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CONSERVATION AND DEVELOPMENT OF KIEN GIANG BIOSPHERE RESERVE PROJECT

GUIDLINES ON POLYCULTURE

OF

SEA-BASS WITH TILAPIA

Kien Giang, 5/2013

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Foreword

Kien Giang is located in the Mekong Delta and since 85% of the land area is less than one metre above sea level, most of the people live in low-lying areas which are at particular risk from rising sea levels and the increased frequency and intensity of natural disasters, such as typhoons, storms and floods. Economic pressure, poverty and the lack of knowledge result in non sustainable use of the coastal resources. Further, the rapid population growth has resulted in a very high pressure on the natural resources of the inland and coastal forests which were of very high biological diversity.

Seabas is a fish species with high economic value, and are able to survive and grow in both salt and fresh water conditions, and are considered a good and suitable species for farming along Kien Giang coastal area in terms of climate change.

This handbook "guideline on polyculture Seabass with Tilapia" is a collection of specific, detailed, realistic instructions to help farmers to success, improve income, poverty reduction, and lessen the dependence on natural resources

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I. WHAT IS POLYCULTURE

This culture approach shows great promise in reducing, if not totally eliminating the farmers' dependence on trash fish as a food source. The method is achieved by simply incorporating a species of forage fish with the main species in the pond. The choice of Tilapia as forage fish depends on its ability to reproduce continuously and in a quantity sufficient to sustain the growth of the Seabass throughout the culture period. The Tilapia use natural food produced in the pond and does not compete with the main species in terms of feeding habit.

II. THE BENEFIT OF POLYCULTURE

Low investment: This model suits people who live in rural, remote areas, particularly farmers that have tough financial conditions. In the local waterways, there is an abundant supply of tilapia that provides a food source for the target species, seabass. Farmers do not have to buy food for the seabass because tilapia is likely to already be available in their ponds or they just need to take time to catch the fish in local waterways. In rural areas every household already has either fish ponds or a canal surrounding their land. There is no need for high level of investment, they can simply renovate their existing ponds and buy Seabass fingerlings.

Simple culture techniques: Unlike monoculture production, or intensive culture, farmers do not require a high level of knowledge and skill in feeding and management of pond conditions.

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III. SOME INFORMATION ABOUT THE SEAS-BASS

Body elongated, compressed, with deep caudal peduncle.

Maximum body size is 2m long, 60kg weight

The fish can survive and develop well in fresh – brackish or salt water. At maturity fish migrate offshore to the sea for spawning. After hatching, the fingerlings will return to estuaries and fresh water basins to grow.

Favorable conditions for sea bass are 15 - 280C in temperature, 2 - 35‰ in salinity, 1.2 - 2m in depth.

It is a carnivorous fish, eat small fish, shrimp, or crustacean …

Has a high growth rate, after one year from 4 – 5cm long fingerling can reach to 1.5 – 3kg/fish.

Seabass is widely distributed in tropical and sub-tropical areas of the Western Pacific and Indian Ocean, between longitude 50°E - 160°W latitude 24°N – 25°S. It occurs throughout the northern part of Asia, southward to Queensland (Australia), westward to East Africa.

In Viet Nam the fish distribute along the coastal from North to the South.

In the early life stages (1.5–2.5 kg body weight) majority of the Seabass appear to be male but when they attain a body weight of 4–6 kg majority become female.

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IV. POND DESIGN

Seabass ponds are generally rectangular in shape with

Size is ranging from 1000 m2 to 2 hectares and depth of 1.2 to 1.5 meters.

Each pond has a separate inlet and outlet gate to facilitate water exchange.

The pond bottom is entirely flat lsloping toward the drainage gate

Ponds should be near the canal, but better if it is in the medium to high tide, to facilitate drainage.

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V. STEPS IN POND PREPARATION

1. Drain water completely, repair pond dykes, fill holes or leaks around the dykes.

2. Apply lime powder at dose of 10-15kg/100m2 to kill disease and increase pH, dry pond bottom for a period of 3 – 5 days.

3. Fill ponds with water through a filter bag to prevent predatory species for entering the pond. Fill to level 30 – 40cm.

4. Create conditions to allow algae multiply and act as natural feed for the tilapia. To do this add organic fertilizer (chicken manure) at the rate of 1 ton per hectare or artificial fertilizer at doze of 20kg N.P.K/ha and 7kg Ure/ha.

5. Increase water depth gradually for the propagation of natural food for seabass. When an abundance of natural food (algae) is observed, release selected tilapia broodstock into the pond at the rate of 5,000–10,000 per hectare. Sex ratio of male to female is 1:3.

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The tilapia are reared in pond for 1 to 2 months or until tilapia fry appear in sufficient number.

6. When there is sufficient tilapia fry, stock the pond with Seabass juveniles.

VI. CHOOSING AND STOCKING FINGERLINGS 1. Choosing fingerlings

Fingerlings should be uniform in size to minimize loss due to cannibalism.

The larger size fingerlings are best for culture. They should not be smaller than 4-5 cm long.

