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Broodstock development of giant grouper, lanceolatus.

Vichai Vatanakul, Janjit Kongkumnerd, Sunit Rojanapitayakul, Renu Yashiro and Poonsin Panichasuke NICA*, Songkhla

(Translated by Mr Hassanai Kongkeo) Abstract Broodstock development of giant grouper was conducted in net cages (5.0x5.0x3.0 m3) at Nu Island, Songkhla. Giant (258.30±111.00 gm and 4,410.00±90.00 gm) were stocked at the density of 3 and 1.5 /m2 respectively. Fish were cultured for 4 years and fed with trashfish. The result showed that growth rate of the 1st, 2nd, 3rd and 4th years were 500.99–646.00; 456.67–674.50; 650.00–694.16; and 507.50– 588.57 gm/month respectively. The 3rd year of the experiment, sperm milt could be observed when stripped at the abdominal part of male. In the 4th year, eggs and sperm could be observed. The first successful positive spawning response of the giant grouper by HCG and Puberogen injection. The result indicated that giant grouper can be cultured in net cages for broodstock development. Water quality parameters during cultivation period were pH: 7.17-8.43, salinity: 0-34 ppt, alkalinity: 52-220 ppm while nitrate, nitrite, ammonia-N and total P were 0-0.277, 0-0.048, 0-0.0237 and 0.001- 0.468 ppm respectively.

NICA*=National Institute of Coastal Aquaculture, Songkhla 90000, Thailand Introduction Giant grouper Epinephelus lanceolatus is the largest grouper which can be found in both Andaman Sea and Gulf of Thailand, particularly in Phuket, Trang, Krabi, Satul, Chantaburi, Trad and Cholburi Provinces (Boonliptanont P., 1997). Small size fish is better taste and very expensive as it is the most favourable fish among Chinese. It can be found in estuaries, mangrove areas and river mouths. There is world wide geographic distribution of this fish such as East Africa, Red Sea, Pakistan, south China, south Japan, Hawaii, Australia and Fitkalin Island (Heemstra and Randall, 1993). There has been giant grouper culture in Thailand but it was not expanded due to limited amount of wild fries. Most of giant grouper production are by product from cage culture of other grouper as it is difficult to identify the species of wild grouper fingerlings. In order to promote new economic fish for marine aquaculture, giant grouper has been selected as a promising species due to its fast growth rate. The cultured giant grouper can reach 1.0 kg within 4 month (Boonliptanont P., 1997). Many shrimp farmers would like to have alternate species due to the decrease in Broodstock development of giant grouper Page 2 of 6

shrimp production mainly caused by environment and pond deterioration. Giant grouper is one of the required species by these farmers as it can yield very good price and high demand in international markets. Therefore the Coastal Aquaculture Division, Department of Fisheries initiated the broodstock development programme for further fingerling production in order to promote giant grouper culture in the future. Materials and methods Giant groupers were collected from commercial net cages in Trang Province (285.30±111.58 gm body weight and 26.12±3.31 cm length in average) and Phang-nga Province (4,410±90.00 gm body weight and 60.35±4.38 cm length).They were separately cultured in net cages (5.0x5.0x3.0 m3) with stocking densities of 3 and 1.5 fish/m2 respectively.

Net cages: 5.0x5.0x3.5 m3 cages were built in 20.0x20.0 m2 raft supported by polyfoam blocks. Sizes of polyethylene nets for small and large fish were 1.5 and 3.5 inches respectively.

Feeding: Once a day, fish were gradually fed until fish stopped feeding by fresh sardines which were chopped according to the sizes of fish mouths.

Data collection:

1. Growth rates were recorded by measuring total length and body weight monthly from sampled 10-20 fish. 2. Gonad developments were studied from sampled fish by measuring body weight, body length and gonad weight. Gonad tissues were preserved in Bouins fixative for further study on gonad development using Yamamoto, 1956 method. 3. Mature eggs were checked by inserting a plastic tube of 2 mm diameter into oviduct and sampling some eggs (generally over 0.42 mm size). Male broodstock were considered matured if they released white milt after gently pressed on their abdomens. Spawning was induced by hormone injection. Broodstock were initially injected by HCG at the rates of 150 and 500 IU/Kg B.W. and followed by Puberogen hormone at the rates of 100, 200 and 300 IU/Kg B.W. respectively.

Data analysis: Data were analysed by SPSS programme which was translated into Thai by Ngamsantiwong T., 1995. Results 1. Growth rates, food conversion ratios and survival rates of giant grouper broodstock cultured in net cages at NICA substation, Nu Island were observed. In Figure 1, the

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average growth rates in 1st, 2nd, 3rd and 4th years were 500.99-646.00; 456.67-674.50; 650.00-694.16 and 507.50-588.57 gm/month respectively. The final weight and length at the end of experiment were averaged as 28.27-28.31 Kg and 109.16 cm respectively. In Table 1, the increases in body weight and length were 15.91-19.46 gm/day and 0.035-0.058 cm/day respectively. Specific growth rate for body weight was 0.15-0.37% per day and for body length was 0.07-0.11% per day. Average food conversion ratio and survival rate were 3.85-4.09:1 and 24-84.44% respectively.

(A) (B)

Fig. I Weight gain of giant grouper culture in net cage with stocking density 3/m3 (A) and 1.5/m2 (B)

Table I Results of growth rate, Food conversion rate ratio and Survival rate of giant grouper cultured in net cages.

