Intraspecific morphological variation between cultured and wild Clarias gariepinus (Burchell) (Clariidae, Siluriformes) Shola G. Solomon, Victor T. Okomoda, Abel I. Ogbenyikwu Received – 24 August 2014/Accepted – 14 January 2015. Published online: 31 March 2015; ©Inland Fisheries Institute in Olsztyn, Poland Citation: Solomon S.G., Okomoda V.T., Ogbenyikwu A.I. 2015 – Intraspecific morphological variation between cultured and wild Clarias gariepinus (Burchell) (Clariidae, Siluriformes) – Arch. Pol. Fish. 23: 53-61. Abstract. This study was designed to evaluate morphological differences between cultured and wild African catfish, Clarias gariepinus (Burchell). Fish samples were collected from the lower Benue River (axis in Makurdi), while cultured fish were obtained from the University of Agriculture Makurdi research farm. The results revealed significant sex-related variation in the fish from different environments. Significant differences were observed in all morphometric parameters measured and in three of the five meristic counts recorded. Discriminant analysis and cluster analysis of morphometric parameters showed a high divergence among the populations, hence the tested fish samples were grouped into respective environments by sex. The meristic count, however, overlapped broadly showing no divergence among the populations. The morphometric differences between the cultured and wild African catfish could have been linked to genetic differences or environmental factors or a combination of both factors. Keywords: African catfish, Benue River, morphometric parameters, meristic count Introduction Morphometric and meristic morphological characters are used widely to identify fish stocks (Turan et al. 2004), and they remain the simplest, most direct methods of species identification. From previous stud- ies (Creech 1992, Mamuris et al. 1998, Bronte et al. 1999, Hockaday et al. 2000), it is understood that the analysis of phenotypic variation in morphometric or meristic characters is the most commonly used method to delineate stocks of fish. It has often been used in discrimination and classification studies by statistical techniques (Agnew 1988, Avsar 1994). De- spite the advent of techniques which directly examine biochemical or molecular genetic variation, these con- ventional methods continue to play an important role in stock identification even today (Swain and Foote 1999). Differences in the morphometric and meristic characters of a species from different regions can re- sult from differences in genotypes, environmental fac- tors operating on one genotype, or both of these acting together (Parish and Sharman 1958). While both morphometric and meristic characters respond to changes in environmental factors, their responses are different in some situations and can differ from spe- cies to species. The study of differences and variability in morphometric and meristic characters of fish stocks is important in phylogenetics and in providing infor- mation for subsequent studies on the genetic improve- ment of stocks. The African catfish, Clarias gariepinus (Burchell), is a species of great economic importance as it is the most cultured catfish in Africa and the third most cultured catfish species in the world ( Arch. Pol. Fish. (2015) 23: 53-61 DOI 10.1515/aopf-2015-0006 RESEARCH ARTICLE © Copyright by Stanis³aw Sakowicz Inland Fisheries Institute in Olsztyn. © 2015 Author(s). This is an open access article licensed under the Creative Commons Attribution-NonCommercial-NoDerivs License (http://creativecommons.org/licenses/by-nc-nd/3.0/). S.G. Solomon [+], V.T. Okomoda, A.I. Ogbenyikwu Department of Fisheries and Aquaculture University of Agriculture, Makurdi, Nigeria e-mail: solagabriel@yahoo.co.uk