CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT
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CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT

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This is a presentation at the Abalone Farmers Assosiation of Southern Africa project meeting in 2003. It details the progress we made from 2000 - 2002 on using seaweeds as biofilters in......

This is a presentation at the Abalone Farmers Assosiation of Southern Africa project meeting in 2003. It details the progress we made from 2000 - 2002 on using seaweeds as biofilters in aquaculture effluent

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  • 1. Robertson-Andersson, D. V .; Bolton, J. B.; Anderson, R. J. & Probyn, T. A. CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT AFASA project meeting 2003
  • 2. Why cultivate seaweeds on abalone farms?
    • Mixed diet gives better growth rates
    • MSY of kelp bed reached in 2002
      • Potential over-harvesting
      • Decrease in epiphyte densities
    • Limited suitable coastal areas
    • ‘ HAB’s’
    • Recirculation
    • I ntegration will improve water quality
  • 3. AIMS
    • 1) F easibility of growing commercially useful amounts of Gracilaria and Ulva
    • Influence of different growth media (seawater, abalone and turbot effluent water and fertilized seawater) on growth rates and yields.
    • Seasonal changes in tissue N and P content
    • Relationships between stocking density and yield
    • Uptake rates of various nutrients at differing stocking densities
  • 4. PROJECT SITES
    • A balone mariculture farms
    • Danger Point (I & J Mariculture Farm) + 140 km east of CT
    • Jacobs Baai (Jacobs Baai Sea Products) + 120 km N of CT
  • 5. PROJECT DESIGN AT I & J
    • 12 Ulva tanks (5 X 1 X 0.63 m) & 12 Gracilaria tanks
    • Run as a commercial operation
    • + 4 volume exchanges per day (later changed to 12)
      • 8 filtered seawater tanks
      • 8 pulse fertilized sea water tanks
      • 8 abalone effluent tanks
    1 2 3 4 1 2 3 4 1 2 3 4 Sea water Fertilized sea water Abalone waste water 4 V 4 V 12 V 12 V 12 V 12 V
  • 6. Longitudinal profile of tanks Transverse profile of tanks 5 m 1 m
  • 7. PROJECT DESIGN AT JSP
    • 20 Ulva tanks (100 L) & 20 Gracilaria tanks
    • Run as a experimental operation
    • + 20 volume exchanges per day
      • 8 filtered seawater tanks (control) 4 small and 4 medium
      • 6 turbot effluent tanks
      • 6 abalone effluent tanks
    1 2 3 4 1 2 3 4 1 2 3 4 Sea water Turbot effluent Abalone effluent 20 20 20
  • 8. Small tanks Medium tanks 0.5 m 1 m 1 m 1 m
  • 9. 0 1 2 3 4 5 6 7 8 sea shaded sea fert shaded fert abalone shaded abalone SGR % day -1 J J A S O N D J F M A M J J A S O RESULTS SGR of Ulva from June ‘01 to October ‘02 in sea, fertilized & abalone effluent water. (2) where water exchanges increased at I & J 2
  • 10. RESULTS RGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
  • 11. RESULTS SGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
  • 12. RESULTS SGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
  • 13. RESULTS Myrionema strangulans (MS)
    • Brown spots
    • Numbering between 5 and 10 on the holdfast section of Ulva thalli
    • The spots are regular discs, 1 – 3 mm in diameter
    • First record for South Africa
    • Identified by Dr. Herre Stegenga
    • Negative correlation between infection density and SGR
  • 14. RESULTS Myrionema strangulans (MS) BAD INFECTION DEAD HEALTHY INFECTED
  • 15. RESULTS MS infestation of Ulva thalli
  • 16. RESULTS
    • In Quasi-commercial system using 10 tanks:
    • Summer 291 kg. wwt.m -2 .d -1
    • Winter 135 kg. wwt.m -2 .d -1
      • Increase by using fertilizer and Kelpak® in effluent media at 12 volume exchanges per day
    • RESULT
    • Summer 740 kg. wwt.m -2 .d -1
    • Winter 234 kg. wwt.m -2 .d -1
    YIELDS
  • 17. RESULTS
    • Are important because:
    • Low water exchange rate leads to:
      • Carbon and nutrient limitation
      • Poor condition of thalli (bleached & broken)
      • Low Nitrogen content
      • Low SGR
    • therefore low yield
    • Measures
    • Carbon limitation in seaweeds can be shown by an increase in pH values
    FLOW RATES (4, 12 & 20)
  • 18. RESULTS SHADING
    • Shading helps to reduce epiphytes
    • Helps in decreasing MS infestations
    • Helps to increase tissue N and P
    • Tanks should be shaded from September to January
    • Shade cloth must be 20 % not 50 %
  • 19. RESULTS
    • Important because:
    • Increases protein from wild harvest (3.7- 24 % wild to 49.8 % cultured)
    • Abalone receive more protein
    • Faster growth rates
    • How do you increase tissue nutrients?
    • Faster flow rates (12 – 20 volume exchanges)
    • Grown in turbot/fish or abalone effluent
    • Add Fertilizer and Kelpak®
    Tissue Nitrogen
  • 20. RESULTS Tissue Nitrogen vs. Thallus Colour Tissue nitrogen vs. thallus colour
  • 21. RESULTS
    • Ulva can take up 90 % of ammonium in abalone effluent at 12 volume exchanges per day
    • DO values don’t go below 9 mg.l -1 at night
    • Using stocking density of 3 kg. wwt.m -2 gives best uptake rates but is system specific
    • Toxic ammonia never reaches levels harmful to abalone at above stocking density
    RECIRCULATION
  • 22. Results ECONOMICS
  • 23. RESULTS ECONOMICS Abalone growth curves
  • 24. RESULTS 31.2 % increase in weight using rotation diet vs kelp only diet over 9 months Cost: $30 per kg X R 8 = R 240 10 (100g) abalone in 1 kg cost per abalone = R 24 less profit and freight = R 15 per abalone ECONOMICS
  • 25. RESULTS Increase in SGR: 49 – 68 % per year Normal Growth to 100g = 5 years accelerated growth = 3.3 – 3.6 years @ R 15 per abalone New cost : R 12.40 – R 13.50 per abalone Savings: 17 – 28 % R 1.50 - R 2.60 per abalone ECONOMICS
  • 26. RESULTS Average farm (50 tons @ 100 g per abalone) = 500 000 100g abalone X R 1.50 or R 2.60 EQUALS Savings: R 800 000 – R 1.3 million ECONOMICS
  • 27. CONCLUSIONS
    • This study has shown that it is possible to grow Ulva in abalone effluent and that it has economic benefits as well
    • Yields lower than those reported in literature by 3 - 5 % day-1, but smaller tanks were used in those studies
    • It is possible to increase yields by using a pulse fertilization, Kelpak® and effluent water as the culture medium
    • By growing a combination of Ulva and Gracilaria you can account for seasonal growth in seaweeds and maintain a constant yield
  • 28.   THE END Thank you ACKNOWLEDGEMENTS I would like to extend special thanks to the following people and organizations without whose help this project would be impossible: I & J Mariculture farm particularly N. Loubser, H. Otto and L. Ansara JSP Mariculture farm particularly K. Ruck N R F Swedish and South African Collaborative Programme