier 1953, Clothier 1954, Kraft 1972, Campbell and
Scott 1984). Juvenile coho salmon that are not caught during the relocation efforts would be
killed from either construction activities or desiccation.
Changes in flow are anticipated to occur within and downstream of restoration sites during
dewatering activities. These fluctuations in flow, outside of dewatered areas, are anticipated to
be small, gradual, and short-term, which should not result in any harm to salmonids. Stream
flow in the vicinity of each project site should be the same as free-flowing conditions, except
during dewatering and in the dewatered reach where stream flow is bypassed. Stream flow
diversion and project work area dewatering are expected to cause temporary loss, alteration, and
reduction of aquatic habitat.
Dewatering may result in the temporary loss of rearing habitat for juvenile salmonids. The
extent of temporary loss of juvenile rearing habitat should be minimal because habitat at the
restoration sites is typically degraded and the dewatered reaches are expected to be less than 500
feet per site and no more than a total of 1000 feet per project. These sites will be restored prior
to project completion, and should improve relative to current condition by the restoration.
Effects associated with dewatering activities will be minimized due to the multiple minimization
measures that will be used as described in the section entitled, Measures to Minimize Impacts to
Aquatic Habitat and Species during Dewatering of Projects within Part IX of the Restoration
Manual (Flosi et al. 2010).
12.4.2.1.3 Risk
Juvenile coho salmon that avoid capture in the project work area will die during dewatering
activities. NMFS expects that the number of coho salmon that will be killed as a result of barrier
placement and stranding during site dewatering activities is very low, likely less than one percent
of the total number of salmonids in the project area. The low number of juveniles expected to be
injured or killed as a result of dewatering is based on the low percentage of projects that require
dewatering (i.e., generally only up to 12 percent; NMFS 2012d), the avoidance behavior of
juveniles to disturbance, the small area affected during dewatering at each site, the low number
of juveniles in the typically degraded habitat conditions common to proposed restoration sites,
and the low numbers of juvenile salmonids expected to be present within each project site after
relocation activities.
12.4.2.2 Fish Relocation Activities
All restoration sites that require dewatering will include fish relocation. CDFW personnel (or
designated agents) capture and relocate fish (and amphibians) away from the restoration project
work site to minimize adverse effects of dewatering to listed salmonids. Fish in the immediate
project area will be captured by seine, dip net and/or by electrofishing, and will then be
transported and released to a suitable instream location.
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