Widespread hybridization among species of Indian major carps in hatcheries, but not in the wild
Abstract:Twenty‐one allozyme loci in samples of wild‐caught and hatchery‐reared Indian major carps from Bangladesh were analysed. Bayesian model‐based clustering analysis revealed the presence of four taxa, corresponding to the three known species along with a fourth unknown taxon present in two hatchery samples. Individual admixture coefficients showed that 24% of all hatchery‐reared fishes were hybrids, whereas a single hybrid was observed in the wild‐caught samples. Only catla Catla catla× rohu Labeo rohita and mrigal Cirrhinus cirrhosus× rohu hybrids were observed, the vast majority of which were F1 hybrids, though five individuals represented putative backcrosses. Mitochondrial DNA analysis revealed that catla × rohu hybridization primarily involved catla males and rohu females, whereas mrigal × rohu hybrids primarily resulted from rohu males and mrigal females. Despite the high percentage of F1‐hybrids in hatchery samples, reproductive barriers among species have so far precluded widespread introgression. Continued hybridization may eventually lead to a breakdown of species barriers, thereby compromising the genetic integrity of the species in the wild, and leading to production losses in aquaculture.
Document Type: Regular Paper
Affiliations: 1: National Environmental Research Institute, Vejlsoevej 25, P. O. Box 314, DK-8600 Silkeborg, Denmark, 2: Department of Inland Fisheries, Danish Institute for Fisheries Research, Vejlsoevej 39, DK-8600 Silkeborg, Denmark and 3: Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh-2022, Bangladesh
Publication date: September 1, 2005