Net Specific growth Weight gain Food Survival cage rate (%/day) Conversion Rate Year No. g./month cm./month Weight Length rate (%) 1st I 500.99 3.11 0.97 0.30 3.94 58.66 II 646.0 2.20 0.30 0.10 3.78 91.11 2nd I 674.50 1.83 0.25 0.08 3.29 55.26 II 456.67 0.84 0.11 0.04 3.97 88.88 3rd I 694.16 1.48 0.13 0.05 4.26 30.00 II 650.0 1.01 0.11 0.03 4.63 86.67 4th I 507.50 0.50 0.13 0.02 3.89 24.00 II 588.57 0.14 0.07 0.11 3.96 84.44 Average I 594.29 1.73 0.37 0.11 3.85 II 585.31 1.05 0.15 0.07 4.09 Broodstock development of giant grouper Page 4 of 6

2. Gonad tissues were observed from sampled broodstock for gonad development. It was found out that ovary development in the third year was in the tertiary growth phase with average body weight of 20.08 Kg and average GSI of 1.04 (0.664-1.47).

3. The results from first injection with HCG 150 and 500 IU/Kg B.W. and followed by injection of Puberogen at the rates of 100, 200 and 300 IU/Kg B.W. respectively were 11 females spawned and 164,550 larvae developed (Table 2).

Table II Number of eggs spawned, Ferlilization rate and hatching rate

Number Eggs spawned Hormone % % Date 3 Larvae (x 10 ) Fertilization Hatching 10/10/1998 HCG 1,021 62.0 9.99 102,150

11/10/1998 Puberogen 400 22.6 0.0 0

11/10/1998 Puberogen 1,001 9.9 0.0 0

11/10/1998 HCG 1,021 61.8 6.1 62,400

12/10/1998 Puberogen 802 12.9 0.0 0

13/10/1998 Puberogen 621 8.9 0.0 0

14/10/1998 HCG 120 0 0.0 0

9/11/1998 HCG 1,620 0 0.0 0

21/11/1998 HCG 1,744 0 0.0 0

21/10/1998 HCG 640 0 0.0 0

21/10/1998 HCG 121 0 0.0 0 Average Total 828.3 16.1 1.45 164,550

4. Water quality parameters during experiment were as follows:

pH = 7.17-8.43 salinity = 0-34 ppt alkalinity = 52-220 ppm nitrite-N = 0-0.048 ppm Broodstock development of giant grouper Page 5 of 6

nitrate-N = 0-0.277 ppm ammonia-N = 0-0.237 ppm phosphorus = 0.001-0.468 ppm Conclusion and discussion It is possible to culture giant grouper broodstock in netcages until they . At the end of 4-year experiment, average body weight was 28.27-28.31 Kg with weight increase at the rate of 19.51-22.76 gm/day and length increase at the rate of 0.035- 0.058 cm/day. The average specific growth rates for body length and weight were 0.046-0.0993% per day and 0.144-0.32% per day respectively. It can be concluded that giant grouper is the fastest growing species in comparision with the body weight increase at the rate of 2.3-2.9 gm/day in other grouper (Sakares W. and P. Kampang, 1987). Feeding by fresh sardines, food conversion ratios in giant grouper ranged from 3.29:1 to 4.26:1 which were close to the study of Boonliptanont P., 1997 (3.72:1). However, its FCR is still lower than estuarine grouper (6.78:1) which was studied by Sakares W. and P. Kampang, 1987. Survival rate in one experiment was unfortunately poor due to grouper diseases spread from nearby grouper cages. In another experiment, survival rate was high because fish were stocked after disease spread. For gonad development in giant grouper, males became mature at the average weight of 17.585±2.681 Kg and at the average length of 97.971±11.0981 cm. Mature eggs were observed when the average body weight and length of females were 25.03±6.4 Kg and 102.64±12.86 cm respectively. It was found out by Boonliptanont P, 1997 that gonad development in giant grouper started when fish reached 2.5 Kg weight and the smallest female with mature eggs was 15.21 Kg in size. In his experiment, the average body weight of females with mature eggs which could be detected during breeding season, was 22.08 Kg.

It was found out that the smallest size of eggs suitable for induced breeding by hormone injection (HCG:150 and 500 IU/Kg B.W. and followed by Puberogen: 100, 200 and 300 IU/Kg B.W. with 24 hours interval) was 0.42 mm. As 164,550 larvae have been produced in the first success in artificial breeding of giant grouper, it can be shown that its broodstock can be artificially developed by netcage culture. References Ngamsantiwong Tawatchai, 1995. SPSS/PC+SPSS for Windows: Principles and methods for the use of computer in statistics for research, Information Division, Office for Technology Development, King Mongkut Institute of Technology, North Bangkok Campus, 301-357.

Boonliptanont Paiboon, 1997. Some biological study of Epinephelus lanceolatus (Bloch), Scientific Paper No. 2/1997, Coastal Aquaculture Division, DOF, 19 Broodstock development of giant grouper Page 6 of 6

pp.

Sakares Wichien and Pornchai Kampang, 1987. Effect of stocking densities on the growth and production of grouper in netcages, Scientific Paper No. 3/1987, Rayong Coastal Aquaculture Station, Coastal Aquaculture Division, DOF, 24 pp.

Heemstra, P.C. and J.E Randall, 1993. FAO Species catalogue Vol.16: Grouper of the world, FAO Fisheries Synopsis No. 125, Vol 16, FAO Rome, 172-175

Yamamoto, K. 1956. Studies on the formation of fish eggs: 1. cycle in the development of ovarian eggs in the flounder, Liopsetta obscura, J. Fac. Sci., Zool., Hokkaido Univ, 12:362-373.