Status of Grouper Breeding and Culture in Thailand

R. Yashiro[1]

Abstract

Epinephelus malabaricus, E. coioides, E. tauvina, E. salmonoides, E. lanceolatus, E. fuscoguttatus, Lutjanus argentimaculatus, L. johnii, Plectropomus maculatus, and Cromileptes altivelis are being cultured for local and overseas consumption using seed supply mainly from the wild. Small traps, push net, shelter trap, and gill netting are used for catching fish juveniles. Only Lates calcarifer seeds are supplied by government and private hatcheries. Hatcheries produce occasionally Epinephelus malabaricus, E. coiodes, E. tauvina, E. salmonoides, and Lutjanus argentimaculatus due to improper management of broodstock and nursing. The breeding and grow-out of groupers (Epinephelus spp.) in Thailand were attempted but there are constraints. The cage and earthen pond culture systems for these groupers including aspects of culture such as stocking density, feed, feeding of grouper, are reviewed and discussed. The fish (mainly alive) are exported to Malaysia, Singapore, Taiwan, and Hong Kong at 5.6 to 21.6 $US/fish (0.5 to 1.3 kg), depending on the season. Ninety percent of the fish farmers culture grouper in cage which set in natural sea-water along the coastal areas at the southern and eastern part of Thailand. Recently about 10-20% of shrimp ponds are being converted to fish culture and may continue to increase. Environmental pollution and diseases are causes of loss of profit in fish culture and farming. Diseases of culturing marine fish are discussed separately.

Introduction

More than 40 species of groupers were reported (Sirimontrapom, 1994) in Thai waters. Many of these species (Epinephelus spp., Plectropomus spp., and Cromileptes sp.) are cultured in Thailand for some time now. They are suitable culture species because they are easy to grow and fast-growing. Furthermore, the groupers have desirable white, tender, tasty meat that Asians find desirable. These species are cultured in cages along the coastal areas in the eastern and southern Thailand. This is in response to the high demand for these fishes in domestic and international markets.

The cage culture of groupers followed the decline of the shrimp-farming industry. Since 1990, many shrimp farms are forced to stop their operations because of diseases and environmental problems. The shrimp farmers began to culture brackishwater fish (seabass) and marine fishes (groupers) in the former shrimp ponds. The main supply of grouper seeds is from the wild.

From this beginning, grouper culture is progressing in Thailand. The techniques, status, and constraints of breeding, nursing and grow-out techniques of grouper, Epinephelus coioides and E. malabaricus, that are presently produced and cultured in Thailand, are reported in this paper. Aside from these groupers, other marine fishes are also cultured in Thailand. The production of major species, based on trends over the past 5 years, major culture system types (Figure 2) and geographical location of culture systems are reported in this paper (Table 3).

Cultured Species

Eight species of groupers are cultured along the coast of Thailand. The Malabar grouper, Epinephelus malabaricus, and the orange-spotted grouper, E. coioides, are the two major species that are being cultured because of its economic importance. The six minor species also being cultured are the greasy grouper, E. tauvina, the giant grouper, E. lanceolatus, the areolate grouper, E. areolatus, the brown-marbled grouper, E. fuscoguttatus, the spotted coral grouper, Plectropomus maculatus, and humpback grouper, Cromileptes altivelis. Aside from these groupers, the seabass, Lates calcarifer, and the red snapper, Lutjanus argentimaculatus are major species of marine fishes being cultured in Thailand. These fishes are primarily inhabitants of shallow coastal reefs, although some species range into deeper water of above 100 m.

Overview

Culturing of grouper

Groupers are sluggish fish always found rest quietly among the rocks or hiding among the corals. They like to live in waters with salinity ranging from 12 to 30 ppt and temperature range from 22°C to 28°C. The fish farmers culture groupers both in cages and earthen ponds but most (about 90%) of farmers culture them in cages that are set in seawater. The cage culture of grouper is being conducted at provinces along the coastal areas at the southern and eastern part of Thailand, i.e., Suratthani, Chumporn, Nakhonsri-thamarat, Songkhla, Pattani, Satul, Krabi, Trang, Phang-nga, Phuket, Chachengsao, Rayong, Chantaburi, and Trard. The pond culturing are found in some provinces as Pachaburi, Suratthani, Nakhonsri-thamarat, Songkhla, Satul, Chantaburi and Trard. The majority of grouper seeds for culturing were obtained from the wild, because seeds from hatchery were limited, due to unstable seed production and nursing techniques (Chen et al., 1977; Ruangpanit et al., 1988;Sakares and Sukbantaung, 1987).

Marketing and trading of live fish

Grouper seed from the hatchery go directly to the fish-farmers that will then be cultured either in cages or in ponds. On the other hand, natural seeds go through the middleman before these reach the farmer to culture and grow. When the fish has attained marketable sizes, they are supplied direct to fine domestic consumers or export to Hong Kong, Singapore, Taiwan, and Japan. The flow charts of trading and prices of grouper and other marine fishes produced from natural seeds and from hatchery-produced seeds are in Appendix 1 and 2.

Grouper breeding and larval rearing

Breeding

The research on breeding of groupers has begun more than 20 years ago. The first success in mass propagation of grouper seeds was achieved in 1988 at Tamano association in Japan. The sea-farming association produced over 100,000 fry of Epinephelus akaara (Fugunaka et al. 1990). In 1989, the same grouper was reported to produce as high as 403,000 fry (Murayama et al., 1993). In Thailand, attempts breeding of other species of groupers, such as E. tauvina, E. salmonoides, E. malabaricus, and E. suillus, were not as successful (Julavitayanukul et al., 1985; Sakaras and Kumpang, 1986; Rattanachot and Ningnoi, 1986; Hunsopa et al., 1990), Kungvankij et al., 1986; Ruangpanit et al., 1988; Doi et al., 1991). Aside from breeding, induction of spawning and seed production by environmental or water management method and hormonal injection were attempted by these researchers. The fry production from these species is still under 100,000. Eventually, mass propagation of grouper seeds at National Institute of Coastal Aquaculture was attained during 1991-1993 until present but production is still inconsistent.

