Habitat Use and Substrate Preference of Eastern Sand Darters in Vermont

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Habitat Use and Substrate Preference of Eastern
Sand Darters in Vermont
http//faculty.juniata.edu/yohn/esdarter.htm

• Shannon OBrien and Douglas E. Facey
• Department of Biology, Saint Michaels College
• Colchester, Vermont USA

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Outline

• Background on the eastern sand darter
• Methods and results from field studies
• Methods and results from the lab experiment
• General conclusions

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Introduction

• Globally rare
• Historical decline in other parts of their range,
  perhaps due to habitat alterations
• Little historical data is available for the
  populations found in Vermont

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Objective

• Field Studies (2001 and 2002)
• Compare the substrate composition and the number
  of Eastern Sand Darters found to determine if
  their distribution was related to the substrate

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Study Sites

• Poultney River (2001)
• southern most part of Lake Champlain
• 1-mile stretch
• Winooski River (2002)
• Near Burlington, VT
• 6-mile stretch

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• Field Methods
• Sampled 10 X 3 m plots in areas that were less
  than 1 m deep
• Substrate sample for each plot
• Recorded number of fish caught for each plot
  focusing on ESD

• Analysis
• Chi square for Poisson distribution to determine
  if randomly distributed

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Analysis

• Separated substrate samples with sieves
• 7 Substrate size categories
• lt.12mm
• 0.12-0.23mm
• 0.23-0.54mm
• 0.54-1.0mm
• 1.0-1.9mm
• 1.9-4.1mm
• gt4.1mm
• Calculated composition by mass for each
  substrate size category

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Results from the Poultney River

• 42 eastern sand darters were found in 19 of the
  99 different plots

http//www.dec.state.ny.us/website/dfwmr/wildlife/
endspec/estsndrt.html
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Results Poultney River

• Chi square(x2) 17.85, P 0.00002 , df1
• Eastern sand darters were not randomly
  distributed according to the Chi square results
  for the Poisson Distribution

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Results Poultney River

• General Trends Between Eastern Sand Darter
  Density and Substrate Composition
• Lowest density in plots with the highest
  percentage of gravel (gt 1.9 mm)
• Density increased as the percentage of gravel
  decreased, in most cases
• The plots with 4 and 6 eastern sand darters had a
  high percentage of fine and medium sand
  (0.12-0.23 mm and 0.23-0.54 mm)

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Results from the Winooski River

• 112 eastern sand darters were found in 12 of the
  56 plots
• Seventy-four of the eastern sand darters were
  caught in one plot

http//www.nanfa.org/meetings/2001/pictures/cs/cs.
htm
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Results Winooski River

• Chi square(x2) 199.2, P 6.07 x 10-43
• Eastern sand darters were not randomly
  distributed according the Chi square results for
  the Poisson Distribution

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Results Winooski River

• General Trends Between Eastern Sand Darter
  Density and Substrate Composition
• Less abundant in areas with a high percentage of
  gravel (gt 1.0 mm)
• Large densities found in areas with a higher
  percentage of medium- sized sand (0.23-0.54 mm)
  and more coarse sand (0.54-1.0 mm)

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Summary of Results

• Eastern sand darters were not randomly
  distributed in either river
• Trends for eastern sand darter distribution and
  substrate composition
• Higher density of fish in areas with low
  percentage of coarse substrate
• Usually a high percentage of medium sized sand in
  areas with more eastern sand darters
• Field studies did not test preference so followed
  up with a lab experiment to test preference

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Objective

• Lab Study (2002)
• Determine if eastern sand darters prefer a
  certain size particle when given a choice of 4
  different sizes within a tank
• Predictions
• Eastern sand darters will show a preference for
  the smaller sized substrate

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Methods for Lab

• Divided the bottom of 4 tanks into 4 equally
  sized rectangles with plastic dividers 2.5 cm
  high
• Filled each rectangle with one of four different
  size particles
• 0.23-0.54 mm, 0.54-1.0 mm, 1.0-1.9 mm, or 1.9
  -4.1 mm
• Each tank had a different orientation of the four
  particle sizes

• Fish were kept for one week and observed daily,
  approximately every 2 hours
• Recorded which size sediment they were over or
  burrowed into
• Performed chi square using the first observation
  made for each fish on their 4th day in the tank
• Determined if eastern sand darters showed a
  preference for burrowing in a substrate
  consisting of a certain sized particle

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Results Lab Study

• A total of 49 fish were observed between August
  2002 and Oct 2002
• Based on a total of 912 observations, eastern
  sand darters were burrowed 790 times (86.6 ) and
  were not burrowed 122 times (13.3 )

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• Eastern sand darters burrowed the most in
  sediment less than 1.0mm (73)

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Chi Square Analysis

• Used first observation made on 4th day for each
  fish that was burrowed (N46)
• Chi square(x2) 19.6, Plt 0.005 , df3
• Showed a statistically significant preference for
  sediment ranging in size 0.23-1.0 mm

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Conclusions

• The Lab results supported the field observations
  from both the Poultney and Winooski Rivers
• Utilize and prefer areas with a high percentage
  of sediment 0.23-1.0 mm in size
• Sediment size influences their distribution
• Indicates they are selective
• Alterations in the sediment of rivers may impact
  their ability to utilize certain habitats

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Acknowledgements

• Thanks to
• The Vermont Nature Conservancy, which generously
  funded the Poultney River Project in 2001
• The Lake Champlain Research Consortium for
  funding both the Poultney and Winooski River work
• The Clare Boothe Luce Scholarship Fund which also
  providing funding for both projects

References Daniels, R.A. 1989. Significance of
burying in Ammocrypta pellucida. Copeia
198929-34. Daniels, R.A. 1993. Habitat of the
eastern sand darter, Ammocrypta pellucida.
Journal of Freshwater Ecology 8 287-295. Facey,
D. E. 1998. Status of the Eastern sand darter
(Ammocrypta pellucida) in Vermont. Canadian
Field-Naturalist 112 596-601