Offflavor Management - PowerPoint PPT Presentation
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Offflavor Management
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Modify chemical, physical, or biological environments to discourage blue-green algal growth ... Fathead minnows are omnivorous but consume algae ... – PowerPoint PPT presentation
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Title: Offflavor Management
1
Off-flavor Management
- Gary Burtle
- Animal Dairy Science
- University of Georgia
2
Off-flavor Problem
- Linked primarily to Oscillatoria. Microcystis and
Anabaena - May also be linked to Aphanizomenon
- 1,289,000 pounds of fish affected in August 2000
- Copper sulfate cannot be utilized in all ponds
3
Approach
- Modify chemical, physical, or biological
environments to discourage blue-green algal
growth - Utilize herbicides to control blue-green algae
- Utilize plankton eating fish to control algal
populations
4
Commonly Used Treatments
- Copper sulfate
- Copper liquid formulations
- Diuron
- Shad stocked to eat algae
5
Copper Algicides
- Only algicides registered for legal use
- Not consistent in control of problem algae
- Not selective to problem algae
- Little margin of safety to fish
- Can only be used with alkalinity above 50 ppm
- 0.1 ppm to 0.25 ppm may control for a short time
6
Copper Liquid Formulations
- Use label recommendations
- Some can be used at low alkalinities
- Chelates and EarthTech
- Effects do not last very long
7
Shad Stocking
- 1,000 per surface acre
- Stock early in the Spring or in late Winter
- May delay the dominance of Blue-greens until
August or later - May shift algal populations toward a diverse
community of 20 or more species
8
Plankton Feeding Fish
- Shad select for phytoplankton
- Fathead minnows are omnivorous but consume algae
- U. Georgia, Auburn U., Louisiana State U. are
involved in this regional project
9
Fish Stocking Densities
- Shad of about 1,000 per acre should produce about
200 to 400 pounds per acre - Stock shad in early spring to allow spawn
- Fathead minnows at 2,000 per acre, use spawning
structure - Catfish at 7,500 to 10,000 per acre
10
Shad Results - Bluegreen Numbers (x 1,000,000/L)
11
Catfish Only - Bluegreen Numbers (x 1,000,000/L)
12
Minnows Stocking- Bluegreen Numbers (x1,000,000/L)
13
Algal Control Evidence
- Shad ponds have smaller numbers of Blue-greens
and fewer off-flavor species - Ponds were also stocked with 7,000 catfish per
acre and fed up to 160 lb/A/day - Algal scums were visible in some shad ponds
- Off-flavor was absent in ponds with shad
14
Industry Trends
- Copper use will continue, sometimes rotated with
Diuron - Diuron rate now about 1/2 oz per surface acre
down from 1/2 oz per acre-ft - Shad will be stocked where they are available
- Off-flavor still occurs, but with lower frequency
15
Label Extension Proceedure
- Collect data to justify need for label extension
- Complete Section-18 application
- Obtain clearance for submission by GA Department
of Agriculture - Obtain permission for extension by Griffin Corp.
- GA Dept Ag applies to US EPA
16
Algae Species in Off Flavor Ponds
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