Author(s): Thuy-Yen Duong, Thanh-Tuan Nguyen and Thanh-Liem Pham

Abstract: Morphological differences among two cultured and three wild bighead catfish (Clarias macrocephalus) populations, and introduced North African catfish (Clarias gariepinus) and hybrids (C. macrocephalus x C. gariepinus) collected in the Mekong Delta, Viet Nam, were assessed using five meristic and 21 morphometric measurements. Wild and cultured C. macrocephalus differed significantly at 19 of 21 morphometric traits (P<0.01), indicating high their phenotypic plasticity between natural and captive conditions. C. macrocephalus differed from C. gariepinus and hybrids in the number of gill rakers on the first branchial arch and for all morphometric traits (P<0.01). Principle component analyses revealed that occipital process size, head size, the distance from dorsal to caudal fins (DDCF), and fin lengths were particularly important to within-, between-species variation and to hybrid identification. Hybrids exhibited intermediate phenotypes relative to the two parental species in most of meristic and morphometric parameters, except DDCF comparable to C. macrocephalus and the shape of the occipital process similar to C. gariepinus. Discriminant analysis correctly classified 97.5 and 99.0% individuals as cultured and wild C. macrocephalus, 80.0% as C. gariepinus, and their hybrids with 95.7% confidence. Misclassifications were found between cultured and wild bighead catfish, and between C. gariepinus and hybrids. Results from this study can be used to distinguish F1 hybrid and cultured bighead catfish from wild individuals.

Pages: 233-240  |  1753 Views  322 Downloads

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