Hybrid Clarias catfish seed production and marketing in central Thailand and experimental testing of seed quality | |
| Author | Suchart Ingthamjitr |
| Call Number | AIT Diss. no.AS-97-06 |
| Subject(s) | Fish-culture--Thailand, Central Catfishes--Thailand, Central |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Hybrid CIarr'as catfish (CIan'as macrocephabrs x C [arias garieprrms) is a cultured fish of major economic importance in Thailand. Culture of Thai native catfish became established over 30 years ago, but introduction of the hybrid in the late 1980's revolutionized the scale and importance of the industry. Recently, farmers raising the hybrid catfish have been faced with slow growth and poor survival of their stocked fish, in addition to high competition and low profit margins. Initial surveys traced some of these problems to hatchery practices and led to a research framework to analyze the technical and economic status of catfish hatcheries. The study focused on catfish hatcheries in central Thailand and based analysis on technical, economic and social data collected between April 1995 to May 1996 from thirty hatcheries. Fry were assessed for quality during the early and mid-spawning season from different hatcheries using a salinity challenge stress test. A clear dichotomy of scale was observed in hatchery operations in central Thailand based on annual production (defined as small<73 million or large>73 million catfish fry). A major center of catfish hatcheries was found to be Nong Kae district in Sara Buri province and Nong Sua district in Pathum Thani province. The relative advantage of this area was its proximity to both a major source of female broodfish (Clarias macrocephalus) and live feed (Moina macrocopa). Female broodfish used to produce hybrid Clarias fry are mainly from Trichogaster culture farms in Chachoengsao and Samutprakarn province. The other significant factor is the development of mass production of the water flea (Mama macrocopa) pioneered by Pathum Thani Fisheries Development Station. Moina is required by hybrid Cian'as hatcheries in large quantities. Small—scale hatcheries tended to produce catfish fry as a part-time activity, relying on purchased female broodfish whereas larger hatcheries were full-time and often produced their own broodfish. Although many hatcheries produced fry during the cool season (October to January), only 3 hatcheries produced fry year-round. Gonadotropic-releasing hormones were the most popular class of hormone used to stimulate ovulation, partly due to the effectiveness of a single injection. However, some larger hatcheries continued to use whole pituitary glands, claiming that better quality fry as a result. Technologies used to incubate fertilized eggs and larvae were similar irrespective of the hormone used. Application of a Cobb-Douglas production function identified female broodfish biomass used as the dominant explanatory variable for fry production; this input made up between 79— 87 percent of variable costs. Break-even analysis indicated that small-scale hatcheries had lower efficiencies of production than large-scale ones. Marketing of fry by hatcheries was sophisticated, involving their direct marketing to food fish farmers. or via middlemen and nurseries. Fierce competition has stimulated hatcheries to offer free transportation or live feeds to customers buying large numbers of seed. A challenge stress test was developed based on survival of yolk-sac fry at a salinity of 12 ppt. over a 60 minute period. Survival was compared to performance over a period of nursing. Fry quality was found to vary greatly with season; poorest quality fry were produced early in the year. Seed quality tests indicated superior quality fry were produced from female broodfish maintained and conditioned within the hatchery rather than from fish purchased and spawned immediately. The use of stress tests by hatcheries and their customers could enable them to identify poor quality fry at purchase; this could reduce the costs and risks attached to hybrid catfish production considerably. |
| Year | 1997 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Aquatic Systems(AS) |
| Chairperson(s) | Demaine, Harvey;Little, David C.; |
| Examination Committee(s) | Macintosh, Donald J.;Johri, Lalit;Boonjit Titapiwatanakun; |
| Scholarship Donor(s) | Overseas Development Administration (U.K.); |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1997 |