Broodstock preparation and breeding

Grouper broodstock were cultured in net-cage 5x5x2.5m at Nu Island where the water salinity is around 28-34 ppt throughout the year. They were transferred to the 150-tonne, round-shaped, concrete ponds during September each year. The physico-chemical characteristics of the concrete ponds are maintained at 30-31 ppt and 28-30°C and by changing 50-80% of the water daily. The broodstock was fed with fresh sardines every day at 1-2% of their body weight. Vitamins and minerals were added into the diet by embedding capsules of these into the sardine before feeding. In particular, Vitamin E (4,000 mg/kg), Vitamin C, fish oil, and Premix 0.3 g/kg are added for better growth performance.

Table 1. Number of grouper brood stock used in breeding 1991-1993

Year	Male	Weight (kg)	Female	Weight(kg)	Remark
1991	15	11-15	15	5-6.5	30 Fish/tank
1992	20	10-15	30	3.5-7.5
1993	9	9.5-12	21	4.5-7.5

Source: Ruangpanit et al., 1993a

The grouper-breeding season in the wild is during October to March each year and the females lay eggs at night from 2100-2400 H. To induce breeding and spawning in the hatchery in 1991 to 1993, male broodstock weighing 9.5-15.0 kg and female 3.5-7.5 kg were chosen and were stocked in the spawning tank at the ratio of 1:1 or 1:2 male:female (Table 1). The groupers were subjected to two methods, namely, by water manipulation and by hormone injection. Details of the procedure are summarised as follows:

· water manipulation: 80% of water were changed 5 days before full moon or new moon. New water was added continuously to allow water overflow until about 80 % of water have been replaced. Grouper broodstock stimulated by water manipulation laid eggs 1-2 days before full moon or new moon. The females laid eggs 2-3 years for an average of 4-10 days each time. A better hatching rate was obtained by this method. The broodstock can be injected later on with hormones for further rematuration and spawning. (As this does not use hormones, it is considered in this paper a “natural spawning” (Table 2)).

· hormone injection: Puberogen, the commercially available hormone, was used at dosages of 100 IU/kg and 50 IU/kg body weight of female and male broodstock, respectively. The broodstock are first checked for suitability of this procedure. A sample of the female oocyte was examined. If the oocyte size is over 400 micrometers, it is considered suitable for inducing maturation by this hormone. The male should have white milt flowing when the abdominal part is gently pressed. The hormone injection should be given 2-5 days before the new moon. The broodstock release their eggs 3-9 days after hormone injection for 5-16 days continuously.

The results of these two methods of breeding induction and spawning are different. Egg production is lower by water manipulation than with hormones but hatching rates, survival rates, and spawning frequency are slightly higher (Table 2). The number of spawning days was from 10-23 days by water manipulation while, for hormonal induction, ranged from 7-33 days.

Table 2. Number of eggs, hatching rates of grouper, and other aspects of spawning under two conditions during 1991-1996 (NS, natural spawning; HI, hormonal injection)

Year	Aspects
	Eggs (x10⁶)		Larvae (x10⁶⁾		Hatching rate (%)		Spawning (occurrence)		Spawning Duration (in days)
	NS	HI	NS	HI	NS	HI	NS	HI	NS	HI
1991	4.16	11.97	1.81	4.76	43.51	39.76	3	1	23	10
1992		32.37		11.16		34.47		3		33
1993	6.75	7.02	3.05	2.2	45.19	31.33	2	1	10	9
1994	-	-	-	-	-	-	-	-	-	-
1995	-	-	-	-	-	-	-	-	-	-
1996	-	4.23	-	1.37	-	32.47	-	1	-	7
Total	10.91	55.59	4.86	19.47			5	6	33	59
					44.55	35.06

Hatching

Grouper eggs are 800 to 900 microns and are of the floating type. The floating eggs are collected, the following morning after induced-spawning procedures, washed, and placed into the funnel-shaped fibre glass tank with a capacity of 500 li. The water used for hatching has salinity of 30 to 3l ppt and pre-treated with chlorine or calcium hydrochloride at 20 ppm. The eggs are kept in the tank with the density of 500-1,000/li. The fertilised eggs hatch within 17-19 hours at 26 to 29°C and the larvae were then transferred to the nursing pond.

Larval Rearing

Preparation of nursing pond and water management

Concrete tanks with the volume of 25 tonnes and dimension of 4x6x1.5m were used for larval rearing. The pre-treated water, used for hatching was re-used to fill half of the tank. Aeration was used and water temperature was kept at 27-30°C. During nursing, green water (Chlorella sp.), about 1 ton was poured into the tank everyday, until the tank filled up.

Water is changed throughout the nursing period. Ten to 20% of water was changed every day. At Day 20, Day 30, and Day 45 of nursing, the daily rate of water change was increased to 30%, 40% and 50%, respectively. The bottom cleaning was done everyday during Day 12 to Day 19 by siphoning out sediments and dirt and every 3-5 days after Day 20 or when fry start to school at the bottom of the tank. Later when the fry can start feeding on fresh feed and mixed pellets, the cleaning of the bottom of the tank was done every day.

