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Evaluation of Reproductive and Growth Performance and Microsatellite Variability of Four Strains of Nile Tilapia (Oreochromis niloticus, L.)

(abstract of George Osure's M.S. thesis)

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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Congratulations to George Owiti Osure for the successful defense of his Master's thesis in September 2003 at Auburn University, Auburn, Alabama. Osure was first featured in Aquanews in the Graduate Student Profile (Vol. 18 No. ­ Fall 2003). His accomplishments include receiving the Best M.S. Student Award given annually by the Department of Fisheries and Allied Aquaculture. Osure's major professor was CRSP Principal Investigator Ron Phelps at Auburn. Osure is especially keen to see aquaculture realize its potential to benefit Kenya socially and environmentally. Once back in Kenya, he will resume working at the Kenya Department of Fisheries and aims to obtain funding for a Ph.D. project. We wish him every success with his future career in aquaculture.

Graduate's
Corner
Aquaculture CRSP Awards

The Aquaculture CRSP is pleased to announce the awardees in the Pre-Conference World Aquaculutre Society (WAS) 2004 Awards for Aquaculture CRSP Students and Pre-Conference WAS 2004 Awards for Aquaculture CRSP Professionals. Seven student and three professional awards were given. Student eligibility criteria included involvement in a CRSP project since 1996, the beginning of the current grant, with preference given to students presently pursuing a degree. Professional eligibility criteria included CRSP involvement, with preference given to those presenting direct impacts of CRSP work and those presenting
value-added research with CRSP work as its foundation. Awardeesą names are listed below, along with their abstract entry title to 2004 WAS.
Congratulations to all.

Student Awards Recipients

Fred Chu-Koo, Southern Illinois University, Carbondale—Christopher Kohler, Major Professor—for:
Chu-Koo, F.W., C. Kohler, W. Camargo, L. Rodriguez, and F. Alcantara. Seed Dispersal by Frugivorous Amazonian Fish.
Eddie Boy T. Jimenez, Central Luzon State University, Philippines—Remedios Bolivar, Major Professor—for:
Jimenez, E.B.T., R. Bolivar, and C.
Brown. Cost of Containment Option in Semi-Intensive Tilapia Culture: Evaluation of Alternate Day Feeding Strategy.
Maria Esther Palacios, The Ohio State University—Konrad Dabrowski, Major Professor—for:
Ostaszewska, T., M.E. Palacios, and K. Dabrowski. Growth and Morphological Changes in Digestive Tract of Rainbow Trout and Paku Due to Fish Meal Protein Replacement with Soybean Products.
Gustavo Rodriguez, The Ohio State University—Konrad Dabrowski, Major Professor—for:
Rodriguez, G., K.J. Lee, W. Contreras, K. Park, and K. Dabrowski. Evaluation of
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