Rusty Crayfish in Sparkling Lake 18 Years After a Removal Experiment

Katie Hein

Rusty Crayfish Distribution

NativeInvaded

Impacts of rusty crayfish

• Extirpation of native crayfish species

• Negative effects on:

• macrophytes

• macroinvertebrates

• recreational fish

Low crayfish abundance

High crayfish abundance

Brian Roth

Karen Wilson

Rusty Crayfish Removal Experiment

• Is it possible to reduce/extirpate rusty crayfish?

• Are negative effects of rusty crayfish reversible?

• Can fish control rusty crayfish once trapping has reduced their population to low levels?

Sparkling Lake

• Small (64 ha)

• No surface inlets or outlets

• Rusty crayfish present since the 1970’s

• Long-term records available (1981 – present)

Rusty Crayfish Removal

Trap adultsFish predation

on small crayfish

Smallmouth Bass• Size limit from 14” to 18”

• Bag limit: 1 fish/person/day

•June-August 2001-2008•100-300 traps per day•1,300-15,000 “trap days” per year•91,930 crayfish removed

Trapping effort was high

Hein et al. 2006 Can J Fish Aquatic SciHein et al. 2007 Freshwater Biology

Rusty crayfish declined by 99%

Rusty Crayfish

Virile Crayfish

CP

UE

(cra

yfis

h/t

rap

*day

)

1980 1985 1990 1995 2000 2005

Removal Begins

0.00

0.25

0.50

0.75

0

5

10

15

Virile Rusty

Short Term Success!

1. Extirpate rusty crayfish

2. Fish predation maintains low densities

3. Rusty crayfish rebound when removal stops

Brian Roth

What will be the long-term success of removal?

Population model suggested long-term possibility of success

0 0.1 0.2 0.3 0.4

-2

-1.5

-1

-0.5

0

0.5

Proportion of the populationremoved

Pop

ula

tio

n g

row

th r

ate

(r)

FishTraps

Hansen et al. 2013 EcologyHansen et al. 2013 Can J Fish Aquatic Sci

Rusty crayfish declined by 99% and stayed low

Periods

Rusty Crayfish

Virile Crayfish

CP

UE

(cra

yfis

h/t

rap

*day

)

1980 1985 1990 1995 2000 2005

Removal Period

0.00

0.25

0.50

0.75

0

5

10

15

Hansen et al. 2013 EcologyHansen et al. 2013 Can J Fish Aquatic Sci

Rusty crayfish declined by 99% and stayed lowNative (virilis) crayfish increased 100x

Rusty Crayfish

Virile Crayfish

CP

UE

(cra

yfis

h/t

rap

*day

)

1980 1985 1990 1995 2000 20050.00

0.25

0.50

0.75

0

5

10

15

Removal Period

2010 2015

Rusty Crayfish Removal Experiment

• Is it possible to reduce/extirpate rusty crayfish?

YES but it requires a lot of effort

• Are negative effects of rusty crayfish reversible?

Sparkling Lake ecosystem response

Macrophyte percent cover increased, especially in deeper water

“High crayfish” “Low crayfish”

Sunfish (Lepomis) Increased

Removal Period

Cat

ch/e

ffo

rt

1980 1985 1990 1995 2000 2005

0

20

40

60

2010 2015

Bass Abundance Stayed the Same

Lepomis

Smallmouth

Rock bass

Mark-recapture population estimate

Bass ate more invertebratesRock Bass Smallmouth Bass

CrayfishInvertebratesZooplankton FishOther

Variety of Macroinvertebrate Abundance Responses

Snails

Dragonflies

Mayflies

Scuds

Pavel Beracko

Jim Rathert

Declined Increased

Before Removal

After Removal

Rusty Crayfish Removal Experiment

• Is it possible to reduce/extirpate rusty crayfish? YES

• Are negative effects of rusty crayfish reversible?YES, with variable effects on macroinvertebrates

• Can fish control rusty crayfish once trapping has reduced their population to low levels?

Lake level declined during removal REMOVAL

Drought reduces cobble rearing habitat

for rusty crayfish

Rusty Crayfish Removal Experiment

• Is it possible to reduce/extirpate rusty crayfish? YES

• Are negative effects of rusty crayfish reversible? YES

• Can fish control rusty crayfish once trapping has reduced their population to low levels?

SO FAR. Possible effects of water levels on habitat

Acknowledgements

• NSF – REU, Biocomplexity, and LTER grants• Jake Vander Zanden and lab• Gretchen Hansen• Martin Perales• Brian Roth• Steve Gilbert • Dave Balsiger• Barbara Benson• Jeff Maxted• Karen Wilson• Stacy Lischka• Adam Ray• Ellen Feingold• Patrick Hermann• Laura Kessler• Julia McCarthy• Katie Lord• Everyone who got “pinched”

Center for Limnology, UW-Madison