Grouper culture area

In Thailand, more than 40 species of groupers were reported all of them prefer to live in salinity ranged from 12-30 ppt and temperature ranged from 22-28oC. They are sluggish fish always found rest quietly among the rocky or lurching among the coral reef in natural habitat. Grouper are cultured both in cages and in earthen pond but about 90% of farmers culture them in nylon net cages that set in natural seawater.  The cage culture of grouper is being done along the coastal areas at the southern and eastern part of Thailand, i.e. Chumporn, Satun, Krabi, Phuket, Ranong, Trang, Phang-nga, Rayong, Nakhonsrithamarat, Narathiwat, Songkhla, Pattani, and Trard provinces. The area over 3 million square meters that are 15,895 cages are used for fish culture in cage including grouper and seabass and 35.6 % are grouper cages. The pond culturing are found in some provinces as Samutsakorn, Samutsongkram, Petchaburi, Nakhonsri- thamarat, Songkhla, Satun, Chantaburi and Trard provinces. In Suratthani, Pachaburi, Chachongsao and Samutsakorn provinces at some brackishwater areas pond culture of E chachuangsao. malabaricus and E. tauvina are also operated.

Percentage of grouper cages in Satun province reported by Satun Coastal Aquaculture Development Center during 1997-98 (67.85 %) was decreased from 1996 survey by Sangabu, 1966 (88.02%, Appendix Table 2.) by 20.35%. The live fish (1.0-1.2 kg) are exported to Malaysia, Singapore, Taiwan and Hong Kong at market price ranged 2.0-69.2 $US/fish depend on species and season (1$US=40Baht).

Total number of fish cages in Songkhla lake are 4,050 cages and adjacent area 350 cages 90% are Asian seabass, Lates calcarifer. The other 9% are red tilapia or ‘Pla –tup-tim’ only 1% is grouper (Thompolkrang and Predarumpaburt, 1990).

Grouper fry and fingerling sources

         Sources of of grouper fingerlings usually from the same sites of culture areas.  One of the constraints to grouper aquaculture is not enough seed supply from the hatchery, which persisted until now. Generally, there are 1-2 cm fry and 1-2 inches fingerlings are preferred for nursing to 3-5 inches for stocking and culturing on cages.

The 1-2cm fry: Almost of grouper fry in this size are obtained from the wild by trapping. This trap compose of dried twigs or stem of glass called  ‘yan li pow’ put together with nylon net. These were acted as shelter (sometime called ‘pu-m’), they are put in the canal along the mangrove areas and other brackishwater coastal areas and checked every 2-3 hours or longer. These traps will be lift up and fish will be collected by scope net and transported to the middleman or broker for selling to the fish farmers.

Some fishermen use small mesh size (0.5-1.0-cm) gill net block the waterway that grouper fry will pass and collect the fish by lifting the net and scooped up. Some fishermen used the push net for captured the grouper fry. These fry may die easily when stock to the pond due to careless during harvesting and transportation.

The 1-2 inches fingerling: Most of this size are obtained by nursing the 1-2cm by the farmers and middlemen. If from the wild, they are trapped by ‘pu-m’ too.

The 3-5 inches juvenile: These juveniles were collected from small fish trap locally called ‘Sai’ or ‘Lob’. The traps are put every evening in the canal in mangrove areas or hide in the reef area at the island in open sea and marked by the floating flag. The traps are checked the following morning or few days after putting depend on their sense about water current and lunar cycle. Gill net and big trap are also use for catching grouper juveniles in some area.

Nursing of fingerling to juvenile

Grouper, Epinephelus malabaricus and E. coioides fingerling (1.0-2.5 cm) either from the wild or from fish hatchery has to be nursed before culture to marketable size. The concrete tank, nylon net cage and earthen pond are use for nursing facilities.

Concrete tank : Fingerlings are nursed in round or rectangular-shaped concrete ponds or tanks capacity of 1-30 ton with stocking densities of 15-50 inds/m² and fed with minced fresh fish, wet or moist and dry pellets (Panbanpeaw and Sakaras, 1990) at satiation once or twice per day. Grading of size is needed for the homogenous growth and minimized the loss due to cannibalism.

Net cage: Net cage (1x1x1.5 m³) nursing has better results than using concrete pond. Fish have better growth and survival rates in higher stocking density. Stock fingerling size 5.7cm (3.1gm) 300-500 inds/m² fed with trash fish for 75 days can obtain 14.1 cm.(49.9gm) juvenile grouper with survival rate of 91.1%.  Mortality can cause from environmental and water pollution in the area.

