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Prepared By; Gokhale Govinda Satish M.F.Sc (Aquaculture)

Introduction 

As the human population continues to grow, food production industries such as aquaculture will need to expand as well.

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Shrimp farming has become competitive and as such the technology utilized needs to be efficient in all aspects – productivity, quality, sustainability, bio-security and to be in line with market demand.

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In order to preserve the environment and the natural resources, this expansion will need to take place in a sustainable way.

Three Goals…. 

The prime goal of aquaculture expansion must be to produce more aquaculture products without significantly increasing the usage of the basic natural resources of water and land.

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The second goal is to develop sustainable aquaculture systems that will not damage the environment.

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The third goal is to build up systems providing an equitable cost/benefit ratio to support economic and social sustainability.

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All these three prerequisites for sustainable aquaculture development can be met by biofloc technology

Definition:The Biofloc is a protein rich macro aggregate of organic material and micro-organisms including diatoms, bacteria, protozoa, algae, fecal pellets, remains of dead organisms and other invertebrates.

Biofloc Technology Biofloc technology is a technique of enhancing water quality in aquaculture through balancing carbon and nitrogen in the system. 

The technology has recently gained attention as a sustainable method to control water quality, with the added value of producing protein rich feed in situ.

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The basic technology was developed by Dr. Yoram Avnimelech in Israel and initially implemented commercially in Belize by Belize Aquaculture.

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Biofloc technology has become a popular technology in the farming of Pacific white shrimp, Litopenaeus vannamei

Cont….. 

It is possible that this microbial protein has a higher availability than feed protein.

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The basic requirements for biofloc system operation include high stocking density, high aeration and lined ponds.

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A crucial factor in the system is the control of biofloc in ponds during operation. Fish /shrimp are fed with a lot of feed

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About 70-80% of it remains in the pond, in the water or the sediment.

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Ponds contain a high load of nutrients

The outcome…. What are the outcomes? -We waste Feed/Money (Quite a lot!) - Toxic residues (Sulphides, Ammonia etc) accumulate.

- Fish growth is affected. - Intensification is limited (loose income, not being able to raise production)

- Use industrial RAS (Recycling Aquaculture systems) Quite expensive ) - use biofloc technology.

Basic of BFT in Shrimp Farming 1. High stocking density - over 130 – 150 PL10/m2

2. 3. 4. 5. 6 7.

High aeration – 28 to 32 HP/ha/ PWAs Paddle wheel position in ponds HDPE / Concrete lined ponds Grain (pellet) Molasses Expected production 20–25 MT/ha/crop

High density

High aeration

Grain pellet

Bioflocs

Dark Vannamei

Paddle Wheels position

HDPE lined pond

Pond Operation High Aeration

Siphoning

STAGES FLOC Development stages (vol) in pond Stage 1 : Floc found but cannot measured (subjective)

Stage 2 : Floc found in small quantity, < 1.0 ml/litre Stage 3 : Floc found abundance, 1.0 – 5.0 ml/litre

Stage 4 : Floc found abundance, 5.1 – 10.0 ml/litre Stage 5 : Floc found abundance, > 10.1 ml/litre

Sampling Method Measuring procedure 1 liter / 2 places/ 15 cm deep/ between 10-12 am

Let it settled for 15-20 minutes

Read density of flocs in cone (ml/l)

‘Floc’ Development Average Floc Development

Floc (ml/L)

14 12 10 8 6 4 2 0 20

30 Floc

40

50

60

70

80

90

100

110

120

130 DOC (days)

Control Biofloc Black gill

Black biofloc

Biofloc- general view at surface Brown biofloc

Green biofloc

What is BFT? We limit water exchange

► Organic residues accumulate ► We mix and aerate. ► Ideal conditions for bacteria ► Bacteria control water quality.

► Fish eat bacteria 

Feed is recycled

Conditions for bacteria There is a lot of available food for bacteria. The pond is loaded with organic residues. ► The pond is fully aerated (needed for proper fish growth). 

