The reproductive biology of snakeskin gourami (Trichogaster pectoralis Regan) and intensification of seed production | |
| Author | Ruangvit Yoonpundh |
| Call Number | AIT Diss. no.AS-97-05 |
| Subject(s) | Trichogaster Fish-culture |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | This study sought to determine methods to intensify snkeskin gourami (Trichogaster pectoralis Regan) seed production in Thailand. A shortage of seed for stocking currently limits the development of more intensive culture systems, and the spread of Trichogaster farming from its main culture areas, which are now within a major industrial zone. The intensification of seed production in this study was based on the use of environmental and hormonal manipulation of broodfish conditioned and spawned naturally in hapa-in-pond systems. The annual reproductive cycle of males and females was observed under culture conditions over a period of 15 months and correlated with environmental parameters. The effects of substrate type, quantity and broodfish density on seed production were evaluated in a series of experiments. The effect of multiple spawning was analysed with respect to the quality of seed produced and incubated under controlled conditions. Optimal densities for nursing fry based on the stocking of first feeding larvae in fertilized earthen ponds were determined. A survey of current Trichogaster farming practices in the main culture area in Thailand, Samutprakarn province, was carried out to assess the impact of various levels of industrialization. A positive relationship was found between gonadal development and environmental factors, such as rainfall, air and water temperatures clearly indicating a species adapted to spawning in the early monsoon period. Histology of ovaries revealed that snakeskin gourami was a multi-clutch, group-synchronous spawner. Both natural and artificial spawning substrates were effective as environmental cues inducing natural spawning success in pairs of mature gourami, and the density of substrate had no effect on the success of hatchery-based incubation (P>0.05). The optimal stocking density for social, natural spawninf was found to be 2 fish/m in a clear water pond. High levels of turbidity appeared to inhibit spawning. Repeat spawning after hormonal inducement during the season was demonstrated after 45, 60 and 90 days conditioning without any loss in seed quality; relative fecundity was positively related to duration of conditioning. A third spawning, after 45 day conditioning intervals resulted in poorer quality seed. A negative relationship was observed between individual growth and fry stocking density (r = -0.58, P<0.01), whereas a positive logarithmetric relationship occurred between survival and density (r = 0.78, P<0.01). Overall, the highest stocking density (300 fry/m) evaluated proved optimal. The level of locak industry had a significant effect on Trichogaster culture. It was found that more experienced farmers in areas with more industrial development had intensified management practices. Production levels were significantly higher in the operations of more experienced farmers in more industrially-affected areas. Wild fish formed an important component of harvests and were often stocked to ensure adequate recruitment. The results of this study can be used as framework for the intensification of snakeskin gourami seed production. The potential of the snakeskin gourami as a candidate for more intensive, waste-fed polycultures appears promising. |
| 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) | Lin, Chang Kwei ; |
| Examination Committee(s) | Little, David C.;Yakupitiyage, Amararatne;Dale, Reidar;Beveridge, Malcolm C.M.; |
| Scholarship Donor(s) | Royal Thai Government,; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1997 |