Larval feeding

The mouth of larval groupers opens around 53 to 59 hrs after hatching and 6 hours later the fry begin feeding (Ruangpanit et al., 1993b). Thus, a variety of feeds are necessary. After Day 2 or the 48th hour, the fry are then fed daily with small rotifers (Brachionus plicatilis), that can pass through 125-micron mesh nets, at 10-15 individuals/ml, and the sea Chlorella at 1 ton. All sizes of rotifers will be added from the Day 6 to Day 29. During this time, fry were trained to feed on Artemia from Day l5 and supplemented with copepods and Moina. Adult Artemia was given at about Day 25. Artemia nauplii and adult should be enriched by emulsified fish liver oil at 50 ppm 19-22 hr before feeding or by commercially-enriched essential fatty acid (n3-HUFA 450mg/g) 200-300 ppt for 12-15 hr or 6-10 hr (Figure 1). Emulsified fish oil was prepared by using 50 ml of fish liver oil, 2 raw chicken eggs yolk, and 200-300 ml of water mixed in the blender for 2-3 minutes. This mixture was added to 1 tonne of seawater, composing of 200 li of green water (Chlorella sp.) and 800 li stocked with 100 Artemia/ml.

Age ( day)	5	15	20	30	40	45	50	55
1991-1992
Rotifer
Artemia nauplii
Copepod, Moina
Adult Artemia
Fish meat

1993
Rotifer
Artemia nauplii
Adult Artemia
Fish meat
Pellet feed

Source: Ruangpanit et al., 1993

Figure 1. Feeding scheme for grouper fry-rearing

Nursing management

Cannibalism in groupers is high at Day 35 to Day 40. Shelters must be put for increase survival rates of fingerlings. PVC pipes with a diameter of 2" were cut into 30-50 cm and were grouped by 4-6 pieces to hang along the edges and corners in the tank. By removing the fingerlings found in the shelter pipes 2-3 times daily could do the “sizing” of fingerlings.

Sources and types of seed/fingerlings

1-2 cm seeds/fingerlings: Almost all grouper seeds are obtained from the wild because seed production from the hatchery is still insufficient and the supply is unstable. To catch fingerlings, fishermen place aggregating devices or traps made of dried twigs along channels in the mangrove areas and other brackish waters along the coast. Every 2-3 hours or longer, these traps are lifted up and fingerlings are collected with scoop nets and then transported to the middle man or broker who sells it to the fish-farmers. Another procedure used by some fishermen is the gill net with a small mesh size (0.5-1.0 cm). The gill net block is placed across the known path of passing grouper fingerlings. The fingerlings are then collected by lifting the net and scooped up. The former method always cause mass mortality of fingerings when nursing due to the stress during trapping and transportation. This method is becoming more popular because it can catch more fingerlings compared to the gill-netting method. Push nets are also used to capture the fingerlings.

2.5-10 cm juveniles: Juveniles of this size are collected mainly with small fish traps locally called ‘sai’ of ‘lob’ (20x40x20cm) or with round traps with diameter of 20 cm and length 20-25 cm. Juveniles of giant grouper are caught by bigger traps (40x60x40 cm) or even bigger in some area as Pang-nga and Phuket. The frame of these traps are made of bamboo or mangrove branches and fixed with nylon net or plastic screen mesh size of 1-2 cm. The traps are set every evening at the brackish water or salt-water canal in mangrove areas or hidden in the reef area. Fishermen retrieve their traps the following morning or a few days after the deployment of the traps, depending on their sense of water currents and lunar cycles. Gill nets are also used for catching fish juveniles of this size range in some areas.

Grouper Culture Systems

Fingerling to juvenile

Grouper fingerling size of 1.0 to 2.5 cm from wild and from fish hatchery mostly are nursed in concrete tank, nylon net cage and earthen pond up to 8.0 to 12.0 cm, then transferred to fish cages or earthen pond for grow-out to marketable size.

Fingerling nursing in concrete tank. Nursing of groupers can be done in 1 m³ round tank or 5 to 30-t round or rectangular-shaped concrete tanks. They were stocked with fingerlings of 4.3 cm at 15 to 50 individuals/m² and nursed up to 9 to 10 cm for 60 days. They were fed with fresh fish and wet or moist and dry pellets (Panbanpeaw and Sakaras, 1990) to satiation once or twice per day. In high-density stocking rates, concrete blocks are used as shelters. Grading or sizing is needed for homogenous growth and for minimising loss due to cannibalism.

Fingerling nursing in nylon net cage: Nursing fingerling grouper in net-cages (1x1x1.5 m³) is better than in concrete ponds because stocking density is higher and growth rate is better (Chulawitayanukul et al., 1988). Stock fingerlings of 5.7-cm (3.1 g) at 300 to 500 individuals/m² fed with trash fish for 75 days can produce juveniles of 14.1 cm (49.9 gm) with 91.1 % survival in salinity 15.2 ppt.

Fingerling nursing in earthen pond: Earthen ponds measuring 800 m² up to 3,200 m² are always used for nursing grouper fingerling. These ponds are stocked at 25 to 100 individuals/m² and fed with trash fish. At about 45 to 60 days, individuals attain the size of 10 to 15 cm. These juveniles are partially or totally harvested by seine and sold or transferred to be cultured in net-cages and earthen ponds. Survival rates are rather low compared to the other two methods above but fishermen do not want to spend time in sizing individuals for culture.

Cage culture

Location of grouper cage culture

Majority of fish farmers likes to culture groupers and other marine fishes in cages because of convenience and lower cost of investment compared to culture in ponds. Cage culture is versatile as it can be operated in brackishwater area near mouth of the river, along the coast, or on islands in open sea. The cage culture system also eliminates the problems of water management that are faced in pond-culture. The cage culture of seabass were demonstrated by the Department of Fisheries under the Bay of Banjul Project (BOB) in the southern part of Thailand and became very popular because of the above advantages. Most of fish-cages are located in the coastal provinces in southern Thailand, i. e., Trung, Pang-nga, Krabi, Satul, Nakornsri-tummarat, Songkhla, Phuket, and Ranong and some along the eastern coast of Thai Gulf, i. e. Chachoengsao, Rayong Chartaburi, and Trard (Table 3).

