you are what you eat! · 2018-09-18 · gretchen hansen• university of minnesota. 2018 maisrc...
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Gretchen Hansen• University of Minnesota2018 MAISRC Showcase
Beginning to understand how AIS disrupt sport fisheriesYou are what you eat!
A Collaborative Project
Gretchen HansenTyler AhrenstorffBethany BethkeWill FrenchJodie HirschHeidi Rantala
Ryan MakiKatya KovalenkoValerie BradyJosh DumkeDonn Branstrator
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Gretchen HansenTyler AhrenstorffBethany BethkeWill FrenchJodie HirschHeidi Rantala
Ryan MakiKatya KovalenkoValerie BradyJosh DumkeDonn Branstrator
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Gretchen Hansen
A Collaborative Project
Little Critters, big impacts
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Little Critters, big impacts?
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Minnesota’s Large Lakes
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• Cass• Kabetogama• Lake of the Woods• Leech• Mille Lacs• Rainy• Red• Vermilion• Winnibigoshish
A two pronged approach
• Growth of age-0 walleye and yellow perch
• Most directly affected by reduced zooplankton
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A two pronged approach
• Growth of age-0 walleye and yellow perch
• Most directly affected by reduced zooplankton
• Whole food web analysis of reliance on different energy sources
• More complicated• More potential for indirect effects
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A two pronged approach
• Growth of age-0 walleye and yellow perch
• Most directly affected by reduced zooplankton
• Whole food web analysis of reliance on different energy sources
• More complicated• More potential for indirect effects
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Bigger is Better
Larger fish:• Eat a wider variety of prey
• Can escape predators better
• Have more energy reserves for winter
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Do zebra mussels or spiny waterflea affect fish growth?
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• Walleye & yellow perch (age-0)• Historical data from DNR
sampling• Compare size pre-and post
invasion• Standardize for temperature
How do we compare fish growth?
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Fish
size
Smal
lBi
g
Date OctoberMay
Seasonal growth
How do we compare fish growth?
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Fish
size
Smal
lBi
g
Date
Year 2
OctoberMay
Year 1
How do we compare fish growth?
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Fish
size
Smal
lBi
g
Degree Days
Date OctoberMay
Temperature WarmerCooler+
How do we compare fish growth?
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Fish
size
Smal
lBi
g
Degree Days
No difference
Date OctoberMay
Temperature WarmerCooler+
Uninvaded
How do we compare fish growth?
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Date
Fish
size
OctoberMay
Smal
lBi
g
Temperature WarmerCooler+
Degree Days
Invaded
Same starting size, different growth rate
No differenceUninvaded
How do we compare fish growth?
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Date
Fish
size
OctoberMay
Smal
lBi
g
Temperature WarmerCooler+
Degree Days
Uninvaded
Invaded Same starting size, different growth rate
No difference
Different starting size, same growth rate
How do we compare fish growth?
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Date
Fish
size
OctoberMay
Smal
lBi
g
Temperature WarmerCooler+
Degree Days
Invaded
Same starting size, different growth rate
No difference
Different starting size, same growth rate
Different starting size, different growth rate
Uninvaded
Preliminary results: Walleye growth
Smaller starting size, slower growth rate
Smaller starting size, same growth rate
Spiny water flea
Zebra mussels
7.7 inches
5.9 inches
7.0 inches
Degree Days
Preliminary results: yellow perch growth
Spiny water flea
Zebra mussels
Bigger starting size, slower growth rate
No difference
3.1 inches
2.6 inches
Degree Days
Growth varies a lot among lakes and years
A two pronged approach
• Growth of age-0 walleye and yellow perch
• Most directly affected by reduced zooplankton
• Whole food web analysis of reliance on different energy sources
• More complicated• More potential for indirect effects
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Tissues tell a story
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Tissues tell a story
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Tissues tell a story
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Tissues tell a story
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Offshore Carbon
Nitrogen
Trop
hic
Leve
lNearshore Carbon
Tissues tell a story
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Offshore Carbon
Nitrogen
Trop
hic
Leve
lNearshore Carbon
Tissues tell a story
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Offshore Carbon
Nitrogen
Trop
hic
Leve
lNearshore Carbon
Tissues tell a story
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Nitrogen
Trop
hic
Leve
lNearshore Carbon
Tissues tell a story
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Offshore Carbon
Nitrogen
Trop
hic
Leve
lNearshore Carbon
Tissues tell a story
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Offshore Carbon
Nitrogen
Trop
hic
Leve
lNearshore Carbon
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3,064 samples and counting
Preliminary results: Mille Lacs food web
33Offshore Carbon
Trop
hic
Leve
l
Nearshore Carbon
Preliminary results: Mille Lacs food web
34Offshore Carbon
Trop
hic
Leve
l
Nearshore Carbon
Preliminary results: young of year walleye
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Nearshore Carbon
Offshore Carbon
What’s next?
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• Additional growth data collected in 2018
• Food web data from all 9 lakes• What inferences can we make
about individual lakes? Lakes in general?
• Ongoing research and management partnerships
Informing Management
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• What can we expect to happen to walleye when an invasive is found?
• Do small changes in first year growth of walleye affect later survival/growth/populations?
• Do the effects vary by lake?• Is there a key component of a
lake that helps to buffer against AIS effects?
Thanks!• Funding
• MAISRC• Environmental and Natural Resources
Trust Fund• Federal Aid - Sport Fish Restoration
• Field work• Large Lake Staff
• MN DNR and Red Lake DNR
• Voyageurs National Park staff• MN DNR interns
• Sierra Mabanta, Nic Brown, Madeline Humphrey
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More about isotopes
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Heavy and Light Atoms
Carbon – 12 Carbon – 13
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Isotopes are Naturally Occurring
42Stable Isotope Ecology Brian Fry
“Heavy” and “Light” Atoms
13C• A regular Carbon atom has:
• 6 Electrons• 6 Protons• 6 Neutrons• An atomic mass of 12 (12C)
• A carbon isotope has:• 6 Electrons• 6 Protons• 7 Neutrons• An atomic mass of 13 (13C)
15N• A regular Nitrogen atom has:
• 7 Electrons• 7 Protons• 7 Neutrons• An atomic mass of 14 (14N)
• A carbon isotope has:• 7 Electrons• 7 Protons• 8 Neutrons• An atomic mass of 14 (14N) 43
Other invasive species
• Rusty Crayfish• Banded Mystery Snails• Starry Stonewort
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Potential impacts
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Potential impacts
Or… ?
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Minnesota’s Large Lakes
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• Cass• Kabetogama• Lake of the Woods• Leech• Mille Lacs• Rainy• Red• Vermilion• Winnibigoshish
Minnesota’s Large Lakes
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• Cass• Kabetogama• Lake of the Woods• Leech• Mille Lacs• Rainy• Red• Vermilion• Winnibigoshish
Minnesota’s Large Lakes
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