Population Dynamics Dan Magoulick Arkansas Cooperative Fish & Wildlife Research Unit Department...

Population Dynamics

Dan Magoulick

Arkansas Cooperative Fish & Wildlife Research Unit

Department of Biological Sciences

University of Arkansas - Fayetteville

Questions

• What factors are most important in determining fish assemblage structure in drying streams?

• What are the effects of predation in drying stream pools?

• What habitats act as refugia and how does refuge use influence fish assemblage structure in drying streams?

• What are the source – sink dynamics in drying streams?

Pre-drying Drying Isolation Post-drying

B

A

IB<EB

IA EA IA>EA

IB EBIB=EB=0

IA=EA=0IA<EA

IB>EB

0

0.1

0.2

0.3

0.4

0.5

0.6

August September

CR

C A

pp

aren

t S

est

imat

es

Pool Riffle

CRC Transition Probabilities

00.050.1

0.150.2

0.250.3

0.35

0.40.450.5

August September

CR

C T

ran

siti

on

Pro

bab

ilit

ies

Pool to Riffle Riffle to Pool

0

50

100

150

200

250

300

350

400

450

July August September

CR

C P

op

ula

tio

n E

stim

ates

Pool Riffle

Central s toneroller

0

0.2

0.4

0.6

0.8

1

July Septem ber

Su

rviv

al R

ate

Pool Rif f le

Central Stoneroller

0

0.2

0.4

0.6

0.8

1

1.2

July Septem ber

Mo

vem

ent

Rat

ePool Rif f le

Central Stoneroller

0200400

600800

100012001400

160018002000

June August October

Po

pu

lati

on

Est

imat

ePool Riff le

Bigeye shiner

0

0.2

0.4

0.6

0.8

1

1.2

July August Septem ber October

Su

rviv

al R

ate

Pool Riffle

Bigeye shiner

0

0.10.2

0.30.4

0.5

0.60.7

0.80.9

1

July August Septem ber October

Mo

vem

ent

Rat

ePool Rif f le

Bigeye shiner

0

200

400

600

800

1000

1200

1400

1600

June July August Septem ber October

Po

pu

lati

on

Est

imat

es

Pool Rif f le

Conclusions• Survival rates in these systems are low and

species-dependent.– S similar between habitats for central stonerollers.– S pools<riffles but both decreased over time.

• Habitat migration rates related to survival.• Pools are important refuge habitats for some fish

species (e.g. central stonerollers).• Reduced habitat area and fish migration can lead to

increased densities which may impact population and community dynamics