ASEAN Cooperation in Food, Agriculture and Forestry

HARMONIZATION OF HATCHERY PRODUCTION OF Penaeus monodon

IN ASEAN COUNTRIES

F i s h e r i e s P u b l i c a t i o n S e r i e s No.3

CONTENT

1. INTRODUCTION

2. CURRENT STATUS

3. SITE SELECTION3.1 Water Supply3.2 Near the Aquaculture Site and the Market Place3.3 Transportation3.4 Electricity and Communication3.5 Natural Disasters3.6 Security

4. HATCHERY DESIGN4.1 Size of Hatchery4.2 Water Supply4.3 Aeration System

5. SPAWNERS5.1 Source and Abundance5.2 Maturation Techniques5.3 Feed and Feeding5.4 Health Maintenance of Spawners

6. HATCHERY TECHNIQUES6.1 Japanese Technique6.2 Galveston Technique6.3 Taiwanese Technique6.4 Modification of the Technique by Each

ASEAN Country

7. FEED AND FEEDING7.1 Feed7.2 Feeding

8. WATER QUALITY MANAGEMENT

9. HEALTH MANAGEMENT

10. HARVESTING AND HANDING10.1 Harvesting10.2 Sampling Method

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10.3 Packing10.4 Handling

11. BIBIOLIGRAPHY

ILLUSTRATION AND TABLE

Figure 1: The Laboratory and the Outdoor Culture of Skeletonema sp.

Table 1: Optimum Ranges of Water Quality for Rearing Penaeid Shrimp Larvae

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HARMONIZATION OF HATCHERY PRODUCTIONOF Penaeus monodon IN ASEAN COUNTRIES

1. INTRODUCTION

In 1934 Dr. Fujinaga, the world’s acknowledged father of shrimp culture, successfully spawned and partially reared the larvae of Penaeus japonicus in Japan (Hudinaga, 1942). In 1963, Mr. Cook of Galveston Laboratory in Texas, United State of America in collaboration with Dr. Fujinaga, successfully spawned and reared the larvae of two American species, P. Setiferus and P. Aztecus (Cook and Murphy, 1966). The spawning technique was later adopted and used by many hatcheries in Asia which include Taiwan, the Philippines, Thailand and Malaysia. Species of shrimp that have been produced in those countries are local species such as P. monodon, P. merguiensis, P. indicus and P. orientails. The technique now is modified for proper larval production practice by combining the advantages of both Japanese technique and Galvaston technique such as done in Taiwan, the Philippines, Thailand and Malaysia.

2. CURRENT STATUS

It was reported by ASEAN Shrimp News (Issue, No. 20, 1994) that there were approximately 3,700 shrimp hatcheries in ASEAN countries in 1994. At least 96,000 shrimp spawners are required each year to supply the hatcheries to produce over 54 billion of shrimp larvae. It is inevitable that the demand of shrimp fry for shrimp culture industry would be increased sharply in the near future particularly in India, Vietnam and Bangladesh where shrimp farming is rapidly expanding. To supply adequate amount of shrimp fry for shrimp farming industries in the region, good shrimp hatchery practice manual should be published.

The purpose of this manual is to compile the information on the appropriate shrimp hatchery techniques from different ASEAN Member Countries to be used as a guideline for shrimp hatchery practice.

3. SITE SELECTION

The criteria for site selection for shrimp hatchery are as follow:

3.1 Water supply

Seawater supply should be clean, clear and relative free from silt and pollution. The quality and quantity of seawater must be suitable for hatcheries work. The salinity should be around 28-33 ppt (for dilution process, up to 120 ppt is usable).

Fresh water is necessary to control the salinity of plankton culture and nursery or acclimatization of fry during transportation to farm pond area. Fresh water is also used for cleaning equipment.

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The hatchery should be located away from water pollution sources i.e. industrial areas and urban communities which release industrial and domestic waste to the water source.

3.2 Near the Aquaculture Site and the Market Place

The hatchery should preferably be located near the farm pond area to minimize transport duration and stress to the seed and to ease marketing of product. The hatchery should be located near a place where essential materials are available for hatchery, such as feed for broodstock and fry, tools, equipment and other facilities. Source of spawner for constant supply is also taken into consideration in hatchery site selection.

3.3 Transportation

The hatchery should be accessible (by road, plane or boat) for convenience in transportation of spawner, nauplius and postlarvae to and from the hatchery. It should also be convenient for distribution of spawners or nauplius to the hatchery and for distribution of post larvae to the farm.

