IOSR Journal of Pharmacy and Biological Sciences (IOSR-JPBS) e-ISSN: 2278-3008, p-ISSN:2319-7676. Volume 10, Issue 5 Ver. II (Sep - Oct. 2015), PP 78-82 www.iosrjournals.org DOI: 10.9790/3008-10527882 www.iosrjournals.org 78 | Page Comparison of Fitness Traits between Reciprocal Hybrids and Parentals of Clarias gariepinus (Burchell, 1822) and Heterobranchus bidorsalis (Geoffroy Saint-Hilaire, 1809) Ola-Oladimeji, F.A. 1 , 1 (Department of Zoology, Ekiti State University (EKSU), Ado-Ekiti, Nigeria). Abstract: This study determined the viability performance of the hybrids produced from the crosses between Clarias gariepinus and Heterobranchus bidorsalis. Crosses were carried out on the parents; ♀ C. gariepinus x ♂ C. gariepinus, ♀ H. bidorsalis x ♂ H. bidorsalis, and for the hybrids; ♀ C. gariepinus x ♂ H. bidorsalis and ♀ H. bidorsalis x ♂ C. gariepinus. Fitness characteristics for the parental and reciprocal crosses of the fish species were determined on 30 hatchlings, for the first four weeks. The average percentage survival of the hybrids derived from the crosses between ♀ C. gariepinus and ♂ H. bidorsalis were significantly higher (77.38±5.37%) than that of the parental progenies and the reciprocal hybrid progenies of ♀ H. bidorsalis and ♂ C. gariepinus with 71.25±3.20% at p<0.05. The study showed that hybridization between C. gariepinus and H. bidorsalis produced intermediate results between both parental crosses. Keywords: African catfish, hybridization, reciprocal crosses, fitness I. Introduction Fishes are one of the most important sources of high quality protein. [1] reported that they are widely used as food because of their nutrient values and even their muscle types. The importance of fish to humans cannot be overemphasised. However, in Nigeria and other developing countries, the production of fish is less than its consumption. Lack of quality fish seeds is one of the leading factors responsible for this. [2] reported that in the aggregate, these factors create “scarcity syndrome” and lead to situation where farmers are forced to wait for a long period before receiving fish seeds, sometimes abandoning ponds in the interim. Both natural and artificial selection as well as cross-breeding between stocks and replacement of one stock with another are typical methods of breed development worldwide [3]. Some work has been done on genetic improvement and hybridization between different Cichlid [4] and Clariid fishes [5-9]. The present study was undertaken for stock improvement of C. gariepinus through inter-generic hybridization with H. bidorsalis. II. Materials And Methods The broodstocks of C. gariepinus and H. bidorsalis were obtained from the Teaching and Research Farm: University of Agriculture, Abeokuta, Ogun State and Gureje Aquaculture Centre in Ile-Ife, Osun State, Nigeria, respectively. They were obtained from two different farms to prevent the incidence of in-breeding. The brood stocks were transported in a 50 litre- tank opened at the top to the Wet laboratory of the Department of Animal Sciences, Obafemi Awolowo University, Ile-Ife. They were kept at constant temperature of 25ºC in 1000-liter tank and were fed with 37% Crude Protein commercial feed (DURANTE®, Nigeria) three times daily. The water quality was maintained through proper monitoring and weekly replacement. They were fed for three months to allow for proper acclimatization and maturity before their utilization. Gravid females of C. gariepinus and H. bidorsalis were selected based on their swollen reddish genital papilla and a well-distended, swollen soft abdomen that oozed out eggs when gently pressed. Sexually matured males of C. gariepinus and H. bidorsalis were equally selected based on reddish pointed and vascularised urogenital papillae. Hypophysation of the specimens was carried out in the Department of Animal Sciences, Wet laboratory, Obafemi Awolowo University. The selected female broodstock of C. gariepinus and H. bidorsalis (1.0±0.6 kg) were kept separately in the hatchery for two days without feeding so that the alimentary tract was empty at the time of stripping. Sexually matured males of C. gariepinus and H. bidorsalis weighing 1.1±0.8 kg were selected and kept in different tanks of 50 litre capacity for two days prior to the time of sperm collection. Oocyte maturation and ovulation in the female fish of both species were induced with a single intramuscular injection of Ovaprim (R) (SYNDEL, Canada) at a dosage of 0.5ml/kg live weight and then left for 10-17 hr latency period depending on the catfish species. The female broodstock was carefully dried with a clean towel and tightly held at head and tail ends while the eggs were handstripped by pressing their abdomen into clean and dry petridishes. The eggs were fertilized with milt obtained from lacerated testes (and kept in physiological salt solution of 0.9%) by using