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Demography of southern leatherside chub in the presence and absence of an introduced predator Mark C. Belk, Eric Billman, Josh Rasmussen, Karen Mock, Jerald B. Johnson
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Predation – complex effects, experimental approaches
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Transition matrix – a powerful tool Vital rates and matrix methods Combine matrix models with predation experiments Unravel ecological and evolutionary consequences of predation
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Southern leatherside chub (Lepidomeda aliciae) serial mark-recapture experiment on two populations of southern leatherside chub – one that co-occurs with introduced brown trout and one without
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Stage-structured model Serial mark-recapture, 2 locations, 3-4 years, 3-stages based on size and maturity Fecundity estimates based on independent samples Pre-breeding census model, s 0, survival of offspring from birth to first counting (1 year), applied to fecundity estimates
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Three questions Are there detectable differences in mortality rate between brown trout and non-brown trout environments? What are population demographic consequences of brown trout predation? Which vital rates have the greatest impact on population growth and fitness?
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Survival estimates No-predator – Salina Creek Predator – Lost Creek s 0 = 0.0014 s 0 = 0.0033
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JuvenilesYoung adults Old adults JuvenilesS1F2F3 Young adultsG1S2 Old adultsG1,2G2S3 1 2 3 F2F3 G1 G1,2 G2 S2 S3 Life cycle and transition matrix S1
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JuvenilesYoung adultsOld adults Juveniles 0.01681.44973.6925 Young adults 0.53760.2688 Old adults 0.00560.21120.58 No-predator, Salina Creek JuvenilesYoung adultsOld adults Juveniles 0.06882.27717.687 Young adults 0.2840.162 Old adults 00.13450.29 Predator, Lost Creek Transition matrices JuvenilesYoung adultsOld adults Juveniles S1F2F3 Young adults G1S2 Old adults G1,2G2S3
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Demographics No predator, Salina Creek Predator, Lost Creek Population growth rate 1.321.12 Net reproductive rate 2.521.36 Generation time 3.322.76
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Growth rates of individuals Billman et al. 2011, Eco. Fresh. Fish
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Demographics
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JuvenilesYoung adultsOld adults Juveniles 0.0042740.1882930.143655 Young adults 0.3248560.082933 Old adults 0.0070920.1365630.112335 No-predator, Salina Creek JuvenilesYoung adultsOld adults Juveniles 0.024180.2379170.130575 Young adults 0.3684920.062489 Old adults 00.1305750.045772 Predator, Lost Creek Elasticity analysis JuvenilesYoung adultsOld adults Juveniles S1F2F3 Young adults G1S2 Old adults G1,2G2S3
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Conclusions Are there detectable differences in mortality rate between brown trout and non-brown trout environments? – YES. Pattern is stage-specific and alternates What are population demographic consequences of brown trout predation? – change in λ, stable stage distribution, T – mainly through modification of growth rates (G) and the s 0 component of fecundity.
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Conclusions Which vital rates have the greatest impact on population growth and fitness? – Early growth and fecundity contribute most to population growth and fitness
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Application For fisheries, humans act as predator – Potential for strong ecological effects Introduced fish – Population demography as tool – e.g. effect of burbot on important fisheries species Native species conservation – Effect of introduced species – Effect of habitat degradation – Interacting effects
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