3.4 Electricity and Communication

The hatchery should be provided with a reliable electric power supply for all electric equipments, i.e. water pump, air blower, laboratory equipment, hatchery light etc. Stand-by gasoline engine generator must be available in case of electric power failure.

Telephone communications are also essential for the hatchery in order to facilitate consultations with experts in emergency situations and to make urgent orders of hatchery supplies, such as spawner, nauplius, feed, chemicals and drug.

3.5 Natural Disasters

The location of the hatchery should be carefully selected to avoid natural disasters such as storm, high waves and strong winds to prevent damages and destruction of the facilities and equipments.

3.6 Security

For security, the hatchery should be placed far from sensitive areas where poaching can be prevented. The electric circuits and electric equipments should be supplied with a safety cut.

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4. HATCHERY DESIGN

The design of the hatchery should be simple, economic, neat, compact and easy to be operated with maximum efficiency. The materials used should be locally available, cheap and long lasting. It can be made from a wide range of materials: reinforce concrete, ferro concrete, fiberglass and wood with plastic lining for example.

There is no specific pattern for layout of the hatchery. The arrangement of tanks and working spaces should be based on working performance to save time and labour during the operation. The hatchery should be covered to protect against rain and sunlight and also to keep certain level of temperature.

4.1 Size of Hatchery

There is no limitation in size of hatchery, as long as there is space for broodstock or maturation tanks, spawning tanks, larvae rearing tanks, nursery tanks and algae or food organisms rearing tanks. Normally, there are three sizes:

4.1.1 Small-scale Hatchery

This type usually has a total rearing capacity of 100 – 200 cubic meters, and each tank has a capacity of 10 – 15 cubic meters, 1-1.8 meters in depth and in any shape (circular, rectangular or square). The construction materials are concrete, ferocement, fiberglass or others. In most of the hatcheries, its water temperature is controlled by covering the tanks with black canvas or tile. The size of small-scale hatcheries is meant to suit the farmers and are usually located in the coastal areas. Some hatcheries are modified from Macrobrachium hatcheries. Most of them are located far from the coastal area. They generally use hyper saline water from salt farms, and subsequently dilute to the desired salinity.

4.1.2 Medium-scale Hatchery

A medium-scale hatchery has the total tank capacity of 201 – 500 cubic meters. It was developed by combining the best features of small-scale and large-scale hatcheries. The rearing tanks usually have a capacity of 10 – 25 cubic meters, 1.5 – 2.0 meters depth and in any shape. The rearing tanks are usually placed outdoor and covered with black canvas and equipped with heater for temperature control. Water temperature can also be controlled by covering the tanks with black canvas inside a plastic covered house to save electricity.

4.2 Water Supply

The sea water supply system consist of a water intake pipeline, water pump and reservoir. A single pipeline is required for the seawater intake system. For small – scale hatchery with 10 to 15 tanks, a 2 hp. electric pump and a 10 to 15 ton reservoir should be adequate to supply sea water for the hatchery. For the medium-scale hatchery and the large-

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scale, stainless steel pump with a capacity of 50 m3/hr of seawater is required. Two submersible pumps with a capacity of 2 hp are also needed.

However, if clean sea water is not available, sea water should be pumped and supplied through a sand filter or through the bag filter, and chlorinated with 50 ppm hydrochloride overnight, and neutralized with sodium thiosulfate before using.

4.3 Aeration System

An air pump should be available all the time in the hatchery. The aeration system can be either low pressure with high volume given by a roots air blower, or a high pressure with low volume type given by a compressor. The farmer generally preferred less complicated equipment which oil-free air because it is save to use. For the small-scale hatchery, the ordinary cylindrical air blower is sufficient, since the oil introduce into the system has no significant impact on shrimp larvae. For the culture tanks where the maximum depth is less than two meters, an air pressure of about 0.2 – 0.3 kg/cm2 is enough. The capacity of the aeration system depends on the size of hatchery. For a 1-m deep tank, a 3.6 liter/min/m2 of air is enough to ensure oxidation of the high organic load in the rearing tank.

There are many techniques to aerate the tank. One technique is to connect an Eslon rubber air tube with an air stone. One air stone is adequate for 0.5 m2 of water area. Another technique also uses an Eslon tube. The tube is drilled to make several holes for air diffusion which is placed on the bottom of the tank. Air is injected into the water through these holes.

Aeration should be operated at all time during nursery period. Therefore, a battery-powered or gasoline generator must be installed to be an alternative power supply in case of power failure.

