Interim Work Plan, Africa Study 7
Edwin S. Smith and Ronald P. Phelps
Department of Fisheries and Allied Aquacultures
Auburn, Alabama, USA
(Printed as Submitted)
Tilapia are cultivated in Africa, southern Asia and Central and South America. The "red" tilapia (Oreochromis spp.) has greater acceptance among some consumers, but "normal" colored fish showed superior growth compared to red colored fish. This research compares Nile tilapia and "red" tilapia as relates to the reproductive efficiency of adults and growth, survival, and response to sex reversal of fry.
Sex reversal involves feeding a feed that has been treated with a male hormone to fry before the primal gonadal cells of females have differentiated into ovarian tissue. The hormone-treated feed used for sex reversal is generally stored under refrigeration. Incorporated in this research is an analysis of the shelf life at ambient tropical temperatures of the hormone-treated feed used for sex reversal. The following is a preliminary report summarizing methods and results without statistical analysis. All research was conducted at "El Carao" Aquaculture Station in Comayagua, Honduras.
Materials and Methods
Experimental design and procedure were conducted in the same manner as the above study except for the following. Feeds for this experiment were taken out of the freezer at their designated times and placed in a refrigerator at 4°C or "on the shelf" at tropical ambient temperature (28°C +/- 1.5°C). Feed storage times were: a) zero months in the refrigerator - 26 days on the shelf, b) zero months in the refrigerator - seven days on the shelf, c) zero months in the refrigerator - zero days on the shelf, d) two months in the refrigerator - 26 days on the shelf, e) two months in the refrigerator - seven days on the shelf, and f) two months in the refrigerator - zero days on the shelf. Fry were fed daily for 14, 21, or 28 days. These studies began on February 7 and finished on August 31.
Preliminary results are summarized in Table 1.
Table 1 (31 K file). Summary of the growth
and efficiency of sex reversal of Nile tilapia fed hormone-treated feed
stored under different storage regimes.