Table 3. Location, total numbers of cages, and number of for grouper culture in Thailand

Province	Area (rai)	Area (ha)	No. of cage	Grouper cage
Chumporn	2.25	0.36	147	79
Suratthanee	836.7	133.87	357	-
Nakornsrithamarat	356.7	57.07	130	102
Patalung	129.01	20.64	520	-
Ranong	36.56	5.85	834	435
Phuket	9.28	1.48	600	503
Phang-nga	28.37	4.54	3,979	2,055
Krabi	34.6	5.51	542	270
Trang	17.18	2.75	559	475
Satul	164.66	26.35	1,970	1,734
Pattani	51.38	8.22	1,553	2
Naratiwat	8.45	1.35	1,392	64
Songkhla	371.67	59.47	1,220	<10
Chachuangsoa	-	-	2,000	-
Rayong	-	-	10	10
Chantaburi	-	-	50
Trard	-	-	60	5

Design and construction of fish-cage

There are 2 types of fish-cages, namely, the fixed and floating cages. Both cages are either square or rectangular and comes in several sizes, e. g., 1.5xl.5x2m³, 2x2x2.5m³, 3x3x2m³, 4x4x2m³, 5x5x2m³, and 10x10x3m³, etc. The type of cage used by fishermen depends on the water depth and level of investment.

Fixed cage - This type of fish-cage has the nets fixed to strong and stable posts, so the cage cannot move up and down along with tidal movement. The areas suitable for this cage type should be not deeper than 2.5 m and the tidal difference between highest and lowest tidal levels should be about 50 to 60 cm. This type is popular in the eastern provinces as Rayong Chantaburi, Trard and some in the southern provinces as Chumporn Surattani, Songkhla, and Pattani. A variation of this type is set at Aow Makarmpom, Klang district, and Rayong province. The fish-cage has a frame made of steel bars and fixed with nylon attached to it. It is set in deeper areas and is completely submerged during high tide. Feeding of fingerlings is done through the PVC pipe with a diameter of 10.0 cm.

Floating cage - This type is suitable for culturing in waters deeper than 2 m and with tidal range of more than 1 m. The net is tied within the raft or floater made of bamboo or styrofoam and have steel bars to fix and reinforce the raft. This type is suitable for fish-cages that face to the open sea such as in Satul, Trung, Krabi, Ranong, and Pang-nga. The floating net-cage can be constructed into 2 styles, with frame and without frame. The cage with frame is the one that is popular to fishermen.

Cage with frame The frame is either steel bars with a diameter of 1 inch or wood of bigger diameter. The frame will help fix and reinforce the net cage therefore allow good circulation of water through the cage.

Frameless cage - The top of the net is tied to the float and the bottom is held down with sinkers at every corner. Since this cage is frameless, the shape of this type of net-cage changes according to the velocity of the current. This type is suitable for temporary stocking of fingerlings because the water circulation in the cage is poor.

Besides the construction of cages, several aspects are considered in the cage culture of groupers. The mesh sizes appropriate for nursery is 1 to 2 cm and for grow-out at 5 to 7 cm. The materials for the raft and posts for fixing the cage should be inexpensive, strong enough to stand wind and wave action, easy to clean, and can be transported to another place. The design of raft should convenient for culture and the net should have no dead corners. The net-cage is fixed to the floating raft with a distance of at least 30-cm from the water surface level to allow circulation. The distance of 1 to 3 m between cages and 3 to 5 m between rows of cage are recommended also for good water circulation (Tipchid et al., 1984; DOF, 1986).

Stocking density and production

The density of stocking has been variable over the years. In traditional cage culture for groupers, the stocking density 15 inds/m³ (DOF, 1980) but recently fingerlings were stocked at various densities from 30-125 inds/m² (Table 4).

Table 4. Examples of stocking densities and yield/m² of grouper in grow-out net cages

Fish size (cm)	Fish size (gm)	Stocking Density (inds./m²)	Average Yield (kg/m²)	References
-	61.2, 103.4, 149.4	30,45,60	16.8, 23.8, 29.7/ 6 months	Sakaras & Sukbuntaung, 1985 (cage size1x1x1.5m³)
10-15	20,30,60	60,75,90	27.8, 33.9, 37.9/ 6 months	Sakaras & Kumpang, 1987a (cage size 1x11x1.5m³)
15-30	80-300	12.5	7.5-9.4/6 months	Priyiwatee, 1988 (cage size 4x4x2m³)
16.2	83.7	75	31.8/6 months	Sakaras & Kumpang, 1988 (cage size 2x3x1.5m³)
-	126.3	40, 50, 60	13.4, 15.5, 15.6/ 5 months	Chulawitayanukul et al., 1989 (cage size 1.5x3x1.5m³)
12.3-16.9	628.6-67.1	75,100,125	31.6, 44.5, 53.7/ 6 months	Sakaras et al., 1990 (cage size 1x1x1.5m³)

Source: Ruangpanit and Yashiro (1994)

The appropriate stocking density of grouper cage culture in brackishwater (21-25 ppt, 29-30°C, pH 7.33, D.O. 5-6 mg/l with water flow 300-500 m³/hr), based of dissolved oxygen budget (Nabhitaphata et al., 1988). The lower optimum density was 58 inds/m³ or 75 inds/m² with possible stocking limit of 351 inds/m³ or 457 inds/m² for fish up to 500 gm, and 31 inds/m³ or 40 inds/m² for fish up to 1.2 kg with possible limit of 187 inds/m³or 244 inds/m². At high stocking densities of 100 and 125 inds/m², with addition of artificial shelters, the production/cage was higher but feed conversion rate (FCR) was lower (Sakaras et al., 1990; Table 4). However, there was no statistical difference on growth, survival rate, and fitness of fishes cultured in optimum stocking density (75 inds/m²) compared with those cultured at higher stocking densities (100 to 125 inds/m²). As stocking density increases, yield increases but the FCR decreases. Thus, optimum-stocking density is 75 inds/m² and the best stocking density is at 90 inds/m². At the best stocking rate, production rate of 37.9 kg/m² and food conversion rate of 6.78 kg/fish was observed (Table 5).

