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