7845

• UCREFRP Catalog Number: 7845
• Author: Miller, W. J. and D. Laiho.
• Title: Final Report, Upper Colorado River Basin Recovery Implementation Program, Feasibility Evaluation Of Non-Native Fish Control Structures.
• USFW Year: 1997.
• USFW - Doc Type: \
• Copyright Material: NO

' 1
3
8 Oth
C
t
l T
i
h
.
.
er
on
ro
ques
ec
n
1.3.8.1 Management Options

' Management of reservoir levels can be an effective technique for escapement control. In most
western states and most water storage projects in those states, water is a valuable commodity and
proposed changes in water level manipulation may have an impact on water supply and/or water cost
which must be considered as an escapement prevention cost. For instance, a restructured winter
water level which reduces storage may not adversely impact water for agriculture as long as it can be
restored by spring runoff, but may impact water needed for municipal/industrial consumption, the
monetary values of which may differ.
'
Management techniques which have potential application are highly dependent on the individual
dam/reservoir purpose and physical facilities. A variety of physical management techniques have
' been used with different levels of success, including:
1. Low level, cold water release from the part of a reservoir where target fish are least likely to be
' present; this may involve building larger primary outlet works.
2. Restrict maximum normal operating level to below the lip of the service spillway, passing all
routine flow through the more controlled primarily outlet; this reduces spillway screening
' requirements; this may involve building larger primary outlet works.
3. Establish and implement outlet release operating rules (versus unselected default flow releases)
which minimize spills..
4. Completely dry up stream below dam; divert all released flow off stream for fish handling flow,
' screening infiltration, etc. before returning to stream, causing splash and minor flow passage to
fall into a non-viable aquatic environment; this is probably not a suitable ecologic alternative for
the subject applications.
' 5. Periodic drawdowns of water surface to route maximum flow volume through primary outlet and
to control fish (concentrate them for inventory, sorting, and/or removal); leave spawning areas
dry ( keep spawning areas inaccessible, etc.); and establish controlled ecologic conditions
' (temperature, dissolved oxygen, and thermocline).
' Fishery management in the reservoir and stream can also be effective, including:
1. Manage for non-competing warm water fish. Non-competing fish, in terms of endangered
species in the system, would be fish species that prefer lakes and reservoirs rather than riverine
' environments. This list of species includes largemouth bass, bluegills and some crappie.
Species that would compete and are known to exist in the rivers are smallmouth bass and channel
catfish. Fish management should avoid the latter two species to avoid competition if there is
escapement. Largemouth bass can provide an alternative to smallmouth bass for sport fishing
and will not do well in the river systems. Adults may persist but there is little evidence of any

' reproduction and recruitment for largemouth bass in the rivers. Similarly, bluegill seem to do
well in the lakes but do not persist in the downstream environments once they leave the lakes.
2. In conjunction with reservoir operations, timing of draw downs to reduce spawning success of
competitive species may also be an option. This could include dewatering spawning areas
immediately after nests are built and eggs are deposited to reduce the spawning success and
habitat availability. These fluctuations can lower spawning success and lower the amount of

Control Structure Feasibility Evaluation 1-26
' Miller Ecological Consultants, Inc., February 18, 1997