Handling stress such as netting, crowding and subsequent air exposure are common practices during fish sorting, transportation and other aquaculture practices that could affect the growth and welfare of cultured fish species. Here, we examined the growth and behavioural response of Clarias gariepinus exposed to sub-lethal handling-related stress . 180 C. gariepinus (12.556±1.48 g) were exposed to sub-lethal h andling stress (crowding and air exposure) under laboratory conditions. The fish species were exposed to a control group (T1), netting plus 3 0 secs of crowding (T2 ), netting plus 6 0 secs of crowding (T3) , netting plus 30 secs of air exposure (T4), netting plus 60 secs of air exposure (T5) to simulate durations of handling -related stress in the aquaculture sector fortnightly in triplicates for 84-days culture period . Growth indices (weight gain (WG), specific growth rate (SGR) and Feed Conversion Ratio (FCR) were observed weekly. B ehavioural traits (latency to feed (LF) feed intake (FI), and aggression (agonistic behaviour (AB)) were monitored fortnightly. Statistical analyses were performed using the generalized linear models in the R statistical package.
The treatments affected (ꭓ2 = 91.541, df= 4 , p = 0.02) the growth parameters of the fish species with similar (p> 0.05) growth responses in T3 and T5. Fish in the control group grew better and SGR was similar (P>0.05) between treatments (Table 1) .
LF was significantly (p<0.05) different across the treatments (Fig 1) and FI was lowest (p<0.05) in T5 (Fig 2). AB was similar in T3, T4 and T5 (Fig 3) . The treatments applied did not result in mortality during the study.
In conclusion, handling-related stress altered the behavioural response of C. gariepinus with increased agonistic behaviour and reduced mean weight gain. Thus, the level of handling stress should be reduced during aquaculture activities to prevent repeated acute welfare impairment in these fish species.
Keywords: Air exposure, Crowding stress, Fish welfare, Fish handling, Netting stress