1. TILAPIA PRODUCTION IN BIOFLOC SYSTEMS
YORAM AVNIMELECH
TECNION, ISRAEL INST. Of TECHNOLOGY

2. Biofloc technology is based upon a few principles:
(a) Zero or minimal water exchange,
(b) subsequent development of dense microbial population
(c) managing the microbial population as a part of the pond eco-system
(d) adjustment of the C/N ratio to 15 in order to control inorganic nitrogen concentration in the water.
The bacteria, forming bioflocs, assimilate TAN, produce microbial proteins that is consumed by the fish, thus recycle the unused feed protein. (For more details: Yoram Avnimelech, Biofloc Technology, A Practical Handbook, World Aquaculture Soc. 2012).

4. Tilapia, an ideal fish for Biofloc Technology
Grow well in dense cultures
Resistant
FILTER FEEDER
Very few studies as compared with shrimp

5. Fish Biomass Normally, 20-30 kg/m2
10 times higher than shrimp BFT ponds!

6. Implications: High Biomass 20-30 kg/m3 (Up to more than 40kg/m3
(w/o O2)
High feeding (ca 500 g feed/m3 per day)
Very high microbial activity
High floc volume (20-50 ml/l).
Very high natural feed storage.
High levels of feed residues
Need to drain out daily (or twice daily) excessive sludge.
Pond constructed to facilitate sludge draining and perfect mixing.
High and effective aeration: hp/1000 m2 pond
Implications:

7. Drain bottom sludge twice daily till you get clear water

9. Bio flocs are made of bacteria, protozoa, feed residues etc.
Bioflocs size may reach
A few mm diameter
Effectively harvested
by tilapia

11. 200 µm
x10
x20
200 µm
200 µm
x10
x10
Bio flocs are made of bacteria, protozoa, etc. Typicaly their diameter is mm.

12. Protein Recycling Protein is the most expensive part of the feed.
Normally, fish or shrimp recover just ~25% of feed protein.
In bacterial controlled ponds, they eat the protein twice; Once in the feed and then they consume microbial protein. The protein recovery reaches almost 50%.
Protein is the most expensive part of the feed.
Protein Recycling

13. FEED COST (US$/Kg fish)
BFT
control
Expt. # 1
51 days
16.6
11.1
FEED C/N
2.0b
1.59a
Daily Gain (%)
2.17
2.62
FCR
2.42
4.38
PCR
0.583
0.848
FEED COST (US$/Kg fish)
Exp. # 2 (30 days)
16.6
11.1
C/N
2.22b
1.63a
Daily gain (%)
2.02
2.62
FCR
2.18
4.35
PCR
0.543
0.848
Feed cost
(US$/Kg fish)

14. Results 1: % 15N in fish

15. Residence time of bioflocs
Bioflocs were taken up by fish and degraded biologically. Yet, the amount of bioflocs stayed almost constant. This implies that new flocs are constantly produced (using the excreted N).
The residence time of bioflocs was calculated to be around 8 hours. The flocs seem to be a very dynamic system.
most cells in the flocs are young and active.
Residence time of bioflocs

16. Data on feed protein utilization
Conventional fish, shrimp ponds %
BFT Tilapia ponds (Avnimelech) %
BFT Shrimp ponds (McIntosh) %
Closed shrimp tanks (Velasco) %
BFT shrimp ponds, 15N study 18-29% of total N consumption (Michele Burford et al.)
* Tilapia, 15N Study, flocs supplied about 50% of fish protein requirement. (Avnimelech).
Data on feed protein utilization

17. Fish or shrimp growing in BFT systems eat the pellets when applied, but eat bioflocs all the time.
Confirmed in a work done by Albert Tacon with shrimp.
Observations with tilapia.
Effects on lowering of FCR in tilapia production
Feed Utilization

19. SPECIAL USES, ADDED VALUES
DESERT AQUACULTURE

20. Effects on propagation
Shrimp broodstock grown in BFT have earlier sexual maturity
And higher productivity
Similar result with tilapia
Work by Julie Ekasari
Better nutrition? Fatty acids?
Hormonal effects?

21. Summary of fatty acids analysis on the collected bioflocs
% Total Fatty Acids
Total n-3
1.33
Total n-6
19.70
Total n-9
12.97 LA
13.43
ALA
0.36
EPA
0.56
DHA
0.32 AA
1.30
n-6 fatty acids is essential for tilapia and its reproduction (Watanabe 1982)
Protein : 37 – 46% DW
Lipid : 11.9 % DW
Protein content of bioflocs collected from the BFT tank was ranged from 37 to 46%, whereas lipid level was around 11%.
Fatty acids analysis of the bioflocs on day 84 showed that this bioflocs was rich in n-6 fatty acids which is considered as essential fatty acids for tilapia (Watanabe 1982).
Previous studies showed that tilapia provided with diets containing vegetable oil rich in n-6 (soybean oil and CPO) resulted in higher reproductive performance than that of fish oil (Watanabe 1982; Ng & Wang 2011).
It is also important to note that this bioflocs contained considerably high concentration of arachidonic acid (AA) which is a highly unsaturated fatty acids which plays an important role in fish fertilization success by stimulating testicular testosterone in goldfish (Izquierdo et al 2001)
Biofloc considerably high in AA (Arachidonic Acid)
AA is beneficial for fertilization rates  stimulates testicular testosterone in goldfish (Izquierdo et al 2001)