Earthen pond: Earthen pond areas of 800m² up to 3,200m are used, they were stocked at 25-100 inds/m² and fed with trash fish. Partially or totally harvesting by seine and sell or transferred to culture. In the earthen pond survival rate of harvested fingerling compared concrete tanks and net cages rather low.

Price of grouper, Epinephelus malabaricus and E. coioides juveniles size 2-3 , 4-5 and 6-7 inches were 0.225, 0.425 and 0.80 $US. respectively  were in January 1998 are also same in February 1999 (1$US = 40 baht).

Culture systems for growout

Culture systems for growout of groupers can mainly separate into 2 systems, the pond culture with static water and cage culture with running water.

The pond culture: The fish pond culture system with static water was practiced. In brackishwater areas, some shrimp farmers converted their shrimp ponds to culture fish and some had modified their pond by digging pond deeper to about 2 meters depth. The detail of fishpond construction and management were reviewed in Ruangpanit and Yashiro, 1994. DOF (1993) recommended good fishpond should have area about 800-1600 m2 and deep about 1.5-2.0 m. The pond may flood out 2-3 times before cleaning by draining water when low tide and pump out all water. Cleaning the pond bottom and use lime for disinfecting and killing some pest (0.06-0.12kg/m2). Fill the pond at high tide and fertilized with chemical or organic fertilizers for good natural feed (plankton) bloom before release juvenile to the pond. In case of big fish (200-300gm) fertilizing the pond may skip. During culture, 40%-70% of water exchange should be done everyday when observed good water quality from the natural source.

At lease 30% of total culture, area should be reservoir for stocking of water before pumping to the culture pond. This can prevent hazardous of environment, parasite and diseases.

Groupers are usually culture in cages at high density, only few farmers do grouper culture in earthen pond. Three farms at Samutsakorn and one in Petchaburi were reported, all were shrimp farms before and face the serious problem on shrimp culturing. Grouper pond culture in Ban Leam district, Petchaburi province was one of those. They converted shrimp pond for culturing grouper by digging 50cm deeper, different sizes of pond are used, 3,200 m2, 6,400 m2, 8000 m2 and 12,800 m2 were used. They nursed fingerlings of 2.5cm (from NICA hatcheries in 1993) in fine mesh net fixed in pond for 1 month. Then released into the same pond (6,400 m2 ) by removing net out. Partial harvesting was done after 14 months culturing. The 1.2-1.3 gm were selected to send for exporting, FCR of  3.6:1 and survival rate of 40 % were estimated. The other pond 8000 m2 stocked with juveniles (300-500gm) bought locally from the trap and transported from Suratani and Ranong with density of 1.5 inds/m2 for 10 months, survival rate was 75.0 % and FCR= 3.2:1(data in June 1994, from Ruangpanit and Yashiro, 1994).

The cages culture: The cage culture is very popular because of its convenience, higher production yield and lower investment cost compared to the pond construction cost. The cage culture system can eliminate the problems of water management during culture period. Grouper and seabass fishcages are located in the coastal provinces in southern Thailand, i.e.Trung, Phangnga, Krabi, Satun, Nakornsri-tummarat, Songkhla, Puket and Ranong etc. and some at the east coast of Thai Gulf, i.e. Chachongsao, Rayong Chantaburi and Trard. Shapes of fishcages always square or rectangular there are several sizes as 1.5x1.5x2.5m3, 2x2x2.5m3, 3x3x2.5m3, 4x4x2.5m3, 5x5x2.5m3 and 10x10x3m3 etc. The mesh size depended on size of fish to be cultured ranged from 1-2.5cm for nursery and 5-7cm for growout.

There are 2 types of fishcage, the fixed and float cages which will be selected depend on location to be operated and funding of the investor. The fixed cage suitable for water not deeper than 2.5 m. and the difference between highest and lowest tidal levels about 50-60 cm. This type is being used in the eastern provinces as Rayong, Chantaburi, Trard and some provinces in southern as Chumporn, Surattani, Songkhla and Pattani etc. The floating fishcage is suitable for culturing in the area which water depth more than 2 m and the difference between highest and lowest tidal levels more than 1 m . Raff or floater makes from wood, bamboo with styloform and steel bar as the fixer to reinforce are used. Suitable for location facing to the open sea i.e. Satun, Trung, Krabi, Ranong and Phangnga etc.