Fingerlings should be healthy with no chaffing and no deformities. Healthy fingerlings are active, swim fast and react quickly to external impacts.

Uniform

size fry

Healthy

fry

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2. Fingerling transportation

Normally the hatchery will lower the water temperature before packing and transporting. request 200 fish/bag size of 4-5 cm long.

During transportation the bags must be laid horizontally to create more space for fish and surface area for Oxygen absorption into the water for fish breathing. Never lay the bags vertically because it leads to reduced space, low dissolved oxygen, and fish will become weak and die during transport.

Lay the bags

horizontally

to transport Bọc xắp ngang (đúng)

Never lay bags

vertically to

transport

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Acclimatizing and stocking

Two days before stocking, buyers should inform the hatchers of the salinity level in their ponds. The hatchery will adjust their salinity before sending fingerlings to the farm. This will avoid salinity shock when are placed in farmer ponds.

As mentioned above, the hatchery will lower water temperatures for transporting to reduce oxygen consumption, so before stocking farmers need to leave fish bags on pond water surface for 15 - 30 minutes to balance the temperature.

Then, farmers can release fish directly to the pond by opening the bag and allow the fish to slowly swim out. If possible, acclimatize before releasing into the pond:

Acclimatizing tools: a container (large basin or clean jar) and air aerator. Process: pour all fish into the container with aerator, every 5-10 minutes take a little water from the pond and put it into container to acclimate fish to pond conditions, repeat the process over one hour until all water in the container is from the pond.

Stocking should be done in the evening or before 8am in the morning. Take plenty of time to transfer and acclimatize. At night or early morning the weather is cool and stable.

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3. Nursing in net cage

To improve the survival and grow rate, for the first two months of culture, farmers should make a net cage to stock and feed the fry. The net cage should be placed in the grow-out pond for better management.

The size of net cage depends on the number of fry. There must be enough space for the fish.

During this early stage, feed is trash fish; trash fish must be fresh. Chopped trash fish are given twice daily at 8:00 AM and 17:00 PM at the overall rate of 10% of total biomass in the first two months of culture.

One month later:

1. Count the living fish

2. Catch uniform size, bigger fry and release to the pond.

3. Keep feeding the remain fry

15 days later (1,5 month of culture):

1. Count the living fish

2. Catch uniform size bigger fry and release to the pond.

3. Keep feeding the remain fry

15 days later (2nd moth of culture)

1. Count the living fish

2. Release all into the pond

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VII. POND MANAGEMENT

Due to the need to maintain natural food (algae) in the ponds, water replenishment in a polyculture system should be minimized. Water exchange should be done once in three days for about 30% of pond capacity.

Periodically estimate the growth rate of the fish, monitor the changes in environmental factors, eating status.

Regularly check the dykes, inlet and outlet, especially in the rainy season, to avoid the loss of fish escape.

VIII. FEED AND FEEDING

Supplementary feed is not required in the polyculture system.

In addition, farmers can feed trash fish if trash fish are available. In this case, the trash fish need to be chopped into small pieces, and scatter around the pond.

XIX. HARVEST

The best way to harvest is completely pump out the water and catch all fish, and then prepare the pond for next crop.

Otherwise, farmers can use a net to harvest all the fish.

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XX. DISEASE PREVENTION AND TREATMENT In any kind of culture, disease prevention is very important, especially in this kind of culture. In aquaculture, the treatment is indirect through food, or water, so a large amount of drugs will be dissolved in water, leading to waste. Furthermore, in this culture the density is only 0.5 to 1.0 fish/m2, so this kind of treatment is wasteful and does not have high efficiency.

1. Disease prevention

Choose healthy and uniform sized fry

Stock at an appropriate density, do not over stock.

Ensure the water level is kept stable with a depth of at least 0.9 m, because low water will cause unstable water conditions that become too hot in sunny weather, or too cold in the rain. The changed conditions result in shock to the fish and leads to slow growth, disease or loss of production.

Good pond preparation techniques before stocking includes cleaning of bottom material which contains disease organisms and leads to dirty water.

Maintain pond water color, greenish for fresh water, and brown-yellowish for brackish, so it has enough natural feed for the tilapia.

As soon as disease is detected - diseased fish or fish with signs of illness, farmers should empty the pond of fish immediately.

Once the all fry are released, feeding is not needed, if farmers feed trash fish, the feed must be clean, healthy and fresh, and should avoid un-needed trash that will pollute the water.

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2. Disease treatment As mentioned above, chemical treatment is not very effective. However in the next section we describe the common diseases and treatment for reference. The dosages and how to treat is follows the instructions on the packaging of the drug. a. Parasitic worms on fish gill

Treatment chemical: BKC, Praziquantel

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b. Fish louse disease Treatment chemical: CuSO4 or BKC, FIBA,

Praziquantel

c. Anchorworm in fish gill Treatment chemical: FIBA, Praziquantel

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d. Leech Treatment chemical: Formaldehide, Praziquantel.

e. Blood spots due to Streptococcus Bacteria

Treatment chemical: Flophenicol.