Theses and Dissertations


Title: Evaluation of reproductive and growth performance and microsatellite variability of four strains of Nile tilapia (Oreochromis niloticus, L)

Name: Osure, George Owiti

Degree: MS

Chair: Ronald P. Phelps

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2003

Pages: 95

Keywords: reproductive,growth performance,microsatellite variability,Nile tilapia,Oreochromis niloticus

Abstract:

Tilapia have gained recognition as important aquaculture species in tropical and sub-tropical climates and have become one of the most abundantly produced fish in aquaculture. Nile tilapia, native to various regions in Africa, is one of the primary species being cultured. Much of the stocks being cultured are based on a limited number of collections from the wild which may differ in their reproductive and growth characteristics. An evaluation of reproductive and growth characteristics and microsatellite variability of four strains of O. niloticus was done at Auburn University, studying three domesticated strains (Egypt, Ivory Coast and Sagana) and one wild (Lake Victoria) strain. In the first part of the study, strains were evaluated as to their reproductive characteristics and growth potential at different life stages and under different management conditions. Brood fish were stocked into individual 2 m3 hapas suspended in 20 m2 concrete tanks at the ratio of 3 males to 7 females. Four replicate hapas were used per strain. Hapas were checked every 7 days for females holding eggs or sac fry in the mouth. Females holding eggs or sac fry were removed and transferred to the hatchery for weighing, counting and subsequent incubation of eggs and sac fry in 40-L aquaria until hatching. Growth was evaluated at primary and secondary nursery stages. In the secondary nursery stage, growth was studied in outdoor concrete tanks and indoor aquaria on a recirculating system. Genetic analysis was done using microsatellite markers. Thirteen primer pairs of O. niloticus were obtained from earlier work done by Lee and Kocher (1996) for use in amplification reactions. Amplification products were then subjected to electrophoresis on 7 % acrylamide gel followed by manual scoring of alleles. Results obtained on reproductive characteristics showed no significant differences (P> 0.05) among the four strains for relative fecundity (eggs/g female weight). However, significant differences among strains in spawning and incubation successes were observed. There were no significant differences in growth performance among the strains (P>0.05). However, significant growth differences were observed across production systems at the secondary nursery stage. Genetic analysis showed moderate overall strain differentiation with an overall FST value of 0.18. All four strains showed some heterozygote deficiency when tested for Hardy-Weinberg equilibrium with observed heterozygosities falling short of expected values.

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