## 2 Materials and Methods
### Experiment 2 in Kinshusa, Western Lovlands of DR Congo  
#### 2.2.1 Experiment Design, Facility and Fish  
The experiment was conducted using a completely randomized design. The experimental treatments included three strains of Nile tilapia, namely the GIFT-derived RATALBI strain found at the fish station of the non-governmental organization RATALBI, the GIFT-derived Congo Futur strain obtained from the commercial farm Cap Congo Piscitulture, and the Thiang-derived strain originally imported from Belgium and available at the RATALBI fish station. Information from the farms indicated that the GIFT-derived Congo Futur and the GIFT-RATALBI strains of Nile tilapia used in this experiment were obtained in 2017 from the same commercial fish farm in Lubbamshi which sourced its broodish from Chirundu, Southern Province, in Zambia. The GIFT-RATALBI strain was directly introduced to the station of the RATALBI Piscitulture where the experiment was conducted, while the GIFT-derived Congo Futur strain transited to the Cap Congo Piscitulture where they spent two years before being moved to the RATALBI Piscitulture for this experiment. During the two years that preceded the experiment, the GIFT-derived Congo Futur strain was isolated from any other strain available at the Cap Congo Pisciculture in Kinshasa and was fed balanced commercial farm-made floating feeds following a good feeding program, but did not undergo any planned breeding or genetic improvement program. During the same period, the GIFT-RATALBI strain was administered a less strict management protocol, and was fed low-quality farm-made powder or bullet feeds. In addition, it is possible that the GIFT-RATALBI strain was mixed and bred with another unknown Nile tilapia strain available at the RATALBI Piscitulture. As such, the GIFT-derived stain available at the Cap Congo Pisciculture (GIFT-Congo Futur) and the GIFT-derived strain available at the RATALBI Pisciculture (GIFT-RATALBI) are considered two distinct strains in the present experiment.  
Little information is available on the precise origin of the Thiang-derived strain of Nile tilapia that was introduced to the RATALBI Pisciculture following importation from Belgium between 1985 and 1995 (precise dates not available). Over the years, no systematic measures were put in place to effectively control inbreeding within the imported Thiang-derived strain, and between this strain and any other known or unknown stock of fish available at the RATALBI Pisciculture. Throughout the following text, these strains will be referred to as GIFT-Congo Futur, GIFT-RATALBI and Tihange, respectively.  
Each treatment was applied in triplicate. Nine experimental haps (experimental units) of 1.9 \(\times\) 2.6 \(\times\) 0.8 m (5.0 m\({}^{2}\) surface) each, with 1 mm mesh size were installed in a single large pond. The pond preparation and fertilization as well as the fish stocking methods were the same as in experiment 1, conducted in the eastern part of DR Congo. Each hapa was stocked at a density of 3 fish/m\({}^{2}\) of hapa. The initial average body weights \(\pm\) standard deviation of the fish were 19.12 \(\pm\) 0.06 g, 18.96 \(\pm\) 0.11 g and 19.00 \(\pm\) 0.08 g for the Tihange, GIFT-RATALBI and GIFT-Congo Futur, respectively. The experiment lasted 84 days (12 weeks).