Type of Document Master's Thesis Author Glenney, Gavin W. URN etd-08292008-063206 Title Comparisons of tilapia seed production under various broodstock densities and fry stocking densities Degree Master of Science Department Fisheries Science Advisory Committee
Advisor Name Title Hallerman, Eric M. Committee Chair Libey, George S. Committee Chair Murphy, Brian R. Committee Member Smith, Stephen A. Committee Member Keywords
Date of Defense 1996-12-10 Availability restricted Abstract
Four methods of seed (eggs, sac-fry, and fry) production for Rocky Mt. White hybrid® tilapia, (0. niloticus x O. aureus), were compared under green water conditions over a six month period in an environmentally controlled greenhouse at the Virginia Polytechnic Institute and State University's Aquaculture Research Laboratory. Twelve 3 m2 rectangular tanks were stocked with brood stock (mean wt. 680 g), at a sex ratio of 3 females to 1 male. Nine tanks were stocked at one of three densities (1, 2, and 4 females m-2), and seed was collected from females' mouths weekly. Three additional tanks were stocked at a density of 2 females m-2, and fry were collected from the edges of the tanks when seen.
Seed production was among the highest seen for related studies. Average number of viable fry produced at I females m-2, 1660 fry female- I month-I, was significantly higher than the combined average production of densities 2 females m-2 (629 fry female- I month-I) and 4 females m-2 (695 fry female-1 month- 1) (p< 0.02). Even though there was no significant difference between viable fry production meter-2 (p>0.05), the highest density consistently produced more fry meter-2. No significant difference was observed in viable fry production between the two seed collection methods (Clutch removal- 629 fry female-1 month-I; Natural mouth-brooding- 520 fry female-1 month-I) (p>0.05).
The effects of stocking density on growth and survival were evaluated by stocking 14-16 day old artificially incubated fry (25.5 ± .32 mg, 12.1 ± .04 mm), into 150 liter troughs at three densities (3, 6, and 12 fry liter-I) under green water conditions for 30 days. The mean monthly hatchery seed survival was 65.7 ± 2.3%, which varied largely depending on initial seed developmental stage. Significant differences were observed between mean weight, length, survival, and feed conversion ratios among the various fry stocking densities (p
These results that to maximize fry production and reduce labor, a density of 4 females m-2 or higher be used under the natural mouth brooding seed collection method. They also suggest a fry density between 6 to 12 fry liter-1 should be used with periodic grading or sex reversal to reduce cannibalism and increase growth.
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