Identification of Indian Major Carps (Catla catla, Labeo rohita and Cirrhinus cirrhosus) and Their Hybrids by Phenotypic Traits, Allozymes and Food Habits

A study was carried out to identify pure and hybrid fingerlings of Indian major carps, catla, rohu and mrigal by analysing phenotypic traits, allozymes and food habits. Pure (catla, rohu, mrigal) and hybrid (rohu x catla, mrigal x catla and rohu x mrigal) fry were produced by artificial insemination. A total of eight phenotypic traits (body shape, body colour, fin colour, head size, mouth shape, eye colour, lateral line, scale shape) were examined where five were found to be intermediate in hybrids relative to the parental species. Four allozyme markers, lactate dehydrogenase (LDH), malate dehydrogenase (MDH), phosphoglucomutase (PGM) and glucosephosphate isomerase (GPI) were used to identify them genetically. GPI was found to be diagnostic at one of two loci revealing three alleles. Gut content was analysed to estimate feeding relationship between pure and hybrids. Among the pure fingerlings, catla and rohu were found to consume a wide variety of planktons while mrigal consumed both planktons and benthos. On the other hand, all hybrids consumed both planktonic and benthic groups. The extent of dietary overlap between hybrid and their parental species revealed a very high competition for food ranging from 0.96 between mrigal x catla and both parental species to 0.98 between rohu x catla and rohu.