Growth Rate and Disease Resistance of Inbreds and Novel Intra-specific Crossbreds Larva of Clarias gariepinus (Burchell, 1822) in Response to Pseudomonas aeruginosa Challenge

Aim: To assess the differences in survival rate and Growth Rate (GR) in larva of novel inbred (CC) and crossbred (CS and SC) genotypes of C. gariepinus in response to P. aeruginosa disease challenge, in order to explore their potentials for improved aquaculture.

Study Design: Completely Randomized Block Design.

Place and Duration of Study: Department of Aquaculture and Fisheries Management, University of Ibadan, Nigeria, between June and November, 2015.

Methodology: Sixty individuals of four weeks old C. gariepinus inbred-CC (individuals not possessing serration at anterior portions of both sides’ pectoral spine-C) and SS (Individuals possessing the serrations-S) and crossbred-SC (maternal-S x paternal-C) and CS (maternal-C x paternal-S) strains were immersed in 500 ml water containing 0.01ml of 2.56x107 cfu/ml P. aeruginosa inoculums for 30 minutes. Challenged and control treatments were reared in freshwater for two weeks. Specimens were monitored for clinical signs, survival (%) and growth rate during 2weeks post challenge rearing period.

Results: At P= .05, values of survival and growth rates were significantly different across genotypes as well as across control and challenged treatments of each genotype. Fish from challenged treatments were sluggish, lost appetite, and had hemorrhage. 100% challenged-SC and 20.62±1.15% challenged-CC died within 72 hours; during this period, all control treatments, challenged-CS and challenged-SS survived. At 2weeks, survival rates (%) were higher in control than challenged SC (37.5±17.7:0.00) and CC(77.5±3.5:25.0±5.5), but similar (100%) in SS and CS. GR was 0.02±0.00 in control-SC. GR were significantly higher in challenged compared to control in CC, SS and CS: 0.20±0.01: 0.01±0.00, 0.46±0.03: 0.26±0.01 and 1.05±0.12: 0.33±0.02 respectively.

Conclusion: Paternal serrated crossbreed (CS) of C. gariepinus tolerated P. aeruginosa infection with superior survival and growth rate, thus indicating high potential for aquaculture in the face of the disease challenge, while maternal serrated crossbreed (SC) was highly susceptible