5. SPAWNERS

5.1 Source and Abundance

In Thailand, shrimp broodstock, gravid females for artificial seed production in hatcheries come from the wild. They are captured by trawler at the depth of more than 40 m, 100 – 150 km. offshore in the Andaman sea. The peak season to capture gravid female is normally from December to March and June to September. It is relatively poor to catch gravid female during the monsoon period. As shrimp fecundity and egg quality increase with body size, the good quality brooder therefore must be larger than 23 cm. with various stages of maturity eggs. The brooders are kept in the holding tanks on board with aeration system. Transportation of shrimp brooders to the hatchery is made shortly after the trawler arrived at the port. Normally, 4 – 10 brooders are packed in plastic bag with oxygen at a temperature of above 20 – 220C. Shrimps can survive in a good condition for 6 – 8 hrs after catching.

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5.2 Maturation Techniques

Kungvankij (1982), Tiensongrusmee (1982), Primavera (1982) reported that three basic techniques, including eyestalk ablation, nutrition and manipulation of environment, are used separately or in combination to induce shrimp maturation. Gravid females with weight over 100 g are mostly used for eyestalk ablation. After eyestalk ablating the brooders are then released in the maturation tanks with unablated male. Generally, the sex ratio is maintained at 1 – 2 males to 1 female, and stocking rate is 5 – 8 shrimp/m2. Shrimps are kept in these tanks until the gonad is conditioned, usually about 3 – 7 days after the eyestalk ablation. The frequency of broodstock examination in the tanks varies from daily to every other day. After the gonad has developed to stage II and stage IV, the shrimp will be transferred to the spawning tank which is equipped with an aerator. After spawning, the shrimp will be returned to the maturation tank again to remature the gonad for subsequent spawning.

The maturation tank can be of any shape (circular, rectangular or square) and any size varying from 5 – 50 tons in capacity, 1 – 2 meter in depth. Construction materials including concrete, ferrocement, fiber adjusted in suitable conditions and maintenance of water quality by regular siphoning out of debris, etc. Water may be flown through, recirculated or with regular (daily, twice a week, etc.) renewal. Normally, the maturation tanks are covered with black canvas or kept inside the house to reduce stress and to easily check gonad stages by using flashlight.

5.3 Feed and Feeding

Molluscs meat, including mussel, clam, cockle, crab and squid meat, are the most common food for the broodstock. Other food items are those of fresh or frozen with high protein contents (40 – 60%) marine worms, mysid, shrimp and dried pellets. These foods may be given individually or in combination with daily feeding rate of approximately 10 – 30% or 3 – 5% of shrimps weight for wet feed and dried feed (pellet), respectively. Feed should be given up to four times a day and the daily ration is divided accordingly.

5.4 Health Maintenance of Spawners

Prevention of diseases through proper nutrition and maintenance of good water quality is more important than control. However, bacterial diseases such as zoothamnium and fungal diseases can be controlled through application of antibiotic or chemicals such as:

Bacterial diseases

a. Oxytetracycline 1.0 – 5.0 ppm baths for 3 – 5 daysb. Furazolidone 1.0 – 5.0 ppm baths for 3 – 5 days

10 – 20 ppm baths for 24 hoursc. Chloramphenicol 1.0 – 3.0 ppm baths for 3 – 5 days

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Zoothamnium diseases

a. Fomalin 40% 25 – 50 ppm baths for 24 hours

Fungal diseases

a. Malachite green 0.01 ppm baths for 24 hours0.05 ppm baths for 10 minutes

b. Treflan 0.01 ppm baths for 24 hours

6. HATCHERY TECHNIQUES

6.1 Japanese Technique

In Southeast Asia, Japanese technique which was established by Kittaka in 1994 is widely used in most hatcheries. It is based on the idea of utilizing natural occurring diatoms in the rearing pond as food for the larvae. To ensure adequate growth of the diatoms, water in larvae rearing tanks is enriched daily with fertilizer. The rearing tanks are either of rectangular or square shape with a capacity of 40 – 2,000 cubic meters, 1.5 – 2.0 meter depth and is normally located outdoors or indoors. For indoor tanks, partially transparent roofing is provided to allow sunlight penetration. In this system, spawning, larvae rearing and nursery operation are operated in the same tank. Technical grade fertilizers are applied directly to the tank after removal of spawners and hatching of eggs.