Stocking densities and production : The stocking densities of seabass and grouper in cages are reviews. Seabass net cage culture can stock fish high as 300 fish/m2 (Sakares, 1990) which same as in Songkhla (Ko yo). However, high stocking density with uneven size of initial stocking fry may cause about 50% mortality (Chua and Teng, 1982). The minimum size of juveniles for culturing in growout cage should be in ranged of 7.5-10cm or 3-4 inches. Sakares and Sukbunteang (1985) showed that no different in growth and survival rate of seabass stocked at 24, 36 and 48 fish/m2.  Experiment during 1980-1983 showed density of 100 fish/m2 in 6 months period would have yield of 50 kg/m2 . Further experiment showed good result of culturing seabass in cages at very high density as 150, 200, 250 and 300 fish/m3 at Rayong Brackishwater Fisheries Station resulted in production of 83.2, 109.5, 125.3 and 148.7 kg/ m2 /yr, respectively (Sakares, 1990).

Grouper cage culture was recommended to stock 15 fish/m² since 1980 but fish are stocked at various densities from 30-200 fish/m² (Table 1). The optimum stocked density of grouper for cage culture in brackishwater was demonstrated based on dissolved oxygen budget by Nabhitaphata et al. (1988).  The lower optimum density was 58 fish/m³ or 75 fish/m² with possible stocking limit of 351 fish/m³ or 457 fish/m² for fish up to 500gm, and 31 inds/m³ or 40 fish/m² for fish up to 1.2 kg with possible limit of 187 fish/m³ or 244 fish/m².  Sakares et al.(1990) showed no statistical difference on growth, survival rate and fatness of the fish cultured in the optimum stocking density (75 fish/m²) and high stocking densities 100 and 125 fish/m² with addition of artificial shelters, but the production/cage were higher and FCR were lower in the high stocking densities. This result can use as basis for increasing more production in grouper cage culture depend on culture site, soil substratum and water quality.  Example of various stocking densities and production of grouper cage culture are showed in Table 2.

Management of net cages is necessary, the net is sometime blocked by sediment and sometime have mollusk and seaweed attached. These may cause diseases or parasite attack the cultured fish because of  water circulation and increase weight of the cage. Therefore, its necessary to change to the other set of cage, clean and dry the netting materials every 1-2 month depend on rate of accumulation of those unwanted dirties.  Raff, sinker and float also have to be checked regularly. For high stocking density, sometime partial harvesting is recommended to eliminate the loss due to cannibalistic habit of seabass and grouper.  Stocking fish at various time and rotation of the harvest is recommended for having continuous income. Water and sediment parameters from the grouper cage culture for 3-4 years in Satun province showed high accumulation of organic metter in term of nitrogen and phosphorus in the cage culture area if over three years of culture (Songsangjinda et al., 1993).

Majority of fish farmers use trash fish as feed for seabass and grouper these fish composed of different kind of small fishes i.e. the Yellowstripe trivially (Selaroides leptolepis), Thread fin bream (Nemipterus hexodon), Fringescale sardinella (Sardinella fimbriata), and Round scad (Decapterus russelli) etc. minced, chopped, cut or whole body depend on size of fish to be fed. These trash fish give nutritional unbalance i.e. high in protein level but lack of some vitamins especially vitamin C. In nursery period which use only meat no bone some minerals are also lacking. If sardine is used, it always have enough essential fatty acid but for other fish, in the season which fish have no fat it will also have not enough essential fatty acid. The seabass will show red body symptom. In case not fresh trash fish is used, some protein were degraded and converted to histamine, ammonia and hydrogen sulfide, some property of fat is changed and loss or less effective of many vitamins and minerals as vitamin C, A, B, D, E, Choline and Niacin etc. It may introduce diseases infection to the fish.

Table 1. Grouper cage culture at various stocking densities (6 months) which showed no difference on growth and survival rate but production yield were higher as stocking density was increasing

Problems, constrains and research needed

1.      Diseases are the serious problems for grouper culturing. The bacterial and viral diseases sometime gave high mortality to the pond and cage culturing. Research on prophylactic, chemically and self-immunization enhancements in order to prevent the occurrence of diseases are very importance.

2.      Nutrition of the local available feed as trash fish, and developments of acceptable formulated feed for grouper are have to research. This can save time in the culturing period by improve the growth of cultured fish.

3.      Environmental harzadal and pollution in the culture area always the cause of mass mortality. Research for environmental management and improvement of culture system are recommended.

4.      Pouching is one of the social problem concerns with the human relationship and discipline of people in the culturing site. It also concerns indirectly with the economic situation in the area.

5.      Genetics improvement and breeding program of grouper fishes are recommended to be the importance researches to be carried soon as possible. This may illuminate problems of inbreeding which fish may carry recessive gene, which might prone to get diseases and decrease growth rate etc. 

