2.3 Fish sampling
Fish were collected using the a Fisheries Independent (FI) sampling methods with fish gears that include gill netting materials ranging from 2.5 to 8 cm mesh size and 3 m deep and 30 m longs; two double ended fyke nets made from 20 mm stretched multifilament netting with 75 cm D-ends separated by an 8 m leader; an LR-24 electrofisher-Smith-Root with 400 watt electrical output; and a beach seine net of 25 m long, and 3 m deep. Fyke and gill net gears were deployed along the banks of the slow flowing waters where boat access was not restricted by fish weirs or fallen tree and inspected in the morning (6 am) and afternoon (17 pm) for period of 2 months, and displayed for 24 hours. Electric fishing and seining were conducted during daytime over three days per week within each sampling point. The fishes caught from five aforementioned distinct habitats at different times of the day (6 a.m., 12 afternoon and 5 p.m. to comprehensively understand effective feeding period of the day) (Table 1), however, effort was limited by the amount of suitable habitat for each gear type and restricted to areas where it was deemed safe to operate. Because variations in the feeding based on feed item of the fishes depend on body size and developmental stages; we selected individuals of each species that corresponded to the adult size class interval or rather those in the same size category as both species attain similar growth size. The specimens were then measured (total length [TL] ± 1.0 mm) and weighed (wet mass ± 0.1 g). The species selected were the exotic O. niloticus (n = 201) and nativeC. rendalli ( N=166) for dietary examination. The selection was based on the most abundant fish species caught in the size class (<50, 51-100, 101-150 mm TL) in the river (capture frequency >10%) according to Eloranta et al. (2015).