22. What triggers the fish to spawn? (Rocha 2008)
2. Physiological factors
Hormones
Morphological changes
Mobilization of energy reserves
Blood total cholesterol in fish in BFT tanks was higher
Cholesterol  precursor of steroids hormones
Blood glucose as an indicator of mobilization of energy reserves
Fish growth
The second factor which affect the reproductive efficiency in fish is physiological factor which include hormones, morphological changes and mobilization of energy reserves.
In the present study, we measured blood total cholesterol and glucose concentration as the indicator for physiological factors related to reproductive activity.
Cholesterol is known as a precursor for the biosynthesis of steroid hormones, including those which function in reproduction such as testosterone, estrogens, and progestogens (Lubzens, Young, Bobe & Cerda, 2010), whereas blood glucose can be used as an indicator of energy reserves mobilization during reproductive period.

23. Results: Blood total cholesterol
Higher concentration in BFT  higher concentration of hormones were involved?
It is shown in this graph that blood cholesterol levels of the fish in BFT tanks were consistently higher than those in the Control tanks.
Higher levels of blood cholesterol in BFT treatment can be supportive to improved reproductive performance of broodfish in this treatment.
The higher concentration might also indicate that there might be higher concentration of reproductive hormones were involved which eventually resulted in a better reproductive performance of the fish in BFT?.
This we believe can be interesting to be further investigated.
Low total cholesterol level in the blood (less than 180 mg.dL-1) compared to a previous study (Chen et al 2003) could be associated with the fact that the fish had been undergoing spawning activities (McDonald & Milligan, 1992).

24. Results: Blood glucose
Higher concentration in BFT 
More energy was mobilized for reproductive activities
More energy supply?
Blood glucose levels in the fish in BFT treatment were also found to be constantly higher than those of the control, and the difference were significant, specifically on day 42 and 56.
Blood glucose values may designate higher energy mobilization and also energy supply for the fish in BFT tanks during their reproductive period.

25. Results: Average body weight
Despite of more active reproductive performance the female in BFT tanks grew better
Yet, the fish in BFT required less feed
(9.3 vs 8.3 kg/tank)
The fish average body weight during the experimentation showed that despite of the higher reproductive performance, the fish in BFT tanks still grew better than those in the control tanks, and yet they consumed significantly less feed.

26. Results : Total fish fry productionb
Total fish fry production per tank after 84 days of experimental periods in BFT treatment was 65% higher than that of the control and significant at P<0.05
Julie Eskari

27. Fresh results from the field:
Tilapia fingerlings (120 g) stocked to over-wintering facility on January 4, 2011.
Feeding ~ 1% BW
On February 18, they weighed 171 g
Daily growth of 1.16 g/fish
FCR = 0.5
Fresh results from the field:

28. OVER-WINTERING

30. 11 (4.7) EFFECT OF WATER EXCHANGE RATE ON PRIMARY Injected fish
AND SECONDARY INFECTION OF FISH BY STREPTOCOCCUS
Total infected
Sick fish
Dead fish
Treatment 11
2 (2)
9 (9)
Control 16
4 (2)
12 (3)
BFT
Control
Injected fish
BFT
(4.7)
(1.5)
(5)
High exchange
3 (1.4)
1.3 (1.0)
(1.7)
ASP
Non-injected fish
Control
BFT
High water exchange = 0.5l/min per kg fish (700% per day)
BFT< Limited water exchange = 10% per day

31. Luo and coworkers in China reported
Yields of 45kg/m3. Higher production and
lower FCR as compared with RAS.
Higher concentrations of Superoxide
Permutase .

32. Conclusions
Biofloc technology is especially adapted to raise tilapia production up to kg/m2.
This can be done using not too expensive system.
BFT enables feed recycling, high feed quality and reduced expenses.
BFT reduces disease.
The system is friendly and forgiving.
More research is needed

33. Cultivo de tilapia en sistemas biofloc es simple, fácil y rentable
Cultivo de tilapia en sistemas biofloc es simple, fácil y rentable. • Tilapia como filtrador es feliz en esos sistemas. • Se ahorra los gastos de alimentación (~ 30%) y comer mejor. • Menos enfermedades. • Mayor crecimiento y menor FCR. • La manera más rápida de iniciar la producción intensiva de tilapia. • Si necesita ayuda, estaré feliz de hacerlo: