Docstoc

off-flavor

Document Sample
off-flavor Powered By Docstoc
					Off-flavor Management

          Gary Burtle
     Animal & Dairy Science
      University of Georgia
         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
                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
     Commonly Used Treatments
•   Copper sulfate
•   Copper liquid formulations
•   Diuron
•   Shad stocked to eat algae
          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
     Copper Liquid Formulations
•   Use label recommendations
•   Some can be used at low alkalinities
•   Chelates and EarthTech
•   Effects do not last very long
             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
       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
      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
     Shad Results - Bluegreen
     Numbers (x 1,000,000/L)
35

30

25

20                                             Pond 14
15                                             Pond 17
                                               Pond 22
10

 5

 0
     Jan   Mar   Apr   May   Jun   Jul   Aug
      Catfish Only - Bluegreen
      Numbers (x 1,000,000/L)
100
 90
 80
 70
 60
                                                Pond 13
 50
                                                Pond 15
 40                                             Pond 21
 30
 20
 10
  0
      Jan   Mar   Apr   May   Jun   Jul   Aug
Minnows Stocking- Bluegreen
  Numbers (x1,000,000/L)
80
70
60
50
                                               Pond 16
40
                                               Pond 20
30                                             Pond 23
20
10
0
     Jan   Mar   Apr   May   Jun   Jul   Aug
      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
            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
   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
     Algae Species in Off Flavor
               Ponds
10
 9
 8
 7                                          Microcystis
 6                                          Anabaena
 5                                          Oscillatoria
 4                                          Aphanizomenon
 3                                          Aphanocapsa
 2                                          Lyngbea
 1
 0
      1-1000   1001-2000 201-5000   5000+

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:7
posted:9/17/2012
language:Unknown
pages:16