Table 5. Grouper cage culture at various stocking densities (6 months) which showed no difference on growth and survival rate but production yields were higher with increasing stocking density (Source: Ruangpanit and Yashiro, 1994)

	Stocking density (inds/m²⁾
	30^*	45^*	60^*	75^**	90^**	100^***	125^***
Final growth (gm)	601.9	547.6	508.8	473.9	448.3	467.7	443.1
Survival rate (%)	93.3	97.0	96.7	95.5	93.7	95.7	96.8
Yield (kg/m²)	16.8	23.9	29.7	33.9	37.9	44.5	53.7
FCR: kg fish	8.82	-	-	6.33	6.78	5.2	4.8

^*Sakaras and Sukbuntaung, 1985, ^**Sakaras and Kumpang, 1987a, ^**Sakaras et al.; 1990

This finding on the relationship of stocking rate and feed conversion rate is very useful for an economically viable cage culture operation given the culture site, soil substratum, and water quality. To illustrate this, an economic analysis of stocking rate and production was conducted for grouper (E. malabaricus) cage culture at Tuppud district, Phang-nga province (Priyawatee, 1988). A total of 420 cages were operated by 60 families (3 have >10 cages, 2 have 5 to 9 cages and 55 families have 1 to 4 cages). The financial investment involves expenses on fixed costs for infrastructure and variable costs on operational costs. The fixed costs for 4 cages was estimated 12,000 Baht (480 US$), with depreciation cost at 4,000 Baht (160 US)/year (aging of equipment over 3 years) for structures (cage construction, materials, raft, etc.). The variable cost is 41,000 Baht (1,640 US) for operational cost (fish, feed and wage/day 6 months). Therefore, if the fixed cost of investment/cage was excluded, the cost of operation will be 10,250 Baht (US$450; may be plus 25-30% in 1994). The farmers produced groupers weighing 400 to 800 g at 40 to 60 t/y at an average selling price of 220[2] Baht (US$8.8/kg). This level of production and income could increase if stocking density is increased 6 times more from 12.5 inds/m² to the optimum stocking density of 75 inds/m².

Fingerling to juvenile grouper

Cage culture management

Net-cage culture is labour-intensive. Sometimes, the net-cages are blocked by sediment since there are located in turbid waters, near mouths of rivers. Molluscs and seaweed sometimes block the mesh of net-cages that are located in the open water. In addition, sediment and attached mollusc and seaweed increased weight of the net-cages, resulting to partial closure of the mesh. These blockage and partial closure of mesh may cause diseases or parasite infestation on the cultured fishes because of bad water circulation through and in the net. Therefore, it is necessary to change nets used for culture to allow time to clean and dry the netting material every 1 to 2 months, depending on the rate of accumulation of unwanted dirt. Raft, sinker, and float also have to be checked regularly. In high stocking density, sometimes partial harvesting is recommended to eliminate the loss due to the cannibalistic habit of groupers. Stocking fishes at various times and rotation of harvesting is also practised to ensure continuous income for small fish-farmers.

Water quality

Metabolic wastes from cultured fishes are removed by water passing through the nets. Thus, the water quality in net-cages depends on the current in the culture area. If the current is weak, metabolic wastes accumulate at the bottom of the nets, and the water quality inside the nets is poorer than that outside. If the tidal current is strong or heavy fresh-water run-off during rainy seasons, there are no significant differences in the water quality parameters among areas and between inside and outside the cages (Table 6 and 7; Songsangjinda et al., 1993).

Table 6: Average water quality from grouper cage culture area of Khlong Pakbara, Langu district, Satun province during the rainy season in October 6, and 19, 1993. area 1: outside cage area (n=5), area 2: net cage under 3 years old (n=3) and area 3: net cage over 3 years old (n=4). None of the differences were significant (p>0.05)

	Average water quality
Parameters	Outside cage area			net cage under 3 years old			net cage over 3 years old
	range	average	SD	range	Average	SD	range	average	SD
Dissolved Oxygen (mg/l)	4.72-5.19	4.99	0.22	4.55-4.64	4.59	0.05	4.77-5.33	5.13	0.25
Oxidation Reduction Potential (mv)	183-215	200	12	177-188	182	6	171-219	198	22
Nitrite-nitrogen (mg/l)	0.002-0.010	0.05	0.003	0.002-0.003	0.0027	0.0006	0.002-0.006	0.005	0.002
Nitrate-nitrogen (mg/l)	0.008-0.050	0.025	0.017	0.010-0.023	0.016	0.007	0.009-0.033	0.024	0.011
Total ammonia -nitrogen (mg/l)	0.07-0.077	0.036	0.026	0.004-0.026	0.018	0.012	0-0.45	0.019	0.022
Inorganic nitrogen (mg/l)	0.020-0.111	0.066	0.039	0.030-0.042	0.037	0.006	0.013-0.083	0.047	0.032
Organic nitrogen (mg/l)	0.453-1.039	0.75	0.284	0.314-0.836	0.598	0.264	0.360-0.922	0.609	0.285
Total nitrogen (mg/l)	0.531-1.071	0.818	0.255	0.535-0.866	0.635	0.260	0.389-0.985	0.656	0.281
Reactive phosporus (mg/l)	0-0.030	0.012	0.012	0-0.005	0.002	0.003	0-0.014	0.009	0.006
Total phosporus (mg/l)	0.030-0.082	0.052	0.022	0.031-0.043	0.035	0.007	0-0.057	0.030	0.023

(Songsangjinda et al., 1993)

Table 7: Average sediment quality from grouper cage culture area of Khlong Pakbara, Langu district, Satun province during the rainy season in October 6, and 19, 1993. area 1: outside cage area (n=5), area 2: net cage under 3 years old (n=3) and area 3: net cage over 3 years old (n=4). All the average values are significantly different in each row (p<0.05)

