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Title: Studies on the reproductive biology of Oreochromis niloticus L
Author: Srisakultiew, Penpun
ISNI:       0000 0001 3476 0487
Awarding Body: University of Stirling
Current Institution: University of Stirling
Date of Award: 1993
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This study investigated the reproductive biology of Oreochromis niloticus broodstock of known age structure and spawning history with the aim of synchronising and controlling their spawning for mass fry production. Hatchery reared stock was subjected to a constant photoperiod of 12L:12D and maintained at 27 ± 1°C. All stock was fed on commercial trout pellets. The feeding frequency and protein content of the diet varied depending on fish size. Oocyte development was classified into 6 stages including that of atresia based on histology. In order to quantify ovarian maturity, three stereological methods were compared. The ovarian volume fractions of different oocyte stages estimated by the mass, graphical and intersection methods showed homogeneous results. The intersection method required less time (2.6 mins/sample) whereas the others needed 11-12 mins/sample. In addition, the numerical density technique employing the intersection method was used and yielded similar oocyte estimates to those derived from the Gilson's fluid method. Onset of sexual differentiation was influenced by the stocking densities. At 10 and 20 fry/l, 30 and 45% of those fry, respectively, were sexually differentiated by day 11 post-hatch, whereas those held at 2 fry/l were not. Gonadal development was monitored in fish of known age. Fry were randomly sampled after hatching at two week intervals until 24 weeks. Total body length and weight were recorded and gonads were fixed for maturity determination. Serum samples were analyzed for total calcium (Ca2+), testosterone (T) and oestradiol-17ß (E2). The males grew faster than the females of the same age and showed secondary sexual characteristics and attained maturity with significantly (P<0.05) higher T levels by 16 and 22 weeks, respectively. Females in comparison showed a significant (P<0.05) increase in GSI during 18-24 weeks (0.5-3.6%). The volume fraction of stage 6 oocytes, which were positively correlated to GSIs (r2=0.84; P
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Nile tilapia ; Fishes Reproduction