The effect of artificial nests on reproductive performance in the Nile tilapia, Orechromis niloticus L., spawned in net hapas | |
| Author | Bevis, Randall |
| Call Number | AIT Thesis no. AE-94-29 |
| Subject(s) | Tilapia Fishes--Spawning |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources & Development |
| Publisher | Asian Institute of Technology |
| Abstract | Artificial nest sites were placed in 20 m2 nylon hapas for a series of four short tilapia spawning experiments, which were conducted from February through May 1994 in Udon Thani Province, northeastern Thailand. The first two experiments were used to determine what size (0 . 25 m 2 or 0.5 m2) and depth (15 or 30 cm) of nests would give the best spawning r esults for both large and small broodfish. In Experiment 1 large males of 318 g and females of 180 g were stocked at 100 fish per unit at a 1:1 sex ratio. In the second experiment small males of 69 g and females of 51 g were stocked at 120 fish per unit also 1:1 sex ratio. The small shallow nests (0 . 25 m2 x 15 cm) gave the best performance over a range of spawning indicators and were selected as the nests to be used for the third and fourth experiments which both used the small broodstoc k. The third experiment used densities of 50, 100 or 200 fish (1 :1) and 0, 40 or 80 nests per unit. Total seed production did not significantly improve with the addition of nest treatments over the 4 seed harvests (p>0.05). But when analysis was done for fish wi th prior experience to nests (harvest 1 excluded) artificial nest did produce sign ificantly more seed (p<0.05). Early viability and clutch sizes (stage 1 eggs) were found to increase significantly from 0 to 80 nests per unit for broodfish densit i es of 100 and 200 fish (p<0.05). The fourth experiment used 200 fish per unit in sex ratios of 1:1, 2:1 or 3:1 with 0 or 80 nests. Total seed production was not significantly different among sex ratios or nest treatments. Egg viability was significantly higher for eggs from 80 nest treatments in 1:1 and 2:1 sex ratios (p<0.05). High temperature and low dissolved oxygen levels were also seen to negatively effect spawning intensity and early viability during this experiment. |
| Year | 1994 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Little, David C. |
| Examination Committee(s) | Yakupitiyage, Amararatne ;Lin, Chang Kwei |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1994 |