Enhanced Monitoring of the Moberly Lake Trout Rehabilitation Program - - PowerPoint PPT Presentation

Enhanced Monitoring of the Moberly Lake Trout Rehabilitation Program

Ministry of Forests, Lands, Natural Resource Operations and Rural Development Project Leads: Rick Elsner (Brendan Anderson, Lynn Avis, Kristen Peck)

Brief History

• 2002 – low population abundance
• 2005 – beginning of mark-recap program
• 2005-2008 – evaluation of habitat suitability
• 2010 – initiate stocking program
• 2012-2016 – three cohorts of juveniles

stocked

Objectives

• 1. Track Lake trout abundance
• 2. Monitor lake trout life history parameters
• 3. Assess the success of rehabilitation cohorts
• 4. Monitor the response of the Lake Whitefish

population

Objective 1: Monitor Lake Trout Total Abundance and population trends

• Mark-recapture

– Marking: Annual spawning shoal targeted netting – Recapture: Spring Littoral Index Netting (SLIN)

Objective 1: Monitor Lake Trout Total Abundance and population trends

• Recapture rates consistently >50%
• Relatively high capture probability for mature males
• Population growth rate 1.02 (95% CI 0.91-1.14)
• Low but non-zero recruitment
• Depressed state equilibrium
• Total population

~360-570 Mature fish based on a 1:1 sex ratio

Year # Mature Males Upper 95% CI Lower 95% CI SE 2014 217 183 251 17 2015 224 185 263 20 2016 230 184 276 23 2017 235 180 289 28

Objective 1: Monitor Lake Trout Total Abundance and population trends

Objective 2: Monitor Lake Trout Life History Parameters

Objective 2: Monitor Lake Trout Life History Parameters

• Survival is high ~90% (Pradel model)
• Males spawn annually, females 1 out of every

2 years (Barker survival analysis)

• Density dependant growth

Objective 2: Monitor Lake Trout Life History Parameters

Objective 3: Monitor survival, growth fitness and reproduction of stocked cohorts

• SLIN
• Opportunistic targeted netting
• Incidental captures during targeted spawner netting

Objective 3: Monitor survival, growth fitness and reproduction of stocked cohorts

Objective 4: Monitor for changes in Lake Whitefish population

• Hydroacoustic survey with gillnet validation
• Initial years of sampling provide baseline
• Monitoring for shifts in abundance

Objective 4: Monitoring cont’d

• 100,000

200,000 300,000 400,000 500,000 600,000 700,000 800,000 2013 2014 2015 2016 2017

Lake Whitefish

a)

• 500,000

1,000,000 1,500,000 2,000,000 2,500,000 2013 2014 2015 2016 2017

Pygmy Whitefish

b)

Accomplishments and Implications for Conservation

• Establishing indexing

approach for whitefish species monitoring

• New record of pygmy

whitefish in BC

Accomplishments and Implications for Conservation

• Development of sustainable

long term core monitoring program

– Population estimates based on male spawning population – Allows for robust population abundance estimates from single sampling session annually – Allows for evaluation of population parameters: survival, recruitment, mortality, population growth rate

Accomplishments and Implications for Conservation

• Evaluate Success of

Rehabilitation Program

• Most rigorous absolute

abundance lake trout estimates in BC

• Potential future

applications for Lake Trout Stock recovery in BC

• Identification of other

depressed LT populations at equilibrium?

Future Directions

• Continue fall spawner

surveys

– Monitor adult male population – Monitor stocked juvenile recruitment

• Next 3-5 years

implement another SLIN/Hydroacoustic survey

Acknowledgements

Egg Take

Hatchery fish Release