The spawners are kept in the holding tanks before being placed into the hatching tanks. The volume of water in hatching tanks varies from species to species. The normal practice for P. japonicus is one spawner/2 m3, p. monodon is one spawner/5 m3, and p. indicus and p. merguiensis is one spawner/ m3. An initial water level of 100 cm is generally maintained. Spawning usually occurs at night that they were transferred from holding to the hatching tanks. After spawning the brooders are then removed in the early morning of the following day. If there is a few number of eggs or nauplii, the spawner may be left in the tank for another night. Soon after hatching, 3 ppm KNO3 and 0.3 ppm Na2HPO4 are applied as fertilizer. The amount of fertilizer applied thereafter depends on the density of plankton. During this stage, about 10 – 20 cm of fresh clean water is added daily depending upon the density of plankton. If the density of plankton is low, soybean cake, soybean curd, egg yolk, or fertilized eggs of oyster are given as supplementary food. Shrimp larvae begin to feed on the plankton when they reach the protozoa stage. During the mysis stage, they are fed with rotifer (Brachionus plicatilis) or brine shrimp (Artimia salina) nauplii. Once the post larvae reach PL6, they are fed with minced mussel, clam meat or formulated larvae feed with corresponding decrease in ration quantity of brine shrimp nauplii until they reach P9. Beyond this stage, the larvae are feed solely with minced mussel, clam meat or artificial diets 3-4 times a day. To ensure sufficient amount of algae in the rearing tank, pure cultures of diatom are used before the application of fertilizer. The advantages and disadvantages of these systems are :

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Advantages :i. The larvae can be raised up to PL 22 in the same tank;ii. Nursery tank is not necessary;iii. Less labour required for operation; andiv. Low cost of maintenance.

Disadvantagesi. High cost of initial investment;ii. Difficult to control disease; andiii. Large number of spawner is used in one operation.

6.2 Galveston Technique

This technique was developed in 1960 by the Nation Marine Fisheries Service in Galveston, Texas, USA. It utilizes separate algae and diatom culture to control the feeding of shrimp larvae. Due to inconsistent supply of spawners, the hatchery is much smaller in size than in the Japanese technique. Spawning tanks and larva rearing tanks are separated. Both types of tanks are made from plastic or fiberglass. The capacity of larvae rearing tanks range from 1,000 – 2,000 litre and the spawner tanks from 100 to 250 litre. The stocking density is so high (200 – 300 nauplii/l) that the larvae can only be reared up to PL1 – PL5. Earthen ponds or concrete tanks are necessary for further rearing of juvenile before stocking in grow-out pond. In the larvae rearing tanks, alga cell are added daily during the protozoea stage and newly hatched artemia are given during the mysis and early post larval stage. The advantages and disadvantages of these systems are as follows :

Advantages :i. Low initial investment;ii. Small number of spawners is required;iii. Nauplius (N) to post larvae (PL), could be reared in high density; andiv. Easy to control disease

Disadvantages :i. It is difficult to raise larvae up to PL 22 is same density;ii. Nursery ponds are required; andiii. In the case of mass production higher manpower is needed.

6.3 Taiwanese Technique

The rearing tanks range from 20 – 50 m3, either indoor or outdoor is used in this technique. The tanks are usually covered with canvas and equipped with heaters to control temperature. Shrimps larvae are fed with Skeletonema sp. or microencapsulated feed instead of Chaetoceros. At this stage antimicrobial is applied to control the disease.

Spawners are placed in the spawning tanks with low level of aeration. They will spawn during the night. After spawning, the water is stirred by using the paddle for 15 – 20 minutes/time until the eggs are hatched out. Then the eggs are sampled in order to estimate

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the numbers of nauplii. The nauplii are collected after stopping the water circulation and then lighting is applied to the hatching tank. The nauplii will swim up to the water surface toward the light. After that nauplii, are collected and transferred to the rearing tanks. Water temperature inside nursery tanks is controlled at 32 – 34 0C by covering with black canvas. Nauplii are fed daily with alga cells (Skeletonema sp.) and microencapsulated feed during the mysis stage. Newly hatched artemia and microencapsulated feed is given during the post larval stage.

