Realizing the need to develop a practical method of tilapia seed production, AARM has developed a hatchery technology through intensive research efforts over the last decade. It includes management of broodstock in jumbo hapas (120 m^2) suspended in fertilized ponds, harvesting of seed at early stages from the mouths of incubating females, staging of collected seeds, artificial incubation in special jars supplied with clear filtered water, larval rearing in shallow trays supplied with coarse gravel filters and feeding of 17-alpha methyltesterone mixed with high quality fish meal in small hapas (5.4 m^2). Several techniques are in use in various parts of the world to produce all-male tilapia fry but the above system has unique features.
Various attempts were made to disseminate and commercialize the hapa-based AIT hatchery technology without success. Finally, a hatchery farm named 'Nam Sai Farm' located at Ban Sang district of Prachiburi Province, Thailand, was established through a joint venture agreement with Narai Technologies Co., Ltd. The farm sold 41.8 million sex-reversed tilapia (Oreochromis niloticus) fry since its establishment in 1994 to 1996. Then in 1997, sales reached 53.4 million fry, giving a total production of 95.2 million. The sale surpasses 100 million if the first quarter of 1998 is added.
Based on the joint venture agreement, AIT initially supplied broodstock fry and especially designed incubators to the joint venture hatchery. In addition, AIT provides technical assistance, conducts on-farm research trials, monitors the quality of fry each month and provides certification to the farm. The farm has to produce fry with more than 99% male (AIT's standard) in order to receive this certificate. As the price of sex-reversed fry in Thailand is 4-5 times higher than the normal fry, the business can survive only if it can produce fry of superior quality. Quality, in terms of percentage of males, is monitored regularly.
A total of 6810 fry were examined under microscope in 36 tests over a period of 2 3/4 years with an average of 189 +/- 13 (SE) fry per test. In general, 5-10 cm in total length or 3-10 g in weight were experienced to be suitable size, which can be achieved after nursing for about 1 1/2 to 2 months depending on the food availability. The lowest percentage of male obtained was 85.7%. The quality was variable in the first year of hatchery establishment, however, it was well maintained from the second year onwards. Unpredictable quality in the first year was suspected to be due primarily to improper mixing of hormone which was improved by bringing a few workers to AIT for each careful observation of the mixing procedure. Another possible cause might have been the excessive natural food abundance in the fry rearing ponds (excessively green) which was evident from the higher growth of sampled fry as compared to the fry from the same batches reared in the ponds at AIT; and the contamination of sample while rearing in the pond caused by bird or jumping of fry from the pond into the hapa. However, chances of contamination were very limited.
In addition to the gonad squash method, a telephone survey was conducted in order to assess the quality of fry through customer's satisfaction. A total of 10 fry customers (out of about 80 customers) were randomly surveyed. 60% of the respondents knew the product from their neighbors, 20% from magazine, and the remaining 20% from other advertisement. All the contacted customers expressed that the fry produced by AIT's joint venture hatchery were very good in quality. The reason for the satisfaction were: no reproduction (30%), very few fry (recruits) appeared in the pond (20%), uniform in size (30%); and high survival rate (20%). A survey report also revealed that the growth performance of the fry produced by the farm was higher as compared to the fry produced by other farms. The farm has, therefore, established its name among the fish farmers in Thailand as the best producer of sex-reversed tilapia fry after AIT.
As AIT produces and sells only 1-2 million fry per month which is far bellow the demand, the joint venture farm has been the major supplier of sex-reversed tilapia fry in Thailand. The technology developed at AIT through intensive research over hte past decade has proven to be simple, economically viable and a practical method for tilapia fry production on a commercial scale. Realizing tilapia as a potential fish species to supply animal protein for the poor, AIT is disseminating the hatchery technology through, not only through its Outreach and hands-on training programs, but also through the private sector's participation. The joint venture hatchery (Nam Sai Farm) has an ambitious plan for expansion. In addition, AIT's joint venture partner (Narai Technologies Co., Ltd) plans to establish new hatcheries in Thailand and other countries in the region although the company faces the problem of lack of qualified, enthusiastic and energetic managers and technical assistance. Nevertheless, the private sector participation will help solve the problem of short supply of quality tilapia seed in the region quickly and effectively.
For more information, contact:
Ram Bhujel
AASP/SERD/AIT
PO Box 4, Klong Luang
Puthumthani 12120, Thailand
Tel: 662-5245486, Fax: 662-5246200
e-mail: aasp@ait.ac.th
(article by Ram Bhujel in Newsletter of the Agricultural and Aquatic Systems Program (AASP), Vol. 3, No. 2, April 1998)