Fishery Improvement Program
Links to Fishery Team Actions:
Monitoring
Research
Fishery
In 2005 the passage of Public Law 109-103 under the
Desert Terminal Lakes Program provided funding for
fishery improvements in the State of Nevada with an
emphasis on the Walker River Basin. As a result, the
Walker Lake Fishery Improvement Program (FIP) was formed.
The goals of this comprehensive, partnership-based
program are to improve the survival of the Lahontan
cutthroat trout (LCT) and other native fish in Walker
Lake and lower Walker River and to investigate ecosystem
response to fresh water inflow and changing levels
of total dissolved solids (TDS). All photos on this page are courtesy of the USFWS
The
Fishery Improvement Team (Team), which was formed under
the FIP, includes representatives from the Service,
the Walker River Paiute Tribe, and the Nevada Department
of Wildlife. To help achieve FIP goals, the Team developed
a fisheries improvement plan which has been used to
identify and implement research, monitoring, and fisheries
management actions needed to advance knowledge of the
Walker Lake ecosystem and improve its native fishery.
Currently
the Team is working cooperatively on a number of projects
aimed at understanding how the lake’s ecosystem and
the native fishery are responding to changes in water
level, river flows into the lake, and salinity. We
will provide updates on our research and findings on
this website, and provide links to all reports when
they become available.
Acclimation
of stocked LCT
The
Team has been investigating a variety of methods to
improve acclimation of LCT prior to stocking. These
actions include testing and improving acclimation methods
in a laboratory setting and using river inflow to allow
for self-acclimation in the freshwater area at the
confluence of the Walker River and Walker Lake . Prior
to stocking, the Service works with the Walker River
Paiute Tribe and the Bureau of Indian Affairs to procure
water releases from Weber 
Reservoir. LCT are stocked
into the river just upstream of the lake during these
increased flows. Monitoring of tagged, recaptured LCT
that are stocked on separate dates will help us to
understand which conditions are most favorable for
successful acclimation.
Survival and growth of stocked LCT
The
Team is working with scientists on a 5-year mark-recapture
study using stocked, tagged fish to assess survivorship
and growth of LCT in Walker Lake. Beginning in 2006,
all LCT stocked in Walker Lake were measured and tagged
with individually numbered Floy tags prior to release.
Working cooperatively, the Team employed a variety
of methods to recapture the tagged fish; these included
netting, hook and line sampling, an expanded creel
survey to gather information from anglers, and encouraging
self-reporting of recaptured fish by installing additional
drop boxes near lake access points. In addition, a
hotline telephone number is printed on the tags so
that anglers can call in their catch. Measurements
on recaptured fish are used to ascertain growth, and
tag information is used to determine survival rates
of stocked LCT.
By studying how LCT stocked from the Lahontan National
Fish Hatchery and Mason Valley Hatchery are surviving
, the team is ascertaining what management actions
to take to improve the long-term survivorship of LCT
in the lake. Monitoring growth gives us information
on whether an adequate prey base is available and whether
lake water quality imposes limitations on the performance
of stocked LCT.
Understanding
LCT survivorship and growth under variable lake,
river flow, and salinity levels will assist us
in developing strategies to achieve the goal of restoring
a self-sustaining lake population of LCT.
Limnological monitoring
Concurrent with other projects the Team is monitoring
physical, nutrient, phytoplankton and zooplankton in
Walker Lake. Limnological conditions at Walker Lake
have been measured by many state and federal agencies
and other organizations over many years prior to initiation
of the Desert Terminal Lakes Program. Using this information
as a baseline, the Team expanded limnological monitoring
in 2007. This 5 year project will document changes
in the planktonic community as well as physical and
chemical properties of Walker Lake water under variable
lake, river flow, and salinity levels.
The results of limnological monitoring
will help interpret other changes in the lake, such
as variations in the LCT prey base and LCT survival.
Understanding relationships between the limnological
conditions and the LCT fishery will help us to predict
how changes in Walker Lake surface elevation will affect
the fishery, allowing better management.
LCT
prey items
Two separate projects initiated by the Team are studying
LCT prey items in Walker Lake. The first is a quantitative
measure of the aquatic invertebrates that inhabit the
lake substrate. Previous studies have documented changes
in the invertebrate community composition of Walker
Lake as lake levels dropped. The goals of this study,
which began in 2007, are to document the current distribution
and abundance of invertebrates in the lake. Invertebrates
are a critical resource to LCT both as direct prey
items and indirectly as a food resource to tui chub.
Tui chub are a preferred food item of LCT.
The second project is using hydroacoustic
technology to estimate tui chub densities and population
parameters, such as age distribution and population
size. This project is aimed at both documenting the
current condition of the tui chub population and assessing
the feasibility of using hydroacoustic technology to
monitor changes in the population.
Tui chub, which are native to Walker Lake, are the
most abundant fish in the lake. They are an important
food resource for LCT as well as piscivorous migratory
birds such as loons, pelicans and grebes. Current
and previous monitoring of the Tui chub population
suggests that reproduction has decreased with the increase
in salinity. Learning how the LCT prey base responds
to fluctuating lake levels and salinity will help us
improve the LCT fishery in Walker Lake.
Distribution
of Macrophytes
In addition to assessing tui chub populations, the
Team is investigating the use of hydroacoustic technology
to map the distribution of and monitor changes in Walker
Lake macrophytes. Macrophyte beds are a prominent
feature in the lake and serve as both shelter and food
for invertebrates and tui chub. Macrophytes, like
other Walker Lake inhabitants, are affected by changes
in lake elevation and salinity. Documenting changes
in macrophyte distribution in relation to fluctuating
lake levels will give us further information on how
the lake ecosystem as a whole responds to varying river
inflow.
Creel census
With the long-term goal of improving the native LCT fishery
at Walker Lake , the Team expanded the creel census to determine
seasonal catch rates and assess angler satisfaction. In
addition, information gathered during creel surveys is used
to support ongoing monitoring of survival and growth. Looking
at trends in creel data is another means by which the team
can assess changes in the LCT fishery and assess appropriate
management actions.Angler information is vital to these
ongoing studies. The Team expanded contact with anglers
not only through creel surveys but through installation
of additional self-reporting drop boxes and informational
signs. The Angler Information page on this website provides
additional information on how to report a tagged fish.