	Average water quality
Parameters	Outside cage area			Net cage under 3 years old			Net cage over 3 years old
	range	average	SD	Range	average	SD	Range	average	SD
Nitrite-nitrogen	0.074-0.096	0.082	0.008	0.057-0.314	0.149	0.143	0.086-0.778	0.288	0.330
Nitrate-nitrogen	0.166-0.489	0.305	0.117	0.172-0.356	0.290	0.102	0.195-2.554	0.930	9.11
Total ammonia-nitrogen	2.03-3.16	2.64	0.48	2.11-5.81	3.80	1.87	3.12-36.33	12.62	15.87
Inorganic nitrogen	2.27-3.51	3.02	0.52	2.36-6.48	4.24	2.08	3.41-39.66	13.84	17.30
Organic nitrogen	66.92-217.4	133.36	60.65	147.89-254.19	206.20	53.9	426.9-1023.4	704.87	245.93
Total nitrogen	70.37-220.57	136.39	60.72	150.25-260.67	210.44	55.88	430.3-1030.9	718.72	245.58
Reactive phosphorus	0.196-0.409	0.343	0.087	0.87-1.74	1.24	0.45	2.46-12.99	5.19	5.20
Total phosphorus	6.75-21.0	13.93	6.62	7.37-80.62	32.96	41.32	62.75-78.12	72.66	7.05
Ignition loss (%)	0.59-2.10	0.78	0.21	0.54-3.37	1.83	1.43	4.13-16.21	8.04	5.65
Total sulphide	0-0.38	0.19	0.17	0-3.63	1.74	1.83	0.028-19.98	9.55	8.16

(Songsangjinda et al., 1993)

Figure 2. Production of Grouper (Epinephelus malabaricus) juvenile age 50-55 days during 1991-1996

Pond Culture

Pond construction and layout

Seabass and grouper culture ponds are constructed similarly as the coastal shrimp pond. The site should be carefully selected as mentioned above. The size of seabass rearing pond in the past was recommended to be at least 0.4 to 3.0 ha (4,160 to 31,200 m²) and 50 to 60 cm deep. Smaller ponds are costly and inhibit the growth of fishes (Sirikul, 1982). Later, the Department of Fisheries (1993) recommended that fish ponds should have area of about 800 to 1600 m² and depth of 1.5 to 2.0 m deep because bigger ponds will be under-utilised due insufficient number of juvenile fish fingerlings.

The fishpond should have two water gates for the in-flow and out-flow of water. The pond bottom should slope slightly toward the 30 to 40 cm deep passageway and deeper than the pond to facilitate drainage. Some farms use PVC pipe (16-20 cm in diameter) to pass through the dike for this purpose. The dike should be wide (3 to 6 m wide) for working on and compacted well to be strong.

Fishpond management

Pond preparation has to be done before the culture of any fish. The pond is flooded-out 2 to 3 times before cleaning by draining and pumping out all water at low tide. The mud and other dirt are removed, leaving the clear bottom exposed to sunlight for 2 to 3 days to 1 week. Lime is then used to disinfect and kill some pests that still left on the surface (0.06-0.12kg/m²). The pond is filled at high tide and then fertilised with chemical or organic fertilisers for good natural feed (plankton) to bloom before juveniles are released to the pond. In the case of big fingerlings (200-300 g), fertilising the pond may be omitted. During culture, 40% to 70% of water change from the natural source should be done everyday to maintain good water quality. A water reservoir is now necessary for fishpond culture as well as shrimp culture. At least 30% of total area should be a reservoir for stocking of water before pumping to the culture ponds. This practice can prevent infection by parasites and diseases.

Nutrition, Feed, and Feeding

Majority of grouper culture operations in Thailand use trash fish or fresh fish as feed, i. e., the yellow-striped trevally (Selaroides leptolepis), sardines or fringe-scale sardinella (Sardinella fimbriata), and round scad (Decapterus russelli), etc. These fishes have high protein level and are suitable for cannibalistic species. The protein level of 50% was reported to give maximum weight gain for grouper, Epinephelus tauvina (Teng et al., 1977; Sukhawongs et al., 1978).

The feeds and feeding schedule for some groupers are similar to seabasses (Chua and Teng, 1978; Sakaras, 1990; Boonyaratpalin et al., 1993b; Wannagowat, 1994). Like seabass, E. tauvina fed once every 2 days will greatly enhance maximum feed intake and efficient utilisation of fish food. The formulated feed for seabass and vitamin C were utilised successfully by E. malabaricus. Commercially extruded feed with slow sinking rate is available in some Asian countries at present. This diet contains more than 73 % and 6 % crude protein and fat, respectively, and it has less than 16 % ash, 3% fibre, and 12 % moisture (Boonyaratpalin, 1993).

The feeding rate and food conversion rate (FCV) was better with dry pellets than using fresh fish and wet formulated feed in juvenile groupers (31.7-71.6 g; Panbankaew and Sakaras, 1990). The feeding rates were 2.99 %, 11.11%, and 8.81 % for dry pellet, wet formulated feed, and fresh fish, respectively. The FCRs per kg were 1.22, 5.03, and 3.98. The FCR of trash fish for 6 months cage culture of grouper were reported as high as 8.82:1 at stocking densities of 30, 45, and 60 inds/m² (Sakaras and Sukbuntaung, 1985) and the lowest was 4.8:1 when stocking density was increased to 125 inds/m²(Sakaras et al., 1990).

