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Ponds: Careful of the Fish!
- Dr. Chuck Cichra
Extension Fisheries Specialist
University of Florida / IFAS SFRC - Program of Fisheries & Aquatic Sciences
Ponds: Careful of the Fish! Dr. Chuck Cichra Extension Fisheries - - PowerPoint PPT Presentation
Ponds: Careful of the Fish! Dr. Chuck Cichra Extension Fisheries - - PowerPoint PPT Presentation
Ponds: Careful of the Fish! Dr. Chuck Cichra Extension Fisheries Specialist University of Florida / IFAS SFRC - Program of Fisheries & Aquatic Sciences All Plants Need Water, Light, and Nutrients Aquatic Plants are No Different Algae are
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Aquatic Plants are No Different
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Algae are simply small plants!
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New Ponds are “Clean”
Clear Water Few Algae / Plants
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Over Time – Ponds Become More Fertile, Plants Become More Abundant
Eutrophication = Enrichment ( increased nutrients – P and N ) of a water body Green Water (Algae) Lots of Plants
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Unacceptable – Looks Bad!
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Where Do the Nutrients Come From????
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Natural Phosphate Deposits in Florida (soils)
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Well Water is Often Full of Phosphorus
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Stormwater Ponds are Built to Catch Storm Runoff / Nutrients (P and N)
Lawn fertilizers, leaves, sticks, grass clippings, …
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Fish Feed
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Livestock and Other Agriculture
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Human Waste
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Nutrients = Plants
Algae ( phytoplankton ) Macrophytes ( large plants )
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Water clarity and algae
Water clarity decreases as algae (phytoplankton) increases
Secchi Disk
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Amount of Chlorophyll (algae) in the Water is Closely Related to the Amount of Nitrogen and Phosphorus in the Water Data from 60 Florida Lakes
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Fertilization – Purposeful Addition
- f Nutrients to the Water
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Fish blocknet data on 60 Florida lakes
50 100 150 200 250 Blocknet Total Fish (kg/ha) Trophic State (chlorophyll)
Oligotrophic Mesotrophic Eutrophic Hypereutrophic
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Bird survey data from 48 Florida lakes
50 100 150 200
Oligotrophic Mesotrophic Eutrophic Hypereutrophic
Bird Abundance (kg/km
2)
Trophic State (Chlorophyll)
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Alligator survey data from 60 Florida lakes
10 20 30 40 50 Oligotrophic Mesotrophic Eutrophic Hypereutrophic
Observed Alligators/km Trophic State
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So, is Eutrophication “Good” or “Bad” ?
A ‘natural’ process Can be ‘spend up’ by humans Results in more plants (large / small) and more animals (inverts, fish, birds, etc.) “Good” or “Bad” depends on our personal perspective / view / goal So, “eutrophication” does not mean that a water body is “dead”!
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Water vs Macrophytes
Greener - less macrophytes Browner (more color) – less macrophytes More clay and suspended bottom sediments - less macrophytes Plants grow to ~1.7 x the Secchi depth Pond construction / Pond dyes
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Macrophytes vs Water
More macrophytes – less planktonic algae More macrophytes – less suspended matter Macrophytes affect fish community composition
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Role of Plants as Fish Habitat?
Spawning areas Refuge - cover from predators (fish/birds) Refuge - places for predators to “hold” Food / Feeding areas
- Fish may eat the plants directly
- Many fish can shift their diets from
invertebrates that live on plants to those that live in/on the bottom
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Can get shifts in fish community composition (plants algae)
Blue Tilapia Warmouth Golden Shiner Gizzard Shad
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How Many Plants are Needed?
Too many! Just Enough!
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So if nutrients don’t kill fish, then what causes fish kills?
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A lot of People Believe that Toxins Cause Most Fish Kills
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Aquatic Herbicide Toxicity (ppm)
Expected application rate Bluegill 96-hr LC-50 Copper – low alkalinity 0.5-1.0 0.88 Endothall alkylamine salt 0.1-1.0 0.94 Copper – high alkalinity 0.5-1.0 7.3 2,4-D 0.5-3.0 168 Diquat 0.12-0.37 245 Endothall dipotassium salt 1.0-3.0 343 Fluridone 0.01-0.09 891 Carfentrizone 1.0-3.0 >1000 Glyphosate NA >1000 Imazapyr NA >1000
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Humans Can Directly Cause Fish Kills However, Most Fish Kills are “Natural” Generally due to Low Dissolved Oxygen in the Water
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Sources of Oxygen: Diffusion Agitation Photosynthesis
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Diffusion of Oxygen Into Water
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Response of Fish to Low Oxygen
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Agitation Speeds up Diffusion of Oxygen into Water
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Natural Agitation = Waves
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Man-Made Agitation = Aerators
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( 85-95% of oxygen in ponds / lakes )
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So how much
- xygen
is enough?
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Sometimes the Algae Die!
Lots of Dead Fish!
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Too Many Floating Plants can Block Sunlight and Prevent Pond Mixing
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Effect of Submersed Plants on the Vertical Distribution of Oxygen in the Water Column
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Density Differences due to Water Temperature Differences Prevent Mixing
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Cross-sections
- f Deep and Shallow Lakes
“Bad” Water: High H2S, Low Dissolved Oxygen, High CO2, High BOD
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Summer Thunderstorm!
Pond turnover – water is ‘turbid’
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So, How do we use this Information in Aquatic Plant Management?
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Algae - Should We Spray? How Much? -- Watch the Weather!
Education – If you kill the plants, the nutrients are still there!
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Submersed Plants – Spray Portion
- f Plants, Herbicide Selection,
Time of Year, Aerate -- Weather
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Floating Plants - Use of Herbicides: Partial Treatments, Herbicide Selection, Weather – Bite the Bullet and Spray?
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Floating Plants – Grass Carp: Aerate & Use Herbicides to Improve Efficacy
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Shift between large plants and phytoplankton (algae) – be careful!
Herbicides Grass Carp
Nutrients still in the pond!
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Effects of Drought?
No Water: No Fish!
( Fish stir up bottom sediments and water is hot )
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