6.4 Modification of the Technique by Each ASEAN Country

a. ASEAN countries modified the technique by combining the advantages of Japanese and the Galvaston techniques together. The spawning tanks with capacities of 1,000 – 3,000 l and the nursery tanks with capacity of 30 – 100 m3 are capable for rearing the larvae up to PL30. The spawners are placed in the spawning tanks and removed from the tank in the early morning after spawning. The eggs are collected and washed, or 2/3 of water in the tank is drained from the spawning tank through filter nets and then replenished with fresh water and leave the eggs to hatch in the same tank. The number of hatched nauplii is estimated. If the average nauplii after hatching is more than 0.5 million (or 20 – 30 nauplii/l) then the nauplii are transferred into a larger tank (20 – 100 m3). In this new tank, the larvae are reared until PL 25. If the bigger tank is not available for the large number of larvae ( 100 – 200 larvae/l) the larvae are reared up to PL2 – PL6 and then transferred to the large tank.

b. The technique is also modified to increase the efficiency of Taiwanese technique. Generally, the technique is as described in (a) but the nursery tank is covered with canvas and water temperature controller. The water temperature is usually controlled at 32 – 34 0C. The nauplii are transferred to nursery tank and fed with Skeletonema sp. and microcapsulated feed. Newly hatched artemia and microcapsulated feeds are used in post larvae stage.

7. FEED AND FEEDING

7.1 Feed

The type of feed for shrimp larvae depends on the availability at each location. Normally, the cheapest food with the best output which is available all year round will be selected. There are many types of feed which are used in hatcheries such as:

7.1.1 Live Feed

a. Phytoplankton (Skeletonema sp., Chaetoceros sp. and Tetraselmis sp.) Phytoplankton is used during zoea stage. For the culture of diatom, there are two steps.

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a.1 Laboratory Culture:

The Guillard’s media, Convey’s media: Provasali media, and Sato and Serikava media are most often used. In this manual, the culture media adapted from Sato and Serikava media are recommended. _____________________________________________________Stock solution amount/1L seawater_____________________________________________________

NaNO3 100 g/L 1.0 mlNa HCO3 168g/L 0.5 mlNa2 SiO3 15g/L 1.0 mlNa2 HPO4 12 H2O 100 g/L 0.1 mlVitamin B12 1,000 gm/100ml 1.0 mlPL Solution 1.0 ml

PL Solution consist of :Distill water 1,000 mlNa2EDTA 3.00 gmFe Cl3 6 H2O 0.24 gmZn Cl2 0.03 gmMn Cl24H2O 0.27 gmCo Cl2 6H2O 0.08 gmCu SO45H2O 0.04 gmH3BO3 3.44 gm

a.2. Outdoor Culture:

There are two formulas of culture media which are used in hatchery.

KNO3 100.00 gmNa3 HPO4 10.00 gmFe Cl3 2.50 gmNa2 SiO3 5.00 gmSeawater 1.00 m3

Urea (46-0-0) 60 gm/m3

N.P.K. (15-15-15) 30 gm/m3

Na2 SiO3 15 gm/m3

The chemicals of the selected formula are dissolved in water in the diatom culture tank. Stock diatom is then added into the tank. Aeration of the water is required. Within 1-2 days the diatom will have multiplied.

The diagram for the laboratory culture of diatom both indoors and outdoor is shown in the Figure 1.

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Figure 1 : The laboratory and outdoor culture of Skeletonema sp.

3-4 days

(temp. 25

b. Zooplankton (Artemia and rotifer)

Zooplankton is used for the mysis and post larval stage.

Artemia

Artemia is nutritious and suitable for larvae, but it is very expensive and must be imported in the form of cysts in vacuum cans. The cysts must be hatched in seawater with high aeration system. The amount of artemia cysts used is at 2 gm/l of sea water. The eggs will hatch out within 24 – 48 hours and egg shells must be removed thereafter. By stopping the aeration and the shells will float to the surface. The Artemia larvae are then siphoned out of the hatching jar. These Artemia should be treated with 100 mg/l formalin for 1 hour before feeding to the larvae.

In some hatcheries, the Artemia cysts are decapsulated with bleaching powder (Ca(OCl)2 and CaO or Na2CO3 before hatching. Decapsulation of Artemia cysts was first described by Sorgeloos et. Al. (1977) with the following procedures.

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Test tubeSkeletonema 1-2

drops+

Seawater and fertilizers 10 ml.

Flask 250 mlSkeletonema 10 ml

+Seawater and

fertilizers150 ml

Flask 1000 mlSkeletonema 150

+Seawater and

fertilizers850 ml

Bottle 4000 mlSkeletonema 500

ml+

Seawater and fertilizers3000 ml

Skeletonema 2.5 x 106 cel/ml.