Diseases and Parasites

Diseases

Diseases are one of the major causes of nursery and grow-out mortality posing the principal constraint in the future development of grouper and seabass cultures. About 10 years after the successful production of seabass seeds in 1974, many diseases have been reported in juveniles (> 200 g). Some fungal diseases were reported in freshwater seabass culture but not in brackishwater (Ruangpan, 1985). Various bacterial diseases including Aeromonas spp., Flexibacter spp., Vibrio spp., and Streptococcus spp. were identified from the sick fishes (Danayadol, 1984; Ruangpan, 1985; Direkbusarakom and Danayadol, 1987). Bacterial infection was followed by viral diseases in the lymph (lymphocystis) and kidney which is caused by unfresh trash fishes (Limsawan et al., 1983; Danayadol et al., 1984). Last year, 1993, a new viral disease occurred in the broodstock (5-7 kg) of seabass in southern Thailand (Danayadol et al., 1994). The fish is pale (no blood), lethargic, anorexic, and bloated with excess abdominal fluid. The sick fishes rest at the water surface and die within 2-3 days. The resulting mortality is about 60% of broodstock and this is a big loss to a hatchery. The present knowledge and experience on treatment of viral diseases of grouper and seabass are variable and fragmentary.

Parasites

Some parasites have reported to be the main cause of mortality in juveniles and sometimes in adult fishes. The ciliated protozoa are the most important parasites that cause high mortality in seabass cage culture (Ruangpan, 1985). These protozoa always attack 10 to 20-day fry and 2 to 3-month juvenile seabass. There are 5 groups of protozoa that are pathogenic:

1. Icthyopthirious and 2) Cryptocaryon, occurring in freshwater and brackishwater, respectively; these cause 'white spot' or 'ich' diseases - These protozoa will attach to the gill filaments and disturb the normal functions of the gills. The fish have to swim up to the surface and gasp for air sometimes. Some fish may scrape the net-cage or pond side and have wounds on the skin. Fishes attacked by these parasites will have small white spots on the skin first at the fins and along the body surface. In some cases, have fin rot or uncompleted scales, resulting to a weakened and anorexic fish. The fish sometimes becomes vulnerable to attack by bacteria and die soon.

3. Trichodina - This protozoon attacks the gills. The affected fish have pale gills and are covered with mucus. This protozoan always attacks fingerlings and juvenile fish.

Epistylis - This protozoon attacks seabass cultured in freshwater. With its stalk, this protozoon attaches itself to the skin, gills, and eyes.

Oodinim - This flagellated protozoon causes the yellowish velvet skin disease. When it attacks the gills, the gill filaments fuse together, swell, and appear dark-reddish.

A variety of non-protozoa also cause diseases and mortality to cultured fishes. The monogenic trematode worm always attacks the fingerlings and juveniles but occasionally only the adult. The worms attach to the gills and suck blood from host. Parasitic crustaceans sometimes cause more than 70 % mortality in small fish cage culture. The copepods Caligus sp. and Ergasilus sp. were reported to have attacked seabass during the beginning of the rainy season in Chantaburi, Rayong, Prjoubkinkhan, and Songkhla. The isopod, Aega sp., was also reported to be the cause of huge losses for cage culture during rainy season (Ruangpanit, 1985).

Environmental Considerations

Marine finfish culture could result to eutrophication. Marine fish farming create farm sediment, which consists of excess food and faeces, that accumulate in the substrate of a farm. After years of cage culture operation, the substratum beneath the cage gets worse due to the accumulation of organic wastes. High level of organic waste in sediment tends to increase a level of eutrophication and consumption of dissolved oxygen in the culture area (Aure and Stigebrandt, 1990).

Constraints

Grouper breeding and hatchery

The constraints in breeding and hatching groupers are outlined below:

1. Quality and manipulation of broodstock - Further studies on the quality of broodstock in terms of management and nutrition are necessary in order to get good quality eggs and sperms at the right time.

2. Hatching techniques - The batch hatching method gave the lower hatching rate than the flow- through method but was more convenient (Ruangpanit et al., 1993b) and therefore is still use in most fish hatcheries. A more efficient hatching procedure has to be developed.

3. Egg collection technique - Fertilised eggs of grouper which float type were collected the next morning which are sometimes exposed to too much sun light. This technique may cause low hatching rate or alter the quality of the larvae.

4. Nutritional problems - Broodstock and fry nutrition still have many point to be research in order to get good quality fry and high survival rate. The mass mortality of the 20-day old fry was essential fatty acid deficiency (Ruangpanit et al., 1993b; Pechmanee et al., 1989; Maruyama et al. (1993). Dhert et al. (1991) reported that they could reduce the mortality rate grouper fry by adding adequate amounts of fatty acid into the feed.

5. Diseases problems - Various diseases, bacterial and viral, are still encountered during nursing and grow-out periods. Knowledge of diseases and treatment are needed to maintain good health of cultured fishes.

Grouper aquaculture

1. Seeds - Inconsistent supply of seeds from the hatchery to supply 3 government-owned grouper hatcheries and private hatcheries are operated, and only one government hatchery at NICA can mass-produce every year since 1990.

2. Feeds – Food supply is still dependent on fresh trash fish. A pellet feed for grouper should be developed.

3. Environmental management of the culture and adjacent areas – The management of the environment is still constraint as the drain-out of fish-farming add to the impacts of shrimp-farming and agriculture in the same area

4. Culture techniques – The culture techniques for both cages and ponds should be developed continuously in order to make culture grouper in a sustainable manner.

Literature Cited

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Chua, T. E. and S. K. Teng. 1982. Effect of food ration on growth, condition factor, food conversion efficiency, and net yield of estuary grouper, E. salmonoides (Maxwell), cultured in floating net cages. Aqua. 27: 273-283.

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Danayadol, Y. and S. Direkbusarakom. 1987. The diseases of Grouper (Epinephelus rnalabaricus, Bloch & Schneider) Contribution No. 1/1987. National Institute of Coastal Aquaculture Kao Saen Soi 1 Muang District, Songkhla Thailand. 6 pp. (in Thai).

