CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT
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Transcript of CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT
Robertson-Andersson, D. V.; Bolton, J. B.; Anderson, R. J. & Probyn, T. A.
CULTIVATION OF ULVA IN AQUACULTURE EFFLUENT
AFASA project meeting 2003
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
• Integration will improve water quality
AIMS
1) Feasibility of growing commercially useful amounts of Gracilaria and Ulva
2) Influence of different growth media (seawater, abalone and turbot effluent water and fertilized seawater) on growth rates and yields.
3) Seasonal changes in tissue N and P content
4) Relationships between stocking density and yield
5) Uptake rates of various nutrients at differing stocking densities
PROJECT SITES
Abalone mariculture farms
• Danger Point (I & J Mariculture Farm) + 140 km east of CT
• Jacobs Baai (Jacobs Baai Sea Products) + 120 km N of CT
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 V12 V 12 V 12 V
Longitudinal profile of tanks
Transverse profile of tanks
5 m
1 m
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
Small tanks
Medium tanks
0.5 m
1 m
1 m
1 m
0
1
2
3
4
5
6
7
8
sea shaded sea fert
shaded fert abalone shaded abalone
SG
R %
day
-1
J J A S O N D J F M A M J J A S O
2
RESULTS
SGR of Ulva from June ‘01 to October ‘02 in sea, fertilized & abalone effluent water. (2) where water exchanges increased at I & J
RESULTS
RGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
0
2
4
6
8
10
12
14
28-Jul 16-Sep 5-Nov 25-Dec 13-Feb 4-Apr 24-May
13-Jul 1-Sep 21-Oct 10-Dec
SG
R (
%.d
)
Small sea Medium sea
RESULTS
SGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
0
2
4
6
8
10
12
14
28-Jul 16-Sep 5-Nov 25-Dec 13-Feb 4-Apr 24-May 13-Jul 1-Sep 21-Oct 10-Dec
SG
R (
%.d
)
Small sea Medium sea turbot
RESULTS
SGR of Ulva from June ‘01 to October ‘02 in sea, Turbot & abalone effluent water at JSP.
0
2
4
6
8
10
12
14
28-Jul 16-Sep 5-Nov 25-Dec 13-Feb 4-Apr 24-May 13-Jul 1-Sep 21-Oct 10-Dec
SG
R (
%.d
)
Small sea Medium sea turbot abalone
RESULTSMyrionema 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
BAD INFECTION
DEAD
RESULTSMyrionema strangulans (MS)
HEALTHY
INFECTED
RESULTS
MS infestation of Ulva thalli
y = -0.4557x + 3.2565
R2 = 0.2605
0
2
4
6
8
0 1 2 3 4 5 6
B-B scale of infection
SGR
(% D
ay)
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
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)
RESULTSSHADING
• 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 %
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
RESULTSTissue Nitrogen vs. Thallus Colour
Tissue nitrogen vs. thallus colour
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
ResultsECONOMICS
RESULTSECONOMICS
0
50
100
150
200
250
300
0 2 4 6 8 10 12 14 16
Years
Len
gth
(m
m)
Normal growth Accelerated growth @ 49% Accelerated growth @ 68 %
Abalone growth curves
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
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
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
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
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