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PILOT, COMMERCIAL SCALE, CULTIVATION OF ULVA AND GRACILARIA ON AN ABALONE FARM AT DANGER POINT (CAPE SOUTH COAST)
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PILOT, COMMERCIAL SCALE, CULTIVATION OF ULVA AND GRACILARIA ON AN ABALONE FARM AT DANGER POINT (CAPE SOUTH COAST)

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This was the first report back meeting at the Abalone Farmers Association of Southern Africa in 2002 and illustrated how we were going to cultivate Ulva and Gracilaria in Aquaculture effluent.

This was the first report back meeting at the Abalone Farmers Association of Southern Africa in 2002 and illustrated how we were going to cultivate Ulva and Gracilaria in Aquaculture effluent.

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  • 1. Robertson-Andersson, D. V .; Njobeni, A.; Bolton, J. J.; Anderson, R. J. & Probyn, T. A. PILOT, COMMERCIAL SCALE, CULTIVATION OF ULVA AND GRACILARIA ON AN ABALONE FARM AT DANGER POINT (CAPE SOUTH COAST)
  • 2. INTRODUCTION
    • S upplying abalone with a mixed diet gives better growth rates than do single-species diets
    • Potential over- harvesting of natural kelp beds
    • Limited suitable coastal areas
    • S.A. abalone farms are threatened by ‘ HAB’s’
    • I ncorporation of seaweeds into farm effluent system will improve water quality by reducing nutrient levels
  • 3. AIMS
    • 1) To assess the feasibility of growing commercially useful amounts of Gracilaria and Ulva
    • The influence of different growth media (seawater, abalone effluent water and fertilized seawater) on growth rates and yields.
  • 4. PROJECT SITE
    • A balone mariculture farm
    • Danger Point (I & J Mariculture Farm) + 140 km east of CT
  • 5. PROJECT DESIGN
    • 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 fresh 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
  • 7. PROJECT DESIGN
    • T anks supplied with air from a blower for the tumble culture
    • Ulva initially collected from Simons Town
    • Hoped to be a vegetative free-floating form of U. lactuca
    • Gracilaria collected from Saldanha Bay
    • Stocking density 2 kg m -2 of surface area
  • 8. METHODS
    • Harvesting
    • Monthly
    • Tanks are scrubbed to remove fouling algae
    • Tanks harvested, weighed, then restocked
    • Samples were taken to record dry to wet weight and for biochemical analysis
    • Growth Rate Experiments
    • Relative Growth rate (RGR = % d -1 )
    • RGR = [ln(W t / W 0 )] / (t t – t 0 )
    • The yield (Y = kg wwt m -2 d -1 )
    • Y = [(W t – W 0 ) / t] / SA
  • 9. RGR % day -1 J J A S O N D J F M A M J J A RESULTS RGR of Ulva from June ‘01 to Aug ‘02 in sea. (1) Indicates where shading started, (2) where water exchanges increased and (3) indicates where shading stopped. 1 3 2
  • 10. RGR % day -1 S O N D J F M A M J J A RESULTS RGR of Ulva from June ‘01 to Aug ‘02 in sea, fertilized & abalone effluent water. (1) Indicates where shading started, (2) where water exchanges increased and (3) indicates where shading stopped. 1 3 2
  • 11. RGR % day -1 J F M A M J RESULTS RGR of Ulva from June ‘01 to Jun ‘02 in sea, shaded sea, fertilized & abalone effluent water. (2) Indicates where water exchanges increased. 2
  • 12. 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
  • 13. RESULTS Myrionema strangulans (MS) BAD INFECTION DEAD HEALTHY INFECTED
  • 14. RESULTS RGR of Gracilaria from June ‘01 to April ’02 in Sea, fertilized & abalone effluent water. (1) Indicates where shading started (2) indicates where volume exchanges changed from 4 to 12. J J A S O N D J F M A 2 RGR % Day -1 1
  • 15. RESULTS
    • Reasons for low RGR in summer:
    • Low water exchange rate
    • Poor condition of thalli (bleached & broken)
      • Algae are either nutrient or carbon limited
        • An indication of Carbon limitation can be shown by an increase in pH values
  • 16. RESULTS pH values for Ulva at 4 V exchanges day -1 8 10 12 14 16 / 9 11 13 15 17 19 21 23 /1 3 5 7 8 12 16 20 Cool Day Pulse fertilization Hot Day
  • 17. CONCLUSIONS
    • Low water exchange rates are causing low RGR due to carbon limitation
    • Shown by increase in pH in slow flow tanks
      • Bleaching of thalli
      • Low RGR in summer
      • Further damage is caused by high temperatures in tanks and by high UV exposure
        • Which in the case of Ulva leads to MS infestations
  • 18. CONCLUSIONS
    • RGR is light and not temperature dependant
    • Using a pulse fertilization and effluent water is the best culture medium
    • Tanks should be shaded from September to January
    • Shade cloth must be 20 % not 50 %
    • Yields lower than those reported in literature by 3 - 5 % day -1 , but smaller tanks were used in those studies
    • By growing a combination of Ulva and Gracilaria you can account for seasonal growth in seaweeds and maintain a constant yield
  • 19.   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 N R F Swedish and South African Collaborative Programme
  • 20. PO 4 values for abalone incoming and out going water in shaded and unshaded tanks of Ulva . Area between red lines is range for seawater. RESULTS µ M PO 4 / L
  • 21. PO 4 values for Fertilized incoming and out going water in shaded and unshaded tanks of Ulva . Area between red lines is range for seawater. RESULTS µ M PO 4 / L

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