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 aquaculture effluent

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CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT

  1. 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. 2. Why cultivate seaweeds on abalone farms? <ul><li>Mixed diet gives better growth rates </li></ul><ul><li>MSY of kelp bed reached in 2002 </li></ul><ul><ul><li>Potential over-harvesting </li></ul></ul><ul><ul><li>Decrease in epiphyte densities </li></ul></ul><ul><li>Limited suitable coastal areas </li></ul><ul><li>‘ HAB’s’ </li></ul><ul><li>Recirculation </li></ul><ul><li>I ntegration will improve water quality </li></ul>
  3. 3. AIMS <ul><li>1) F easibility of growing commercially useful amounts of Gracilaria and Ulva </li></ul><ul><li>Influence of different growth media (seawater, abalone and turbot effluent water and fertilized seawater) on growth rates and yields. </li></ul><ul><li>Seasonal changes in tissue N and P content </li></ul><ul><li>Relationships between stocking density and yield </li></ul><ul><li>Uptake rates of various nutrients at differing stocking densities </li></ul>
  4. 4. PROJECT SITES <ul><li>A balone mariculture farms </li></ul><ul><li>Danger Point (I & J Mariculture Farm) + 140 km east of CT </li></ul><ul><li>Jacobs Baai (Jacobs Baai Sea Products) + 120 km N of CT </li></ul>
  5. 5. PROJECT DESIGN AT I & J <ul><li>12 Ulva tanks (5 X 1 X 0.63 m) & 12 Gracilaria tanks </li></ul><ul><li>Run as a commercial operation </li></ul><ul><li>+ 4 volume exchanges per day (later changed to 12) </li></ul><ul><ul><li>8 filtered seawater tanks </li></ul></ul><ul><ul><li>8 pulse fertilized sea water tanks </li></ul></ul><ul><ul><li>8 abalone effluent tanks </li></ul></ul>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. 6. Longitudinal profile of tanks Transverse profile of tanks 5 m 1 m
  7. 7. PROJECT DESIGN AT JSP <ul><li>20 Ulva tanks (100 L) & 20 Gracilaria tanks </li></ul><ul><li>Run as a experimental operation </li></ul><ul><li>+ 20 volume exchanges per day </li></ul><ul><ul><li>8 filtered seawater tanks (control) 4 small and 4 medium </li></ul></ul><ul><ul><li>6 turbot effluent tanks </li></ul></ul><ul><ul><li>6 abalone effluent tanks </li></ul></ul>1 2 3 4 1 2 3 4 1 2 3 4 Sea water Turbot effluent Abalone effluent 20 20 20
  8. 8. Small tanks Medium tanks 0.5 m 1 m 1 m 1 m
  9. 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. 10. RESULTS RGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
  11. 11. RESULTS SGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
  12. 12. RESULTS SGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
  13. 13. RESULTS Myrionema strangulans (MS) <ul><li>Brown spots </li></ul><ul><li>Numbering between 5 and 10 on the holdfast section of Ulva thalli </li></ul><ul><li>The spots are regular discs, 1 – 3 mm in diameter </li></ul><ul><li>First record for South Africa </li></ul><ul><li>Identified by Dr. Herre Stegenga </li></ul><ul><li>Negative correlation between infection density and SGR </li></ul>
  14. 14. RESULTS Myrionema strangulans (MS) BAD INFECTION DEAD HEALTHY INFECTED
  15. 15. RESULTS MS infestation of Ulva thalli
  16. 16. RESULTS <ul><li>In Quasi-commercial system using 10 tanks: </li></ul><ul><li>Summer 291 kg. wwt.m -2 .d -1 </li></ul><ul><li>Winter 135 kg. wwt.m -2 .d -1 </li></ul><ul><ul><li>Increase by using fertilizer and Kelpak® in effluent media at 12 volume exchanges per day </li></ul></ul><ul><li>RESULT </li></ul><ul><li>Summer 740 kg. wwt.m -2 .d -1 </li></ul><ul><li>Winter 234 kg. wwt.m -2 .d -1 </li></ul>YIELDS
  17. 17. RESULTS <ul><li>Are important because: </li></ul><ul><li>Low water exchange rate leads to: </li></ul><ul><ul><li>Carbon and nutrient limitation </li></ul></ul><ul><ul><li>Poor condition of thalli (bleached & broken) </li></ul></ul><ul><ul><li>Low Nitrogen content </li></ul></ul><ul><ul><li>Low SGR </li></ul></ul><ul><li>therefore low yield </li></ul><ul><li>Measures </li></ul><ul><li>Carbon limitation in seaweeds can be shown by an increase in pH values </li></ul>FLOW RATES (4, 12 & 20)
  18. 18. RESULTS SHADING <ul><li>Shading helps to reduce epiphytes </li></ul><ul><li>Helps in decreasing MS infestations </li></ul><ul><li>Helps to increase tissue N and P </li></ul><ul><li>Tanks should be shaded from September to January </li></ul><ul><li>Shade cloth must be 20 % not 50 % </li></ul>
  19. 19. RESULTS <ul><li>Important because: </li></ul><ul><li>Increases protein from wild harvest (3.7- 24 % wild to 49.8 % cultured) </li></ul><ul><li>Abalone receive more protein </li></ul><ul><li>Faster growth rates </li></ul><ul><li>How do you increase tissue nutrients? </li></ul><ul><li>Faster flow rates (12 – 20 volume exchanges) </li></ul><ul><li>Grown in turbot/fish or abalone effluent </li></ul><ul><li>Add Fertilizer and Kelpak® </li></ul>Tissue Nitrogen
  20. 20. RESULTS Tissue Nitrogen vs. Thallus Colour Tissue nitrogen vs. thallus colour
  21. 21. RESULTS <ul><li>Ulva can take up 90 % of ammonium in abalone effluent at 12 volume exchanges per day </li></ul><ul><li>DO values don’t go below 9 mg.l -1 at night </li></ul><ul><li>Using stocking density of 3 kg. wwt.m -2 gives best uptake rates but is system specific </li></ul><ul><li>Toxic ammonia never reaches levels harmful to abalone at above stocking density </li></ul>RECIRCULATION
  22. 22. Results ECONOMICS
  23. 23. RESULTS ECONOMICS Abalone growth curves
  24. 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. 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. 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. 27. CONCLUSIONS <ul><li>This study has shown that it is possible to grow Ulva in abalone effluent and that it has economic benefits as well </li></ul><ul><li>Yields lower than those reported in literature by 3 - 5 % day-1, but smaller tanks were used in those studies </li></ul><ul><li>It is possible to increase yields by using a pulse fertilization, Kelpak® and effluent water as the culture medium </li></ul><ul><li>By growing a combination of Ulva and Gracilaria you can account for seasonal growth in seaweeds and maintain a constant yield </li></ul>
  28. 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

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