Assessing Crayfish Habitat

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Assessing Crayfish Habitat

• Dan OBrien
• John Meredith
• Leroy Mims

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Problem Statement

• Scientists are observing invasive crayfish
  displacing
• indigenous crayfish in the Lake Mendota
  Watershed.
• Invasive crayfish are thought to disrupt aquatic
  habitat
• for native fish and plants species.
• This project assesses the relationship between
  crayfish
• and their surrounding environmental variables.
  Are there
• trends in environmental habitat?

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Project Overview

• Aquatic Vegetation
• Sinuosity
• Floodplain Width
• Riverbed
• Proportion Of Watershed Development

• Native Crayfish

• Invasive Crayfish

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Data Sources
Aquatic Vegetation
E V A L U A T E

• Methods
• Results
• Improvements

River Sinuosity
Floodplain Width
Proportion of Watershed Development
Riverbed
Crayfish
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Methods Aquatic Vegetation
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Methods
Aquatic Vegetation
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Methods
Aquatic Vegetation
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Methods
Aquatic Vegetation
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Methods
Aquatic Vegetation
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Methods
Sinuosity

• Determine stream segments within each Dane County
  subwatershed
• (2) Measure river-miles for each stream segment
• (3) Compare this length to the minimal distance
  from source to mouth

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Methods
Floodplain

• (1) Determine
• field sites
• Measure
• floodplain width
• perpendicular
• to the river channel

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Methods
Soils
1.Create a buffer around the sampled sites. 2.
Select the Length Slope Factors found in
proximity to the sites. 3. Determine if there is
a difference in tolerance to erosion.
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Methods
Land-use

• Create a buffer around the sampled sites.
• Select the land use types found in proximity to
  the crayfish.
• Determine if there is a difference in suitable
  habitat
• between the two species.

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Results
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Results
Aquatic Vegetation as a Percent of Surface Area
within 100 meters of Field Sites
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Results

• No significant difference in sinuosity (p.16)

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Results

• Significant difference in Floodplain width
  (p.049)

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Results
Number of field sites for each species containing
any soil-type with the following classification.
Length-slope factor NATIVE INVASIVE
A HIGHEST 0 3
B 12 5
C 5 1
D 1 0
E highest 0 1
X2 Analysis (p-value is .20)
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Results
Land-use (p-value.002)
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Conclusion

• For aquatic vegetation, results are inconclusive.
• Results for sinuosity and riverbed substrate were
  promising, but not significant.
• However, for floodplain width and proportion of
  200-m buffer in agriculture or mixed-urban
  land-use, we observed a difference in the habitat
  for invasive crayfish.

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Conclusion

• Floodplain width and proportion of 200-m buffer
  in agriculture or mixed-urban land land-use
• Invasive crayfish inhabit wider floodplains,
  implicating different watershed hydrologies.
• Native crayfish inhabit regions with less
  erodible soil-types - suggests particulate flow
  may be a factor.

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Data Challenges
Tree canopy obstructing rivers at the one site
with Invasive Crayfish
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Data Challenges

• Decision to pursue Aquatic Vegetation from
  Panchromatic QuickBird not made in light of
  field site locations
• Satellite images cut-off too far south to
• compare Invasive against Native Crayfish
• Images only a snapshot of time (July 31, 2004),
• while aquatic vegetation, the riverbanks and
  crayfish vary throughout the season
• Inherent errors built into digitization process
• Manual digitization
• Upstream vegetation

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Data Challenges

• River velocity
• Land-use classification
• Flood-plain

Questions?
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Assessing Crayfish Habitat

• Dan OBrien
• John Meredith
• Leroy Mims