Growth Performance of Genetically Improved Farmed Tilapia in Polyculture With Indian Major Carps

Abstract

Genetically improved farmed tilapia, usually called GIFT, are often recommended as an addition to pond polyculture of the Indian major carps, catla, rohu and mrigal, on the argument that a fast-growing omnivore will use food niches the carps leave open. This narrative review asks how far published work supports that argument and what can fairly be said about the growth of GIFT in such ponds. It draws on literature on the breeding history of the strain, the feeding habits of the species involved, pond nutrient dynamics, stocking and species interactions, and the environmental debate over introduced tilapias, and it reports no new data. The pattern that emerges is conditional. Niche separation is real but incomplete, so competition for natural food is most likely where fertilisation or feeding is light and tilapia are stocked heavily. Growth reported for one stocking ratio, pond and season travels poorly to another, and pond-to-pond variation is often as large as the treatment difference. Claims of genetic gain across generations depend on contemporary comparisons and on the test environment, and a gain measured in one system need not be reproduced in another. Escape and establishment risks differ by region and deserve separate assessment. The review ends with a list of what a decisive polyculture trial should report.