Jose Montoya, Dr' Roelke, and Dr' Winemiller

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Effects of Semaprochilodus kneri on benthic algae
biomass in the Cinaruco River System
Presented by Jennifer Snider
Jose Montoya, Dr. Roelke, and Dr. Winemiller
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Cinaruco River
Orinoco River
Cinaruco River (main channel)
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Monomodal Flooding Pattern
Laguna Larga
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Low water
High water
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Semaprochilodus kneri
Migrates

• Rio Cinaruco
• Low Water
• Rio Orinoco
• High Water

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The Experiment
Effect of S. kneri on the System
Water level
Strong top-down effect
Strong bottom-up effect
Fish density
Weak bottom-up effect
June
March
October
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• March 2003 Experiments
• 10 sites in Lagoons
• 9 sites in Rivers

• May 2003 Experiments
• 10 sites in Lagoons
• 10 sites in Rivers

Sample Locations
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Treatments

• Large Fish Exclosure (LFE)
• Total Fish Exclosure (TE)
• Control (OS)
• Semaprochilodus kneri (SK)

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Artificial Substrate
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Techniques

• Chlorophyll-a
• Benthic algae biomass

• Ash Free Dry Weight
• Organic matter content

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Chlorophyll-a and Phaeophytin Extraction
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Ash Free Dry Weight
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Why Perform these Tests?

• Measuring Chlorophyll-a illustrates the effect of
  S. kneri on benthic algal mass
• Measuring the Ash Free Dry Weight of sediments
  describes the effect of S. kneri on organic
  matter

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Results
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March Low Water
a
p0. 000
p0. 000
a
a
a b
b
c
b
b
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March
17
May High Water
a
a
p0. 853
p0. 171
a
a
a
a
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May
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Effects of S. kneri

• March statistic results
• SKltOS, LFE, TE
• S. kneri lowered the amount of benthic algae mass
  in the studied area
• TEltOS
• May no statistical difference
• LFE, OS, TE
• The small fish have little effect on the benthic
  algae mass (S. kneri not present in system)

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Recognition

• Jose Montoya
• Dr. Roelke
• Dr. Winemiller
• Ellizabeth Fejes

Thanks!