The Lahontan National Fish Hatchery Complex
Pacific Southwest Region

Fishery Improvement Program
Fishery Biologist

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

Stocking LCTThe 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.

Walker LakeCurrently 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.

Incubation boxesAcclimation 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 Biologist at workReservoir.  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

LCT FryThe 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.

Fishery Biologists

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. 

Fishery BiologistsUnderstanding 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.

 

Fishery Biologists
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. 
Fishery Biologists
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.

measuring LCTLCT 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.
Tui Chub
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.

water studiesDistribution 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.

Angler
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. 
Last updated: March 10, 2010