Research output

Conference Paper (in Formal Publication) ()

Growth and sexual development of 17 alpha testosterone and progesterone treated Nile tilapia (Oreochromis niloticus) reared in earthen ponds

MacIntosh D, Singh T, Little DC & Edwards P (1988) Growth and sexual development of 17 alpha testosterone and progesterone treated Nile tilapia (Oreochromis niloticus) reared in earthen ponds In: Pullin RSV, Bhukaswan T, Tonguthai K, Maclean JL (ed.) Second International Symposium on Tilapia in Aquaculture, Manila, Philippines: Metro, pp. 457-463.

Swim-up fry (average weight, 14 mg) were obtained from Oreochromis niloticus (Chitralada strain) held in concrete tanks. In experiment 1 (1985), fry were fed diets treated with 17 alpha-methyltestosterone (MT) or progesterone at 60 mg/kg for 40 days. Control fish were fed untreated diet. Fingerlings (average weight, 2.86 g) were subsequently stocked at 1/square m. in earthen ponds receiving septic tank slurry at 150 kg COD/ha/day and fine rice bran as supplementary feed for about 5 months. In experiment 2 (1986), similar procedures were followed but the fry were fed MT at 40 mg/kg for 40 days and pond stocking rates of 1,3,5 and 7 fingerlings/sq. m were compared. Individual size, sex and stage of maturity were determined. In experiment 1, the average individual size was greatest in the MT-treated group (263 g), compared with the untreated (232 g) and progesterone-treated fish (189 g). The final size of fish in experiment 2 decreased significantly (P0.05) with density, from an average of 249 g at 1 fish/meter square average of 249 g at 1 fish/square meter to 94 g at 5/square meter; however those stocked at 7/square meter gave the highest total biomass and were not significantly smaller (P0.05, mean weight, 88g) than the fish stocked at 5/square meter. Sex could not be determined by external morphology alone, but sexing on gross gonadal structure agreed well with subsequent histological examination. The percentages of male fish were: MT-treated, over 93%; progesterone-treated, 72% and untreated, 57%. All treatments included fish at various stages of maturity, from undifferentiated to fully mature gonads. In MT-treated fish, females commonly showed abnormal enlarged ovaries: egg bound or distented with fluid. Some males, particularly those fed the higher level of hormone (60 mg/kg) showed some testicular degeneration which lowered GSI [gonadosomatic indices] values.

EditorPullin RSV, Bhukaswan T, Tonguthai K, Maclean JL
AuthorsMacIntosh Donald, Singh T, Little David Colin, Edwards Peter
Title of seriesICLARM Conference Proceedings
Number in series15
Publication date1988
Place of publicationManila, Philippines
ISSN of series 0115-4435
ISBN 971-1022-60
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