Seasonal variation in nutrient content of kelp


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This is a presentation at the Abalone Farmers Assosiation of Southern Africa project meeting in 2004. It details the progress we made from 2002 - 2004 on using kelps as a feed source for abalone.

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Seasonal variation in nutrient content of kelp

  1. 1. Seasonal variation in nutrient content of kelp AFASA project meeting 2004 <ul><li>D. V. Robertson-Andersson </li></ul>
  2. 2. Seasonal variation in nutrient content of kelp What do we know? <ul><li>Distribution of kelp is largely dependant on nutrient concentrations (NO 3 and PO 4 ). </li></ul><ul><li>There is a difference in kelp bed ecology on west and south coasts </li></ul><ul><li>Kelps obtain all their nutrient and mineral requirement from the water, through the fronds and stipe </li></ul><ul><li>No studies have looked at seasonal variation in nutrient or phenol content </li></ul>
  3. 3. Why is it important? <ul><li>Abalone are herbivores </li></ul><ul><li>They obtain all of their protein requirement from their diet </li></ul><ul><li>Their FCR is affected by phenols (an anti-grazer deterrent produced by most seaweeds) </li></ul><ul><li>Kelps can contain very high proportions of phenols </li></ul><ul><li>Abalone obtain all their calcium requirement through their gills, but no phosphate </li></ul><ul><li>The phosphate requirement has to be met by the diet </li></ul><ul><li>Abalone are sold by weight and there can be up to a 30% water loss during transport </li></ul>
  4. 4. West Coast
  5. 5. South Coast / Walker Bay area
  6. 6. Tissue Nitrogen vs. Tissue Phosphorus Tissue N vs. Tissue P of Ulva lactuca from west coast A S O N D J F M A M J J A
  7. 7. Moving forward <ul><li>Look at seasonal variations on a long term basis of Tissue N, P and phenol content </li></ul><ul><li>Do this from a variety of kelp beds </li></ul>
  8. 8. Moving forward <ul><li>How? </li></ul><ul><li>Each farm in an area can take 3 X 500g samples of kelp every two weeks </li></ul><ul><li>Freeze them immediately in labeled black bags until they can be analyzed </li></ul><ul><li>Analysis will occur in batches of not less than 50 </li></ul><ul><li>Data will be entered onto a data base and analyzed on a 6 monthly basis </li></ul>
  9. 9. Cost <ul><li>Materials? </li></ul><ul><li>Selenium tablets most expensive item R1, 00 </li></ul><ul><li>Other chemicals work out to 75 c a sample </li></ul>
  10. 10.   THE END Thank you ACKNOWLEDGEMENTS I would like to extend special thanks to the following people and organizations: 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