Assessing Crayfish Habitat Dan O’Brien John Meredith Leroy Mims.
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Transcript of Assessing Crayfish Habitat Dan O’Brien John Meredith Leroy Mims.
![Page 1: Assessing Crayfish Habitat Dan O’Brien John Meredith Leroy Mims.](https://reader034.fdocuments.in/reader034/viewer/2022051417/5697bff51a28abf838cbd61b/html5/thumbnails/1.jpg)
Assessing Crayfish Habitat
Dan O’Brien
John Meredith
Leroy Mims
![Page 2: Assessing Crayfish Habitat Dan O’Brien John Meredith Leroy Mims.](https://reader034.fdocuments.in/reader034/viewer/2022051417/5697bff51a28abf838cbd61b/html5/thumbnails/2.jpg)
• 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?
Problem Statement
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Project Overview
Aquatic Vegetation
Sinuosity
Floodplain Width
Riverbed
Proportion Of Watershed Development
•Native Crayfish •Invasive Crayfish
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EVALUATE
Data Sources
FloodplainWidth
AquaticVegetation
Proportion of WatershedDevelopment
Riverbed
River Sinuosity
Crayfish
•Methods
•Results
•Improvements
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Methods: Aquatic Vegetation
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MethodsAquatic Vegetation
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MethodsAquatic Vegetation
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MethodsAquatic Vegetation
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MethodsAquatic Vegetation
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(1) 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
MethodsSinuosity
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Methods
(1) Determine
field sites
(2) Measure
floodplain width
perpendicular
to the river channel
Floodplain
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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.
SoilsMethods
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1. Create a buffer around the sampled sites.2. Select the land use types found in proximity to the crayfish.3. Determine if there is a difference in suitable habitat between the two species.
Land-useMethods
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Results
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No significant difference (p=.84)
0.001.002.003.004.005.006.007.008.00
CRAYFISH
Perc
enta
ge
CATCH NO CATCH
No basis for comparison
0.00
2.00
4.00
6.00
8.00
CRAYFISH
Perc
enta
ge
NATIVE INVASIVE
ResultsAquatic Vegetation as a Percent of Surface Area within 100 meters of Field Sites
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No significant difference in sinuosity (p=.16)
Results
Difference in Average Sinuosity
1.25
1.3
1.35
1.4
1.45
1.5
1.55
CRAYFISH
Sin
uo
sity
NATIVE
INVASIVE
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Significant difference in Floodplain width (p=.049)
Results
Difference in Average Floodplain Width
0
100
200
300
400
500
600
CRAYFISH
Wid
th (
m)
NATIVE
INVASIVE
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Results
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)
Number of field sitesfor each species containing any soil-type
with the following classification.
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Results
AGRICULTURAL AND MIXED URBAN OCCURENCES
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Ag
ricu
ltu
re a
nd
mix
ed U
rban
Per
cen
t
NATIVE
INVASIVE
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 onesite 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 tocompare 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 O’Brien
John Meredith
Leroy Mims