rusty crayfish in sparkling lake 18 years after a removal … · 2019. 4. 19. · • dave balsiger...
TRANSCRIPT
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