## 2 Materials and Methods
### Experiment 1 in Bukavu, Eastern Highlands DR Congo
#### 2.1.5 Sample Collection and Analyses  
Prior to the start of the experiment, a sample (1 kg) of each feed was collected for proximate analyses. In addition, two samples of 10 fish were randomly selected from initial fish group, killed with an overdose of clove oil and weighed to the nearest 0.01 g  
\begin{table}
\begin{tabular}{c c c} \hline
**Ingredients (\%)** & **Fishmeal-Based** & **Fishmeal-Free** & **Commercial Feed** \\ \hline Blood meal (cow) & 20.00 & 29.50 \\ Fishmeal (37.5\% CP) & 30.00 & 0.00 \\ Soybean (local, full-fat) & 20.00 & 24.00 \\ Cassava flour & 5.00 & 5.00 \\ Corn (7.5\% CP) & 7.50 & 6.50 \\ Distillers/brewers grain & 5.00 & 20.00 \\ Rice bran & 5.00 & 3.00 \\ Palm oil & 1.00 & 1.00 \\ Bone meal & 1.00 & 4.00 \\ Trace mineral premix a & 1.00 & 2.00 \\ Vitamin C & 1.00 & 1.00 \\ Vitamin premix a & 1.00 & 1.00 \\ DL-Methionine & 0.75 & 1.00 \\ L-Lysine & 0.75 & 1.00 \\ Palm kernel cake & 1.00 & 1.00 \\ TOTAL & 100.00 & 100.00 \\ Analyzed composition & & \\ Dry matter, dm (\%) & 89.84 & 92.37 & 91.28 \\ Crude protein (\% dm) & 28.52 & 22.66 & 26.95 \\ Ash (\% dm) & 8.22 & 12.08 & 13.45 \\ Total carbohydrate (\% dm) b & 52.46 & 54.60 & 48.65 \\ Crude lipid (\% dm) & 10.81 & 10.67 & 10.94 \\ Gross energy (kcal/100 g dm) & 447.33 & 379.98 & 444.23 \\ COST/kg (USD) c & 1.184 & 1.134 & 2.000 \\ \hline \end{tabular}  
* Mineral and vitamin premixes were purchased from a feed store in the market in Bukavu, and there were no indication on their composition. b Total carbohydrate calculated as 100-crude protein (\%)-ash (\%)-crude lipid (\%).
* The cost of the commercial feed was based on the purchase price, while the estimated cost of the formulated feeds did not take into account the costs related to ingredients sourcing, feed processing and transport.  
\end{table}
Table 1: Experiment 1 in Bukavu, eastern highlands DR Congo—composition of the commercial feed and the fishmeal-based and fishmeal-free feeds formulated using local ingredients fed Nile tilapia (_Oreochromis niloticus_) fry of the “Nyakabera” and “Lake Kivu” strains in Bukavu, DR Congo.  
and measured to the nearest 0.1 cm. These samples were then deep-frozen until further proximate analyses of the body composition.  
Every two weeks, fish from each hapa were weighed and measured individually to estimate growth and adjust feeding rates. The hapas were changed during sampling; the dirty hapas were replaced by clean ones to allow good water circulation in and out of the hapas, and the dirty ones were washed and used for the next sampling.  
At the end of the experiment, all fish from each hapa were harvested, counted and weighed individually to the nearest 0.01 g and measured to the nearest 0.1 cm. A pool of 10 fish was randomly collected from each hapa, killed with an overdose of clove oil, pooled and deep-frozen until later proximate analysis of the body composition. Five other fish were collected from each hapa, individually weighed, and their livers and gonads were collected and weighed for the calculation of the hepato- and gonads-somatic indexes.  
Data on the water quality parameters such as temperature, dissolved oxygen, pH, and Secchi disk transparency were collected on a daily basis throughout the experiment. The temperature was on average 22.9 \(\pm\) 1.2 at 9:00 AM, 24.9 \(\pm\) 1.4 at 12:00 PM, and 23.3 \(\pm\) 1.4 at 4:00 PM; the dissolved oxygen level at 12:00 PM was 7.7 \(\pm\) 0.8 mg L\({}^{-1}\); the pH at 12:00 PM was 7.8 \(\pm\) 0.7; and the water transparency was between 25 and 35 cm.