Literature Cited

Chua T. E. and Teng, S. K. 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. Aquaculture, 27: 273-283.

Department of Fisheries. 1993. Manual for Brackishwater Fish Culture, Department of Fisheries, Ministry of Agriculture and Cooperative. 38 pp. (in Thai).

Doi, M., M., bin Hj. Mohd Nawi, N. R. bin Nik Lah and Z. bin Talib 1991.  Artificial propagation of the grouper, Epinephelus suillus at the marine finfish hatchery in Tanjong Demong Terengganu, Malaysia. Department of Fisheries, Ministry of Agriculture, Malaysia. PP. 41.

Hunsopa, Y., Jindamaikul, T., Sukaputh, S., Riewthong, W. and Duangsa, T. 1990. Study on breeding and larval rearing of red spot grouper Epinephelus tauvina Phuket coastal development culture center. Technical paper No. 36, 24 pp.

Julavitayanukul, P., Putinowarat, C. and Suteemechaikul, N. 1987.  Study on breeding of grouper, Epinephelus tauvina. Review of the  research on grouper culture conference 23-25 February 1987 at NICA pp. 74-81.

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

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

Panbanpaew, S., and Sakaras, W., 1990. Experiment on sea grouper, Epinephelus malabaricus, with dry pellet. Technical Paper No. 38/1990. Rayong Brackish water Fisheries Station Brackishwater Fisheries Division Department of Fisheries. 17 pp.

Ruangpanit, N. and Yashiro, R. H. 1994. A review of grouper, Epinephelus spp. and seabass, Lates calcarifer culture in Thailand. Paper presented in the workshop in Hawaii.

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

Ruangpanit, N., Bunliptanon, P. and Kongkumnerd, J. 1993a. Progress in the propagation and larval rearing of the grouper, Epinephelus malabaricus. p.32-42 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.

Sakares, W. 1990. Experiment on Sea bass, Lates cutcarifer (Bloch), Cultured in Cages with Dry Pellet. Technical Paper  No 5/1990. Rayong Brackishwater Fisheries Station, Coastal Aquaculture Division, Deparsment of Fisheries. 15 pp.(in Thai with English Abstract).

Sakares,W, and Sukbuntaung, S. 1985. Experiment on grouper, Epinephelus tauvina (Forskal) in Cage with Different Stocking Dentity. Technical Paper No. 1/1985. Rayong Brackishwater Fisheries Station, Brackishwater Fisheries Division, Department of Fisheries. 28 pp. (in Thai with English Abstract).

Sakaras,W.and Kumpang, P.1987a. Effect of Stocking Density on Growth and Production of estuary grouper, Epinephelus tauvina (Forskal), Cultured in Cages. Technical Paper No. 3/1987. Rayong Brackishwater Fisheries Station Brackishwater Fisheries Division, Department of Fisheries. 24 pp. (in Thai with English Abstract).

Sakares, W. and Kumpang, P. 1988. Growth and Production of Brown Spotted Grouper, Epinephelus tauvina (Forskal) Cultured in Cages. Rayong Brackishwater Fisheries Station Brackishwater Fisheries Division Department of Fisheries.17 pp. (in Thai).

Sakares, W., Sangpradab, S. and Soodmee, Y. 1990. Experiment on Increasing Production of Brown Spotted Grouper, Epinephelus tauvina (Forskal), by using Artificial Hides to Increase Stocking Density. Rayong Coastal Aquaculture Station Coastal Aquaculture Division Department of Fisheries. 24 pp. (in Thai with English Abstract).

Sanbuga, T. 1996. Area of Coastal Aquaculture in Southern Thailand during September 1994-september 1995. Extension paper 1/1996, National Institute of Coastal Aquaculture, 34 pp. (In Thai).

Songsangjinda, P.; Na-anan, P. and Tanvilai, D. 1993. Water and sediment quality in grouper cage culture area at Klong Pakbara, La ngu District, Satul Province. p. 112-119.  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.

Thompolkrang, P. and Predalumpaburt, Y. 1999.  Coastal aquaculture areas and water qualities survey in Songkhla Lake and coastal zone by using satellite  image and geographic information system. Techical paper No 1/1999.  National Institute of Coastel Aquaculture, 53 pp.

Yashiro, R. 1996.  Status of grouper breeding and culture in Thailand. Paper presented at the Workshop on Aquaculture of Coral Fishes and Sustainable Reef Fisheries. Sabandar Bay Resort, Tuaran, Sabah, Malaysia 4-8 December 1996. 17 pp. 

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Appendixes

Table 1.     Location and numbers of grouper cage culture in Thailand (from Yashiro, 1996)