1997
D. Tech. Sc. Thesis by Suchart Ingthamjitr
Abstract:
Hybrid Clarias catfish (Clarias macrocephalus x Claria gariepinus) is a cultured fish of major economic importance in Thailand. Recently, the hybrid catfish have faced with slow growth and poor survival. This study focuses on catfish hatcheries in central Thailand and based analysis on technical, economic and social information 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.
Small-scale hatcheries produce catfish fry as a part-time activity, relying on purchased female broodfish whereas larger hatcheries were full-time and often produce their own broodstock. Although many hatcheries produce fry during the cool season (October to January), only three hatcheries produce 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 better quality fry as a result. Technologies used to incubate fertilized eggs and larvae were similar irrespective of the hormone used.
(from AASP Newsletter, Vol. 3, No. 2, April 1998)