Biological performance of African Catfish (Clarias gariepinus) cultured in recirculating system in Ibadan A.O. Akinwole * , E.O. Faturoti Department of Wildlife and Fisheries Management, University of Ibadan, Nigeria Received 23 April 2005; accepted 25 May 2006 Abstract This study reports the biological performance of the African Catfish (Clarias gariepinus) in commercial recirculating systems in Ibadan, Nigeria. Water temperature recorded in rearing tanks ranged from 23 to 25 8C in fingerlings systems, 23–26 8C in juvenile system and 22–28 8C in grow-out rearing tanks. SS, DO, and NH 3 -N concentration in rearing tanks are within tolerable range for fingerlings and juvenile systems. DO levels fell as low as 2.0 mg/l while SS rose to as much as 36 mg/l in grow-out systems. Fish mortality had positive significant correlation ( p < 0.05) with nitrite concentration in cultured water (r = 0.88). The facilities operated at a mean density of 98.1 and 176.6 kg/m 3 of juvenile and adult fish respectively. Density was not significantly different from one facility to another ( p > 0.05). Stocking densities are 20,000–31,000; 6000–9000 and 150–300 fish/m 3 , while survival rates varies from 75 to 80% for fingerlings, 75–93% for juveniles and 77–88% for adult fish. Feed conversion ratio ranged from 0.60 to 0.78 for fingerlings, 1.01–2.08 for juveniles and 1.15–1.68 for adult fish while mean harvest weight for fingerling, juvenile and adult fish were 4.2, 11.2 and 981.0 g reared on the average for 28, 30 and 154 days, respectively. # 2006 Elsevier B.V. All rights reserved. Keywords: African Catfish; Recirculation; Fish production; Ibadan; Growth parameters 1. Introduction The African Catfish (Clarias gariepinus) is choice food fish species in Nigeria. It commands high demand from consumers and is mostly preferred by food fish aquaculturists. This is due to the ideal characteristics of this species (Eding and Kamstra, 2001), which includes high growth rate at high stocking densities, a high food conversion, good meat quality and smoking character- istics as well as year round production. Fish culture production in Nigeria includes lake stocking and production in ponds, cages and tanks (Ita, 1985). Pond culture is the most prevalent. Virtually all aspects of pond culture of African Catfish (C. gariepinus) in Nigeria has been developed and documented to ensure profitable production of the species. The appreciable quantity of water and large expanse of land required for pond culture has however limited the expansion of African Catfish culture in Nigeria. Intensive culture of finfishes in recirculating aqua- culture system (RAS), a production technique that reuses fish culture water more than once, thereby saving space and water requirement for fish culture, has been adopted to culture African Catfish (C. gariepinus) in Europe and America. Reports by Eding and Kamstra (2001) confirm that RAS has been adopted to successfully culture the African Catfish (C. gariepinus) at full commercial scale in Denmark and The Nether- lands. www.elsevier.com/locate/aqua-online Aquacultural Engineering 36 (2007) 18–23 * Corresponding author. Tel.: +234 8033600554; fax: +234 28103043. E-mail address: haayor@yahoo.com (A.O. Akinwole). 0144-8609/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaeng.2006.05.001