Avni Melech

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TILAPIA PRODUCTION INBIOFLOC SYSTEMS

YORAM AVNIMELECH

TECNION, ISRAEL INST. Of TECHNOLOGY

[email protected]


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Tilapia production, a growing industry

Tilapia is becoming a very popular fishand its production an important

aquacultureindustry


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Tilapia, an ideal fish for Biofloc Technology

Grow well in denseculturesResistant

FILTER FEEDERVery few studies as

compared withshrimp


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Fish BiomassNormally, 20-30 kg/m210 times higher than shrimp BFT ponds!


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Implications:

z High Biomass 20-30 kg/m3z High feeding (ca 500 g feed/m3 per day!)

z Very high microbial activity

z High floc volume (20-50 ml/l).z Very high natural feed storage.

z High levels of feed residues

z Need to drain out daily (or twice daily) excessivesludge.

z Pond constructed to facilitate sludge draining

and perfect mixing.z High and effective aeration: 10-20 hp/1000 m2

ond


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Drain bottom sludge twice daily till youget clear water


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Bioflocs and Floc volume

z Bio flocs are made of bacteria, protozoa,feed residues etc.

z Bioflocs size may reachA few mm diameter

z Effectively harvested

by tilapia


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x20x10

x10 x10

200 m

200 m 200 m

Flo

Bio f loc s are m ade o f bac t er ia ,

prot ozoa, e t c . Typic a l y t he ir d iam et er is 0.1-2 m m .


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Protein Recycling

z Normally, fish or shrimp recover just ~25% offeed protein.

z

In bacterial controlled ponds, they eat theprotein twice; Once in the feed and then theyconsume microbial protein. The protein

recovery reaches almost 50%.

z Protein is the most expensive part of the feed.


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BFTcontrol. # 1Expt51 days

16.611.1FEED C/N

2.0b1.59aDaily Gain (%)

2.172.62FCR

2.424.38PCR

0.5830.848FEED COST)US$/Kg fish(Exp. # 2 (30 days)

16.611.1C/N

2.22b1.63a

Daily gain (%)2.022.62FCR

2.184.35PCR

0.5430.848

Feed cost(US$/Kg fish)


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Preparing an 15N tagged bioflocs:

z 1. Prepare large enough batch of bioflocsuspension (water + feed, mix & aerate).

z 2. Add15

N salt.z 3. Add starch, at a C/N ratio of > 15

z 4. After a few hours, practically all 15N is inthe bioflocs.


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Results 1: %15

N in fish

% 15 N in fish

0.3000

0.3500

0.4000

0.4500

0.5000

0.5500

1 3 5 7 9 11 13 15

Days

%15N


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Residence time of bioflocs

z Bioflocs were taken up by fish and degradedbiologically. Yet, the amount of bioflocsstayed almost constant. This implies that new

flocs are constantly produced (using theexcreted N).

z The residence time of bioflocs wascalculated to be around 8 hours. The flocsseem to be a very dynamic system.

z most cells in the flocs are young and active.


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Data on feed protein utilization

z Conventional fish, shrimp ponds 20-25%

z BFT Tilapia ponds (Avnimelech) 45%

z BFT Shrimp ponds (McIntosh) 45%

z Closed shrimp tanks (Velasco) 63%

z BFT shrimp ponds,15

N study 18-29% of total Nconsumption (Michele Burford et al.)

* Tilapia, 15N Study, flocs supplied about 50% of

fish protein requirement. (Avnimelech).


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Feed Utilization

z Fish or shrimp growing in BFT systemseat the pellets when applied, but eatbioflocs all the time.

z Confirmed in a work done by Albert Taconwith shrimp.

z

Observations with tilapia.z Effects on lowering of FCR in tilapia

production


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Fresh results from the field:

z Tilapia fingerlings (120 g) stocked to over-wintering facility on January 4, 2011.

z Feeding ~ 1% BWz On February 18, they weighed 171 g

z Daily growth of 1.16 g/fish

z FCR = 0.5


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OVER-WINTERING


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Results

zTemperature and oxygen control

Dissolved oxygen: 9 10 mg O2/L

Average temperature: 18 2C


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AND SECONDARY INFECTION OF FISH BY STREPTOCOCCUSTotal infectedSick fishDead fishTreatment

a)Injected

fish

112 (2)9 (9)Control

164 (2)12 (3)BFT

a)Non-

injected

fish

11 (4.7)4 (1.5)7 (5)Highexchange

3 (1.4)1.3 (1.0)1.8(1.7)

ASP

High water exchange = 0.5l/min per kg fish (700% per day)

BFT< Limited water exchange = 10% per day

Control

BFT

EFFECT OF WATER EXCHANGE RATE ON PRIMARY

Control

BFT


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Conclusions

z Biofloc technology is especially adapted to raisetilapia production up to 20-30 kg/m2.

z This can be done using not too expensive system.

z BFT enables feed recycling, high feed quality andreduced expenses.

z BFT reduces disease.

z The system is friendly and forgiving.

z More research is needed


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Thank You

Yoram

Avni Melech

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