Effect of Pawpaw (Carica Papaya) Seed Meal on Sex Determination, Growth, and Survival, of Oreochromis mossambicus Fry

Abstract

The production of monosex tilapia populations is a potential and effective solution for the precocious breeding and indiscriminate spawning that occurs in mixed sex culture systems. This study investigated the possibility of using Carica papaya seed meal (PSM) to skew the sex ratio of sexually undifferentiated Oreochromis mossambicus fry. A total of 2160 fry were used in the study, and fish were allocated to 12 treatment groups in triplicate, with 60 fish per replicate. The experimental diets fed included a basal diet (BD), 60mg methyl testosterone/kg BD, and 5 treatment diets containing 10, 15, 20, 25 and 30g PSM/kg of the BD, respectively for 30 and 120 days. PSM was able to skew the sex ratio in favor of males, with the proportion of males to females increasing with an increase in PSM content of the diet. The highest percentage phenotypic males (77.8%) induced by the PSM was obtained among the groups that received 20g and 30g PSM/kg BD. The growth and survival rates of the fish were not influenced by any of the treatment diets. Fragmentation of ovarian nuclei, hypertrophy of interstitial cells, and vacuolization of hepatocytes were observed in the gonads and hepatic tissues. The study demonstrated that an inclusion level of 20g PSM/kg BD was effective in converting females to phenotypic males.