Danayadol, Y. S. Direkbusarakom, and S. Boonyaratpalin. 1994. Epizootic haematopoietic necrosis, a new viral disease in seabass spawner, Lates calcarifer, cultured in Thailand. Tech. Paper No. 6/1994. National Institute of Coastal Aquaculture, Kao Saen Soi 1, Muang District, Songkhla, Thailand. 12 pp. (in Thai with English Abstract)

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Julavitayanukul, P. 1987. Study on effect of vitamin E for the development of grouper, Epinephelus tauvina, eggs. Review of the research on grouper culture conference 23-25 February 1987 at NICA, pp. 122-129.

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Kungvankij, P., L. B. Tiro. B. Pudadera, and I. O. Potestas. 1986. Induced spawning and larval rearing of grouper (Epinephelus salmonoides Maxwell), pp. 663-666. In J. L. Maclean, L B. Dizon, and L.V. Hosillos (eds). The first Asian Fisheries Forum. Asian Fisheries Society, Manila, Philippines.

Maruyama K., K. Nogami, Y. Yoshida, and K. Fukunaga. 1993. Hatchery technology on the breeding and seed production of red spotted grouper, Epinephelus akaara, in Japan. Japan Sea-Farming Association, Goto station, Tarnanuora, Nagasalii pp. 02-05.

Nabhitabhata, J., R. Prempiyawat, K. Klaokling, and S. Kabinrum. 1988. Estimation on optimum stocking density of grouper, Epinephelus tauvina (Forskål), in cages on basis of dissolved oxygen budget: Pang-rat river Rayong Brackishwater Fisheries Station Brackishwater Fisheries Division Department of Fisheries. 27 pp. (in Thai with English Abstract).

Panbanpaew, S., and W. Sakaras. 1990. Experiment on Sea Grouper, Epinephelus malabaricus, with dry pellet. Tech. Paper No. 38/1990. Rayong Brackishwater Fisheries Station, Brackishwater Fisheries Division Department of Fisheries. 17 pp.

Patarapinyo, W., K. Silapajam, and J. Nugranad. 1987. Experiment on rearing of seabass, Lates calcarifer (Bloch), in earthen pond. Tech. Paper No. 44/1987. Prachuabkhirikhan Brackishwater Fisheries Station, Brackishwater Fisheries Division, Department of Fisheries. 7 pp. (in Thai with English Abstract).

Pechmanee, T., M. Assavaaree, P. Bunliptanon, and P. Akkayanon. 1989. Possibility of using rotifer, Brachionus plicatilis, as food for early stage of grouper larvae, Epinephelus malabaricus. Pp. 109-112. Report of the Workshop Shrimp and Feed Development, Johore Bahru, Malaysia. 25-29, Oct. 1988. ASEAN/ST/89/GEN/11.

Ruangpan, L. 1985. Diseases and parasites found in seabass cage culture. Tech. Paper No. 1/85, January 1985. Coastal Aquaculture Research Sub-division, Brackishwater Fisheries Division, Department of Fisheries. 16 pp. (in Thai).

Ruangpanit, N. 1985. Final Report Besut Integrated Fisheries Development Project Malaysia, Tanjong Demong Hatchery-Besut, Malaysia. Consultant, FI: GCP/MAL/009/ CAN., pp11-17.

Ruangpanit, N. 1993. Technical manual for seed production of grouper, Epinephelus malabaricus. National Institute of Coastal Aquaculture, Songkhla, Department of Fisheries, Thailand. 46 pp.

Ruangpanit, N., P. Bunliptanon, T. Pechmanee, P. Arkayanont, and J. Vanakovat. 1988. Propagation of grouper, Epinephelus malabaricus, at National Institute of Coastal Aquaculture, Songkhla, Tech. Paper No. 5/1988, National Institute of Coastal Aquaculture, Songkhla, Departrnent of Fisheries, Thailand. 16 pp. (in Thai with English Abstract).

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Ruangpanit, N., R. Yashiro, P. Bunliptanon, and V. Vattanakul. 1993b. Hatching and biology of early stages of grouper, Epinephelus malabaricus. p.45-49. In: The Proceeding of Grouper culture, Nov. 30 - Dec. 1, 1993. National Institute of Coastal Aquaculture, Songkhla, Thailand and Japan International Cooperation Agency, 133 pp.

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Sakaras, W. and P. Kumpang. 1987b. Comparative study on growth and production of Seabass, Lates calcarifer (Bloch), Cultured in cages with freshwater and mixed diet. Tech. Paper No. 14/1987. Rayong Brackishwater Fisheries Station, Brackishwater Fisheries Division, Department of Fisheries. 14 pp (in Thai with English Abstract).

Sakaras, W. and P. Kumpang. 1988. Growth and production of brown spotted grouper, Epinephelus tauvina (Forskål) cultured in cages. Rayong Brackishwater Fisheries Station, Brackishwater Fisheries Division, Department of Fisheries. 17 pp (in Thai).

Sakaras, W., S. Sangpradap, and Y. Soodmee. 1990. Experiment on increasing production of brown spotted grouper, Epinephelus tauvina (Forskål), by using artificial hides to increase stocking density. Rayong Brackishwater Fisheries Station, Brackishwater Fisheries Division, Department of Fisheries. 24 pp (in Thai with English Abstract)

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Appendix 1. Flowchart of grouper production and trading from natural seeds and from hatchery-produced seeds

Natural seeds

Natural Seeds (by shelter trap, gill or push netting) -------->Nursing (pond or cage)------>(0.04-0.1$US/1.5cm, 0.08-0.24$US/2-3 cm through middleman, 1/2-1/3 less from fisherman)

Culture (pond or cage)-----> Marketable size------> sold to consumer or middleman for exporting -------> keep for selling to be broodstock

Remark: The pricelist is in Appendix 2 for marketable sizes.

Hatchery-produced seeds

Eggs -------------------> Seeds from Hatchery ------------> Nursing (pond or cage) -------> (350-400/million of egg)