The pond is well mixed (typically 24 hours a day)

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The number of bacteria in such ponds is 10⁶ up to 10⁹ Bacteria in one cm3!!!!

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The pond becomes a biotechnological industry – Biofloc Technology

Manipulating bateria Normally, there is enough nitrogen in ponds for new cell production. ► By adding carbohydrates( eg Starch, flour, molasses, cassawa etc) to the pond, heterotrophic bacterial growth is stimulated and nitrogen uptake through the production of microbial proteins takes place.  Then, there is a need for nitrogen.  If carbon and nitrogen are well balanced in the solution, ammonium in addition to organic nitrogenous waste will be converted into bacterial biomass. ► The way to do it: Keep C/N ratio higher than 10 

The bacteria now take the nitrogen from the water and control water quality

Cont….. 

This promoted nitrogen uptake by bacterial growth decreases the ammonium concentration more rapidly than nitrification.



Immobilization of ammonium by heterotrophic bacteria occurs much more rapidly because the growth rate and microbial biomass yield per unit substrate of heterotrophs are a factor 10 higher than that of nitrifying bacteria.

Can we feed fish or shrimp with bacteria? Bacteria are very small. 

Luckily, when we have a dense culture,

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They tend to form bioflocs, containing bacteria, other organisms and organic particles.

Mechanism of floc formation 

The flocculation of microbial communities is a complex process.

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Within the floc's matrix, a combination of physical, chemical and biological phenomena is operating.

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The exact mechanisms and the methods to engineer microbiological flocs remain largely unknown.

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The main constituents that can be found within the floc matrix are the extracellular polymeric substances.

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These structures form a matrix that encapsulates the microbial cells, and play a major role in binding the floc components together.

Cont…..

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They are typically made up out of polysaccharides, protein, humic compounds, nucleic acids and lipids.

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They are produced as slime or capsule layers under various nutritional conditions but particularly in case of limitation by nutrients like e.g. nitrogen.

Factors influencing floc formation and floc structure in bio-flocs technology 

Mixing intensity

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DO

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Organic carbon source

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Organic loading rate

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Temperature

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pH

APPLICATION OF BIOFLOC TECHNOLOGY IN AQUACULTURE

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Nursery phase is defined as an intermediate step between hatchery-reared early postlarvae and grow-out phase.

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Such phase presents several benefits such as optimization of farm land, increase in survival and enhanced growth performance in grow-out ponds.

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BFT has been applied successfully in nursery phase in different shrimp species such as L.vannamei , P. monodon , F. paulensis , F. brasiliensis and F. setiferus.

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Better nutrition by continuous consumption of biofloc

The growth enhancement of L. vannamei post larvae reared in nursery BFT is related to a better nutrition by continuous consumption of biofloc, which might positively influence growout performance of L vannamei . 

Enhance growth performance

-It was observed that presence of bioflocs resulted in increases of 50% in weight and almost 80% in final biomass in F. paulensis early postlarval stage when compared to conventional clear-water system. 

Increased the survibility rate

reported survival rates of L vannamei in BFT nursery pond range from 55.9% to 100% and 97% to100%, respectively.



Maintain favorable water quality and enhance production.

the addition of substrates in BFT systems increased growth and further enhanced production, while also contributing to more favourable water quality conditions. According to the same study, growth and survival was not affected by stocking density (2500 vs 5000 PL/m2), therefore greater production outputs were achieved at the higher density.

The F. brasiliensis postlarvae grow similarly with or without pelletized feed in biofloc conditions during 30-d of nursery phase, which was 40% more than conventional clear-water continuous exchange system. ► Decrease FCR and reducing cost in feed

Grow out 

In grow-out, BFT has been also shown nutritional and zoo technical benefits.

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It was estimated that more than 29% of the daily food intake of L. vannamei consisted of microbial flocs, decreasing FCR and reducing costs in feed.

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The reference showed that juveniles of L. vannamei fed with 35% CP pelletized feed grew significantly better in biofloc conditions as compared to clear-water conditions.

