Effects of small reservoirs on downstream crayfish communities

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Effects of small reservoirs on downstream
crayfish communities

• Susan B. Adams
• sbadams_at_olemiss.edu

USDA Forest Service, Southern Research
Station Oxford, Mississippi, USA
Presented at the 16th Symposium of IAA, Gold
Coast, Queensland, Australia, Jul 30 Aug 4, 2006
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USA
Mississippi
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Upstream effects
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Upstream effects
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Downstream effects
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Downstream effects
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Drought recovery study (Adams Warren 2005)
0.5
- no reservoir
- reservoir upstream
0.25
0
pre- drought, summer
Nov- Dec
Jan
April
June
Nov
Month
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Cambarus striatus
?
Procambarus hayi
?
Procambarus ouachitae
?
Procambarus vioscai
Orconectes chickasawae
Hydrology
Oxygen
Temperature
?
Predation
?
Food
Behavior / burrowing
Life history timing
?
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Study Design

• 8 sites
• 4 downstream of reservoirs
• 4 not near reservoirs
• Sites 160 m long ( 40 x mean width), divided
  into 4 subreaches

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Electrofished 1.7 sec / m2 (1100 sec/site)
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Seined 4 hauls/sets per subreach (total 16)
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I.D., measure, release crayfish
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Crayfish density (e-fish seine)
- no reservoir
- reservoir upstream
Number / m2
Month - 2004
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Orconectes chickasawae
Procambarus ouachitae
Cambarus striatus
Procambarus hayi
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Genus composition
- Orconectes
- Procambarus
- Cambarus
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Orconectes density (e-fish seine)
- no reservoir
- reservoir upstream
Number / m2
Aug
Sep
Nov
Month - 2004
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Procambarus density (e-fish seine)
1.8
- no reservoir
- reservoir upstream
1.2
Number / m2
0.6
0.0
Aug
Sep
Nov
Month - 2004
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Procambarus spp. composition- November
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Crayfish sizes over time
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Physical habitat P-values
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Other possible influences

• Substrate more clay below reservoirs
• Leaf accumulation below reservoirs
• Predators more below reservoirs??
• Nutrient differences

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Cumulative Effects
142 Lakes. If effects extend 1 km down- and 1
km upstream of dam, then 284 km of mostly 1st
-3rd order streams influenced by small reservoirs
in upper LT.
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Many thanks to

• The field crew Amy Commens, Clifford Harwell,
  Gordon McWhirter, Kevin Anazia, and Willie
  Shughart
• Amy Commens for measuring a zillion tiny crayfish
  
• Chris Taylor, INHS, for general help on crayfish
  identification.
• Funded by US Forest Service, Southern Research
  Station

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