Biological Opinions - Bureau of Reclamation

12.4.2.2.1 Exposure
Because fish relocation occurs immediately prior to or during dewatering, the life stage most
likely to be exposed to fish relocation are also juvenile coho salmon.
12.4.2.2.2 Response
Fish relocation activities may injure or kill rearing juvenile coho salmon because these
individuals are most likely to be present in the restoration sites. Any fish collecting gear,
whether passive or active (Hayes 1983) has some associated risk to fish, including stress, disease
transmission, injury, or death. The amount of injury and mortality attributable to fish capture
varies widely depending on the method used, the ambient conditions, and the expertise and
experience of the field crew. The effects of seining and dip-netting on juvenile salmonids
include stress, scale loss, physical damage, suffocation, and desiccation. Electrofishing can kill
juvenile salmonids, and researchers have found serious sublethal effects including spinal injuries
(Reynolds 1983, Habera et al. 1996, Habera et al. 1999, Nielsen 1998, Nordwall 1999). The
long-term effects of electrofishing on salmonids are not well understood. Although chronic
effects may occur, most effects from electrofishing occur at the time of capture and handling.
Most of the stress and death from handling result from differences in water temperature between
the stream and the temporary holding containers, dissolved oxygen levels, the amount of time
that fish are held out of the water, and physical injury. Handling-related stress increases rapidly
if water temperature exceeds 18 °C or dissolved oxygen is below saturation. A qualified
fisheries biologist will relocate fish, following both CDFW and NMFS electrofishing guidelines.
Because of these measures, direct effects to, and mortality of, juvenile coho salmon during
capture will be greatly minimized.
Although sites selected for relocating fish will likely have similar water temperature as the
capture site and should have ample habitat, in some instances relocated fish may endure shortterm
stress from crowding at the relocation sites. Relocated fish may also have to compete with
other salmonids, which can increase competition for available resources such as food and habitat.
Some of the fish at the relocation sites may choose not to remain in these areas and may move
either upstream or downstream to areas that have more habitat and lower fish densities. As each
fish moves, competition remains either localized to a small area or quickly diminishes as fish
disperse.
Fish relocation activities are expected to minimize individual project impacts to juvenile coho
salmon by removing them from restoration project sites where they would have experienced high
rates of injury and mortality. Fish relocation activities are anticipated to only affect a small
number of rearing juvenile coho salmon within a small stream reach at and near the restoration
project site and relocation release site(s). Rearing juvenile coho salmon present in the immediate
project work area will be subject to disturbance, capture, relocation, and related short-term
effects. Most of the effects associated with fish relocation are anticipated to be non-lethal.
However, a very low number of rearing juvenile coho salmon captured may be injured or killed.
In addition, the number of fish affected by increased competition is not expected to be significant
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