For feeding the larvaeor culturing diatom

in ration 1: 10 or 1 : 20

Concrete tank 10 m3

Skeletonema 500 l+

Seawater and fertilizers10 m3

Fiberglass tank 1 m3

Skeletonema 12 l+

Seawater and fertilizers900 m3

5-7 days 3-4

days2 day

1-2 days 2-3 days

Out door Skeletonema culture

Laboratory Skeletonema Culture (temp. 25O C

Preparation of decapsulation solution-bleaching powder Ca(OCl)2 as active ingredient is dissolved in water, and aerated for 10 min. Then technical CaO or Na2CO3 is added to stabilize the pH of decapsulation solution and then the whole solution is aerated for another 10 min. The solution mixture is then stored overnight for precipitation and cooling. The supernatant is siphoned off in the next morning and used for decapsultation.

The ratio of cysts to bleaching powder is 5g bleaching powder per 10 g cysts, and the ratio of cysts to sodium carbonate or calcium oxide is 7 g technical Na2 CO3 or 3 g technical CaO per 10 g cysts.

During decapsulation treatment period, the cysts are kept in a decapsulation container, which is cylindroconical in shape, wholly made of stainless steel mesh (150 m mesh size), with aeration to optimize the circulation in the container. The only hand work required during the decapsulation process is consecutive transfer of the decapsulation container to sequential baths of seawater, hypochlorite, tap water, chloric acid and finally tap water. These steps are itemized below.

i. At first, hydrate the Artemia cysts in sea bath for 1 hour and transfer the cysts to the decapsulation bath, where the cysts are kept for 5 to 10 min to allow complete reaction to take place. During this step, the hypochlorite is kept at a temperature below 35 0C by continuous circulation though a cooling element which consists of a copper coil submerged in bath of salt and ice.

ii. Transfer the decapsulated cysts to the washing bath and wash thoroughly with tap water

iii. Resuspend the decapsulated cysts in the deactivation bath (0.1 N of HCl or Hac solution) for a few minutes for the deactivation of the chlorine residues which remain absorbed on the decapsulated cysts even after through washing with tap water.

iv. Finally, wash thoroughly with tap water. The decapsulation cysts are now ready for incubation under optimal hatching condition.

Rotifers

Rotifers are smaller than Artemia in size and suitable for mysis larvae. Normally Rotifer is fed with green Chlorella sp. as food. The procedure to produce Chlorella is very similar to diatom production but the type of fertilizer used is different.

This fertilizer consists of:

Ca3 (PO4)2 15 gm/m3 sea waterNH4S2O4 100 gUrea 5 g

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There are two major methods for the mass culture of Rotifer, according to the size of the tank and the process of harvesting. One is the Changing Tank Method and the other one is the Partial Harvest Method.

Tanks of 0.5 – 3 m3 capacity are used in the Changing Tank Method. At the onset, one tank (tank A) is inoculated with Chlorella. After Chlorella density reach 1 x 107 cells per ml., Rotifers are added at a density of 10 – 20 individuals per ml. When green water is used and becomes clear, bread yeast is given twice daily at a ratio of 1 gm yeast to 106 Rotifers: When the density of Rotifer exceeds 100 individual per ml. (about 5 – 7 day after inoculation), larger volume is harvested and used to feed the shrimp larvae. The smaller volume is retained to serve as inocula for another Chlorella tank (tank B). Thus, the process is that of transferring from tank A to tank B, B to C. C to D and so forth.

In the Partial Harvest Method, a number of separate large tanks for the mass culture of Chlorella and Rotifers are needed e.g. two 50 m3 Chlorella sp. culture tanks along with several 10 m3 Rotifer culture tanks. Initially, the Rotifers culture tank is inoculated with Chlorella sp. and brought the density up to 1 – 2 x 107 cells/ml. The Rotifers are then inoculated at a density of 10 – 20 ind./ml. As soon as the Rotifers density exceeds 100 ind./ml, 1/5 to 1/3 of the volume is harvested depending on the density of the Rotifers. An equal quantity of Chlorella sp. Culture ( 1- 2 x 107 cell/ml.) is then added. The Rotifer can be harvested daily with the no. 200 mesh size (75 m) plankton net. One larvae at the mysis stage consumes about 100 – 300 Rotifers per day.

7.1.2 Supplementary Feed

a. Milk, boiled egg yolk and egg custard; for the zoea and mysis stage.

b. Egg custard, shrimp meal, mussel, clam meal, screened fresh fish, squid and cockle are used for the post larval stage.

c. Microencapsulated feed is used for the zoea to post larval stage.

d. Pellets (30 – 40) percent protein) of 100 size is used for the post larval stage.

