An evaluation of radiography in studies of gastric evacuation in African catfish fingerlings

Groups of 3-4 g African catfish (Clarias gariepinus Burchell, 1822; Family: Clariidae) were offered feeds of two types in three combinations: feed wit h a radio-opaque marker (Ballotini, 0.16-0.25 mm), feed without marker and a 50:50 mixture of marked and unmarked feeds. Stomach contents were estimat ed by X-radiography and gastrectomy just after meal termination and at diff erent time intervals (4, 8, 12, 16, 20, 24, 32, 40 and 48 h). There were no significant differences among treatment groups confirming that there was n o effect of the marker on feed preference and evacuation rate. Estimations of gastric evacuation rate calculated from gastrectomy and by X-ray samplin g were not significantly different. Therefore, gastric evacuation rate of A frican catfish can be accurately estimated by feeding marked feed and then using X-radiography to monitor feed passage through the gut.