Note: 8KR2 has been cancelled. See Third Addendum to the Eighth Work Plan

This describes the collaboration of the Africa CRSP project with an activity submitted by R. Phelps et at. as Study A in their proposal "Monosex Tilapia Production through Androgenesis."

Objective
Significance
Collaborative Arrangements
Experimental Design
Identification of Deliverables
Schedule
References

Objective

Determine the variability in sex ratios from pair mating of tilapia for the strain present at Sagana station.

Significance

The few populations of O. niloticus that have been studied give mean population sex ratios of 50:50 that would be expected from a XX:XY inheritance pattern but with considerable variation from 50:50 when individual pairs are considered. The source of this variation is unknown and maybe a characteristic of the species or only the strain which was evaluated. According to Seyoum and Kornfield (1992), there are 3 distinct subspecies of O. niloticus present in Kenya: O. niloticus eduardianus, O. niloticus baringoensis, and O. niloticus vulcani. The latter is presently cultured at Sagana Station in Kenya. This subspecies will be one of the five that Phelps et al. will examine for sex ratio inheritance.

Collaborative Arrangements

The Africa project will contribute the facilities and routine labor for the on-site work at Sagana only. Other costs of the project will be supported by Phelps et al. Contacts will be made to facilitate collection of the other two strains available in Kenya.

Experimental Design

Site: Sagana station, Kenya.

Pond Facilities: One large pond and hapas.

Procedure: A minimum of 50 pair spawns of non-hormone-treated O. niloticus vulcani will be made in outdoor hapas. Fry will collected and reared as individual sets to a minimum of 5 cm in length. The sex ratio of each set of progeny will be determined by examining the gonads of a minimum of 100 fish per set of progeny.

Sex ratio data from each spawn would be analyzed by Chi square to determine whether it differs from the expected 50:50. The frequency distribution of all spawns within this strain would also be determined and compared across other strains that will be examined in the larger study. If this strain conforms closely to an XX:XY inheritance pattern, live fry will be shipped to Auburn for further study, possibly to be used in a "YY" breeding program to be supported by the Phelps et al. work plan.

Null Hypothesis: All strains of tilapia have similar variations in sex ratios.

Identification of Deliverables

Strains of O. niloticus with the minimum variation in sex ratios between pairs will be identified for use in breeding studies.

Schedule

Start upon arrival (Nov. 1996), end one year later.

Final Report Submittal: Results will be incorporated into the report by Phelps et al. Final report for this strain by March 1998.

References

Seyoum, S. and I. Kornfield 1992. Identification of the subspecies of Oreochromis niloticus (Pisces: Cichlidae) using restriction endonuclease analysis of mitochondrial DNA. Aquaculture, 102 29-42.