Demography of southern leathersidechub in the presence and absence of an introduced predator

Mark C. Belk, Eric Billman, Josh Rasmussen, Karen Mock, Jerald B.

Johnson

Predation – complex effects, experimental approaches

Transition matrix – a powerful tool

• Vital rates and matrix methods• Combine matrix models with predation

experiments • Unravel ecological and evolutionary

consequences of predation

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

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, s0, survival of

offspring from birth to first counting (1 year), applied to fecundity estimates

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?

Survival estimates

No-predator – Salina Creek

Predator – Lost Creek

Stage

juvenile young adult old adult

Sur

viva

l

0.0

0.2

0.4

0.6

0.8

1.0no predator, Salina Creekpredator, Lost Creek

s0 = 0.0014s0 = 0.0033

Juveniles Young adults

Old adults

Juveniles S1 F2 F3Young adults G1 S2Old adults G1,2 G2 S3

1 2 3

F2 F3

G1G1,2G2

S2S3

Life cycle and transition matrix

S1

Juveniles Young adults Old adults

Juveniles 0.0168 1.4497 3.6925Young adults 0.5376 0.2688Old adults 0.0056 0.2112 0.58

No-predator, Salina Creek

Juveniles Young adults Old adults

Juveniles 0.0688 2.2771 7.687Young adults 0.284 0.162Old adults 0 0.1345 0.29

Predator, Lost Creek

Transition matricesJuveniles Young adults Old adults

Juveniles S1 F2 F3Young adults G1 S2Old adults G1,2 G2 S3

Demographics

No predator, Salina Creek

Predator, Lost Creek

Population growth rate 1.32 1.12

Net reproductive rate 2.52 1.36

Generation time 3.32 2.76

Growth rates of individuals

30

40

50

60

70

80

90

100

1 2 3 4

Age (years)

Stan

dard

leng

th (m

m)

No predator, Salina Creek

predator, Lost Creek

Billman et al. 2011, Eco. Fresh. Fish

Demographics

0

0.2

0.4

0.6

0.8

Juvenile Youngadult

Old adult

Prop

ortio

n of

pop

uula

tion

no predatorpredator

Juveniles Young adults Old adults

Juveniles 0.004274 0.188293 0.143655Young adults 0.324856 0.082933Old adults 0.007092 0.136563 0.112335

No-predator, Salina Creek

Juveniles Young adults Old adults

Juveniles 0.02418 0.237917 0.130575Young adults 0.368492 0.062489Old adults 0 0.130575 0.045772

Predator, Lost Creek

Elasticity analysisJuveniles Young adults Old adults

Juveniles S1 F2 F3Young adults G1 S2Old adults G1,2 G2 S3

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 s0 component of fecundity.

Conclusions

• Which vital rates have the greatest impact on population growth and fitness? – Early growth and fecundity contribute most to

population growth and fitness

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