7.2 Feeding

Nauplius stageDuring this stage, the nauplii utilize food stored in their yolk sac. For the typical

system, diatoms are also supplied to the hatcheries tanks in order to make their population grow to the zoea stage.

Zoea stage

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Larvae in this stage could be fed with various kinds of food. Normally, they are fed with phytoplankton such as Chaetoceros sp. From zoea 1 – 3 (some hatcheries fed until mysis 3) at the density of 10,000 – 50,000 cells/ml. artificial formulated feed (microencapsulated feed), boiled egg yolk, milk or egg custard can be used as supplementary feed, but the grain size must suit to size of the mouth larvae.

Mysis stage

For mysis stage, the larvae should be fed with rotifer (Branchionus plicatilis). The number of rotifers required depends on the density of shrimp larvae. Usually the density of 5 – 10 ind. Rotifer/ml is adequate. Each larva consumes about 100 – 200 rotifers per day. If rotifers are not available, Artimia nauplii, boiled egg yolk ( 20 – 150 ; ave 50 ) at 15 – 25 particles/ml and microencapsulated feed can be fed to the mysis larvae instead.

Post larvae

Rotifers, Artimia and micro capsulated feeds are used to feed shrimp in the early stage of post larvae (about 4 – 5 days) and egg custard or shrimp meat, mussel or clam meat, screened fresh fish or cockle are used as food in the stage.

Shrimp is fed 3 – 6 times a day, some time an extra meal is given during the night.

8. WATER QUALITY MANAGEMENT

Water quality in the rearing tanks has to be monitored and maintained in a good condition. The following procedure is recommended.

a) The water quality should be checked daily and monitored during the period of rearing of the larvae.

Water supply by using the sand filter or bag filter and 50 ppm chlorinated over night, neutralized with thiosulfate.

Water temperatureby using heater to control temperature

Salinity by using freshwater dilution to suit salinity

pH by using lime

NH4-N or NO2-N by using formalin or changing the water frequently

b) To keep the water in good quality for the larvae, remove the excess and uneaten food by siphoning out from the bottom of tank and changing the water about 30 – 50% to dilute the toxic.

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c) Cover the tank with black canvas to control water temperature and to keep plankton blooming.

9. HEALTH MANAGEMENT

The larvae are normally sensitive to the changes of the environmental condition. The most important factors are water temperature, salinity, pH, the amount of nitrogen compounds (NH3 –N, NO2-N) and diseases.

To maintain good condition for rearing larvae, the following works should be done.

a) Water temperature, salinity, pH, nitrite-nitrogen and ammonia – nitrogen in water should be checked daily and adjusted.

b) Starvation of shrimps should be avoided and excess food should be avoided not to pollute the water

c) For disease prevention, all rearing tanks and utensils should be properly cleaned or totally sterilized by chlorination

d) For larvae health inspection, shrimp in rearing tanks should be checked every day. If any symptom is noticed they should be brought to the pathology lap for further diagosis.

e) For the control of Largenidium and other fungal disease, the application of 0.01 mg/l malachite or treflan is recommended. For bacterial disease the application of 3 – 5 mg/l of antibiotic (Oxytetracycline, Furazolidon or Erythromycin) is used, and for Zoothamnium sp. By 25 – 50 mg/l formalin is widely used. However, the shrimp stock may be transferred to another tank to cut off the cycle of pathogenic parasites.

Table 1 Optimum Ranges of Water Quality for Rearing the Penaeid Shrimp Larvae

Parameter Optimum Preferable

Temperatures 280 C – 320C 300C

Salinity 28 – 32 ppt 30 ppt

TurbiditySuspended solids 0 – 100 mg/l 0 – 10 mg/l

Total solids 0 – 1000 mg/l 0 – 100 mg/l

Cont.

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Parameter Optimum Preferable

pH 6.5 – 8.5 7 – 8

Dissolved oxygen 4 – 10 mg/l 8 – 10 mg/l

Reactive phosphate content 10 – 100 g/l 10 g/l

Unionized ammonia (NH3) 0 – 0.1 mg/l 0 mg/l

Ionized ammonia (NH+4) 0 – 1.5 mg/l 0 mg/l

BOD 0 – 4 mg/l 0 mg/l

COD 0 – 3 mg/l 0 mg/l

Nitrate (NO2) 0 – 6 mg/l NO2-N/l 0-0.5 mg NO2-N/l

Nitrite (NO3) 0 – 200 mg/l NO3 – N/l 0-50 mg NO3-N/l

Toxic substances/metals:Oil 0 – 5 mg/l 0 mg/l

Arsenic 0 – 0.03 mg/l 0 mg/l

Copper 0 – 0.01 mg/l 0 mg/l

Cyanide 0 – 0.001 mg/l 0 mg/l

Lead 0 – 0.03 mg/l 0 mg/l

Potassium 50 – 400 mg/l 50 mg/l

Pesticide Nil Nil

10. HARVESTING AND HANDLING

10.1 Harvesting

Decrease the water level to 20 – 30 cm before opening the outlet and letting the larvae flow out with the water. The rapid flow of water may harm the larvae. The larvae can be collected by using a net bag at the outlet and transferred to 0.5 – 1 m3 tanks which are

