REPRODUCTIVE PERFORMANCE AND SEX RATIO OF NILE TILAPIA Oreochromis niloticus FED DIETARY Aspilia mossambicensis AND Azadirachta indica LEAF MEAL  

Imani Kapinga*, Samwel M. Limbu, Rashid A. Tamahtamah2, Nazael A. Madalla3, Wahabu H. Kimaro4
 
Tanzania Fisheries Research Institute, P.O. Box 475, Mwanza
University of Dar es Salaam, Department of Aquatic Sciences and Fisheries Technology, P.O. Box 35064, Dar es Salaam, Tanzania
kapingaimani@yahoo.co.uk  

Prolific breeding is a major setback for farming mixed sex Nile tilapia Oreochromis niloticus. Various techniques including the use of synthetic hormones have been proposed to overcome this challenge. However, most of the techniques are highly hampered by cost, skills requirement and health concerns which makes their application difficult especially to small scale fish farmers. Therefore, this calls for a need to search for natural agents as a safe and affordable alternative. The present study was conducted to investigate the effect of two medicinal plants, Wild sunflower Aspilia mossambicensis and Neem, Azadirachta indica on the reproductive performance and sex ratio of Oreochromis niloticus.

O. niloticus juveniles (41.5 ± 3.1g mean weight) were used for reproductive performance experiment. Experimental diets AMI, AM2, AM4, AM8 and AI1, AI2, AI4, AI8 were formulated by adding 1.0, 2.0, 4.0 and 8.0 grams of  A. mossambicensis and A. indica leaf meal respectively  to a kilogram of control diet (25% CP). Fish were then fed at a ratio of 3% body weight for 90 days. Reproductive performance was determined in terms of hatchlings count (HC), absolute fecundity (AF), relative fecundity (RF), gonadosomatic index (GSI) and histology of the gonads. On the other hand, two weeks old hatchlings were used for sex reversal experiment. Experimental diets were made by adding 40 grams of  A. mossambicensis and A. indica leaf meal to a kilogram of control diet. Fish were fed with experimental diets for 90 days, followed by control diet for the remaining 60 days at 20% of their body weight. Feeding was done two times a day (10.00 and 17.00 hours).

Results revealed significant (p < 0.05) decrease n HC, AF and RF of fish fed A. mossambicensis and A. indica leaf meal doses (Table 1) Accordingly, histological alteration of gonads was noticed in both males and female fed doses 4.0 and 8.0 g kg-1. On the other hand, the two plants significantly (p < 0.05) altered the 50:50 (males:females) sex ratio (SER) in favor of males (Figure 1). Findings indicate that A. indica and A. mossambicensis can control prolific breeding as well as reverse the sex of O. niloticus.