GROWTH AND METAMORPHOSIS OF RANA-CATESBEIANA (SHAW) TADPOLES FED LIVEAND SUPPLEMENTARY FEED, USING TILAPIA, OREOCHROMIS-NILOTICUS (L), AS A BIOFERTILIZER

An experiment was conducted to compare growth and timing to metamorpho sis of bullfrog Rana catesbeiana (Shaw) tadpoles feeding on phytoplank ton and on supplementary feed. Three interconnected, round, 4 m diamet er concrete tanks were used in the experiment. Tanks 1 and 2 were stoc ked with juvenile tilapia, Oreochromis niloticus (L.) to stimulate phy toplankton through faecal fertilization. A third tank remained without fish. Stage 25-Gosner bullfrog tadpoles were placed in 0.042 m(3) cag es at 1 l(-1). Experimental treatments consisted of: (1) tadpoles Feed ing solely on phytoplankton (P); (2) P + 13% body weight day(-1) (bw d ay(-1)) supplementary feeding (SF); (3) P + 9.75% bw day(-1) SF; (4) P + 6.5% bw day(-1) SF; (5) P + 3.25% bw day(-1) SF; and (6) tadpoles f eeding solely on supplementary feed at 13% bw day(-1). Final weight wa s lowest in those organisms feeding exclusively on supplementary feed, followed by those feeding on phytoplankton. Treatments 2 and 3 showed the highest weight (3.65 and 3.64 g, respectively), After 70 days, 50 % of the tadpoles in treatment 4 (6.5% bw day(-1)) reached metamorphic climax, followed by treatment 5 (33%), Only 8% of tadpoles feeding ex clusively on live food reached metamorphosis. It is concluded that in the presence of abundant phytoplankton, it is possible to reduce up to 50% of the standard supplementary feeding rate and still have normal growth and metamorphosis. Tilapia represents a good alternative for bi ofertilization.