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equipped with strong aeration system for stocking before packing. The stocking density in this tank should be about 0.5 – 1 million fry/m3.

10.2 Sampling Method

The number of fry can be estimated by many methods (Roengphanich, 1986).

a. By estimating with naked eyes : -The density of larvae in the sampling container can be compared to the number of the larvae with known amount.

b. By weight : - counting the number of larvae with known weight, then weigh the total larvae and calculate the total number.

c. By using the strainer and fill it to the top with larvae, or to any larvae and marked the level. Count the total number of larvae in the strainer. Collect the larvae by filling the strainer to the top or up to the mark level. Record the number of times needed to remove all the larvae from the tank and multiply by the known number to obtain the total number of larvae.

10.3 Packing

The shrimp seed are placed in polyethylene bag ( 28” x 32”). Each bag contains 5 liters of filled seawater. The number of seed is about 2,000 – 2,500 post larvae per bag, depending on the size and transportation time. Oxygen is filled into the bag before sealing.

10.4 Handling

Handling of the larvae can be done by the following method;

a. For short distances transportation; the fry are placed in the tank with aerated seawater or in the polyethylene bags ( 28” x 32”) in oxygenated seawater (20 – 240C) and transported by bus in the period of 8 – 12 hr.

b. For long distance transportation; the fry are usually placed in the polyethylene bags ( 28” x 32”) in oxygenated seawater (20 – 240C) and the bags are placed into the plastic bags or foam boxes and then transported by bus or by air. In order to control the temperature and to prevent cannibalism, small bags of ice and Artimia are usually added in the box.

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BIBLIOGRAPHY

Cook, Hil. And Murphy, MA 1966. Rearing Penaeid Shrimp from Eggs to Post Larvae. Proc. Conf. Southeast Assoc. Game Comm. 19 : 283 – 288

Hudinaga, M. 1942. Reproduction, Development and Rearing of Penaeus japonicus Bate. Jap. J. Zool., 10:305-393

Kongneo, H. 1994 How Thailand Become the Largest Producer of Cultured Shrimp in the Word. ASEAN – EEC Aquaculture Development and Coordination Programme, Bangkok, Thailand 22 p.

Kungvankij, P. 1982 The Design and Operation of Shrimp Hatcheries in Thailand. Working Party on Small-scale Shrimp/prawn Hatcheries in Southeast Asia, Semarang, Central Java, Indonesia, Technical Report pp. 117 – 120

Primavera, J.H. 1982 Development of Broodstock for Small-scale Hatchery (with particular reference to Penaeus monodon). Working Party on Small-scale Shrimp/prawn Hatcheries in Southeast Asia, Semarang, Central Java, Indonesia. Technical Report. Pp. 71 – 76.

Roengphanich, N. 1986 Breeding and Nursing of Penaeid Shrimp. Southeast Asian Fisheries Development Central. SFIS Extensive Manual Series no. 39 31 p.

Sorgeloos, P., Bossuyt, E., Larvae, E., Baeza-Measa, M., and Persoone, G. 1997. Decapsulation or Artimia cysts: a Shrimp Technique for the Improvement of Use of Brine Shrimp in Aquaculture, Aquaculture, 12, 311 p.

Tail, Y., Primavera, J.H. and Llobrera, J.A. 1985 Proceedings of the First International Conference on the Culture of Penaeid Prawns/shrimp. Aquaculture Development Southeast Asian Fisheries Development Center, Iloilo, Philippines. 197 p.,

Tiensongrusmee. B. 1982 Design of Small-scale Prawn/shrimp Hatchery Suitable for Developing countries in Southeast Asia; 1. Based on a Model Design for a Freshwater Prawn Hatchery used by Majuikan in Malaysia. Working Party on Small-scale Shrimp/prawn Hatcheries in Southeast Asia, Semarang, Central Java, Indonesia. Technical Report. Pp. 45-52

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