Can Tho University Journal of Science Vol. 13, No. 3 (2021): 1-8 1 DOI: 10.22144/ctu.jen.2021.034 Growth and survival performance of G2 crossbreeds from two strains of bighead catfish (Clarias macrocephalus) Dedan Karanja Njihia 1 and Duong Thuy Yen 2* 1 International Master Program in Aquaculture, Course 3 (2018-2020), Can Tho University, Viet Nam 2 College of Aquaculture and Fisheries, Can Tho University, Viet Nam *Correspondence: Duong Thuy Yen (email: thuyyen@ctu.edu.vn) Article info. ABSTRACT Received 22 Aug 2020 Revised 31 Jan 2021 Accepted 20 Nov 2021 The development of bighead catfish (Clarias macrocephalus) aquaculture in Viet Nam has been constrained by the slow growth performance in the domesticated strain. Crossbreeding can be a solution to improve fish production. This study was aimed to evaluate the growth and survival performance of the second generation (G2) fingerlings crossbreeds (CMCT and CTCM) from two bighead catfish strains (wild Ca Mau, CM, and domesticated Can Tho, CT) compared to offspring from their original strains (G0-CT and G0-CM) and G1 crossbreeds (♀CM × ♂CT and ♀CT × ♂CM). The larvae were reared in 50-L tanks (3 to 5 replications) with the density of 1,000 individuals/tank and fed with Moina and artificial feed (40% protein). After 40 days of rearing, the fish grew differently among crosses (P<0.05). In which, the two best-growth groups included CM×CT crossbreeds (body weight of 1,114 mg and length of 4.55 cm) and pure crossbred line CTCM (1,050 mg and 4.51cm, respectively). The CTCM group was recorded the highest survival rate (37.8%) while G0-CT was the lowest (27.2%); however, the difference in survival was not significant (P>0.05). The performance of these crossbreeds should be investigated further at the grow-out stage to see whether crossbreeding between wild and cultured strains of bighead catfish may be used in practice to increase bighead catfish production. Keywords Bighead catfish, crossbreeding, genetic improvement, growth, larval rearing 1. INTRODUCTION Catfishes in the genus Clarias are widely distributed in subtropical and tropical areas of Asia and Africa (Teugels & Adriaens, 2003). In Viet Nam for instance, Clarias catfish is one of the commercially important aquaculture fish groups consisting of C. macrocephalus, C. gariepinus, C. fuscus, C. batrachus, and one hybrid C. macrocephalus (Cm) x C. gariepinus (Cg) (Lenonnand et al., 1998). Among the four Clarias species, bighead catfish (C. macrocephalus) is a popular species with a high economic value (Hien et al., 2018). It has long been an important target for aquaculture in Southeast Asia (Carreon et al., 1976; Na-Nakorn et al., 1995). Bighead catfish is however not so popular in intensive farming due to low disease resistance and a slow growth rate (FAO, 2010). While its hybrid catfish (Cm x Cg) that exhibits fast growth rate, high tolerances to environmental conditions, and resistance to diseases has been cultured in many provinces in Viet Nam (Duong et al., 2017). Native bighead catfish remains to be the most preferred