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It was showed that controlling the concentration of particles in super-intensive shrimp culture systems can significantly improve shrimp production and water quality

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Also, the same authors demonstrated that environmentally friendly plant-based diet can produce results comparable to a fish-based feed in BFT conditions.

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It was evaluated the stocking density in a 120d of L. vannamei BFT culture, reporting consistent survival of 92, 81 and 75% with 150, 300 and 450 shrimp/m2, respectively.

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Moreover, the study performed in a heterotrophic-based condition detected no significant difference in FCR when feeding L. vannamei 30% and 45% CP diets and 39% and 43% CP diets, respectively.

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floc biomass might provide a complete source of cellular nutrition as well as various bioactive compounds even at high density.

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It is not known exactly how microbial flocs enhance growth.

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Is well known that protein, peptides and amino acids participate fully in synthesis of new membranes, somatic growth and immune function and biofloc can potentially provide such ingredients.

Application in Breeding 

The BFT has been successfully applied for grow-out, but little is known about biofloc benefits on breeding.

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Biofloc in a form of rich-lipid-protein source could be utilized for first stages of broodstock's gonads formation and ovary development.

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Furthermore, production of brood stock in BFT could be located in small areas close to hatchery facilities, preventing spread of diseases caused by shrimp transportation.

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BFT could enhance spawning performance as compared to the conventional pond and tank-reared system, respectively (i.e. high number of eggs per spawn and high spawning activity

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As an alternative for continuous in situ nutrition during the whole life-cycle, breeders raised in BFT limited or zero water exchange system are nutritional benefited by the natural productivity (biofloc) available 24 hours per day.

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better control of water quality parameters and continuous availability of food (biofloc) in a form of fatty acids protected against oxidation, vitamins, phospholipids and highly diverse “native protein”, rather than conventional systems which “young” breeders are often limited to pelletized feed.

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The continuous availability of nutrients could promote high nutrient storage in hepatopancreas, transferred to hemolymph and directed to ovary, resulting in a better sexual tissue formation and reproduction activity.

 Excess of particulate organic matter covered breeder’s gills and could limit oxygen exchange, might resulting in mortalities

Application in animal food industry 

The cost of diets in several animal cultures is predominantly due to the cost of protein component.

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Fishmeal is prime raw material as a component of aquaculture feed.

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The quality attributed to fishmeal includes high palatability, high content of digestible protein, highly unsaturated fatty acids (HUFA) and minerals.

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Recently the aquaculture industry has been facing some important limitation i.e increasing price of fish meal

pressure on natural stock (overfishing)

Increasing price of fish meal competition with animal cultures (swine and poultry) and differences in quality. 

Aquaculture industry needs to investigate alternative source of proteins to replace less sustainable ones

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The microbial particles can provide important nutrients such as protein , lipids , amino acids and fatty acids.

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Biofloc act as raw material to produce “biofloc meal.

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Biofloc meal (also called “single-celled” protein), added to compounded feed is currently focus of intensive research in nutrition fields.

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However, to produce this protein ingredient some processes are required such as drying, milling and storage.

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In this context, nutritional characteristics could be affected (by i.e. temperature during drying)

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Nutritional composition of biofloc differs according to environmental condition, carbon source applied, TSS level, salinity, stocking density, light intensity, phytoplankton and bacterial communities and ratio, etc

Crude protein (%)

Carbohydr ates (%)

Lipids (%)

Crude fiber (%)

Ash (%)

Reference

43.0

-

12.5

-

26.5

McIntosh D. et all 2000

31.2

-

2.6

-

28.2

Tacon AGJ et all 2002

12.0-42.0

-

2.0-2.8

-

22.0-46.0

Soares R et all 2004

31.1

23.6

0.5

-

44.8

Wasielesky W.et all 2006

26.0-41.9

-

1.2-2.3

-

18.3-40.7

Ju ZY et all 2008

30.4

-

1.9

12.4

38.9

Ju ZY et all 2008

49.0

36.4

1.13

12.6

13.4

Kuhn DD et all 2009

38.8

25.3