International Journal of Aquaculture, 2018, Vol.8, No.9, 65-72
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2 Conclusions and Recommendations
The result of the present study revealed that
O. niloticus
populations from Lake Chamo showed better growth
performance compared to those from Lake Tana and Lake Hashengie. However, the final mean weight, daily
growth rate and Specific Growth Rate in the current experiment were lower compared with the results from
similar studies. This raises a question on the quality of the feed used particularly on its digestibility and the use of
mixed sex for the experiment that calls for further study. Based on our result
O. niloticus
from Lake Chamo can
be used for tilapia stocking and for further strain selection programs.
3 Materials and Methods
The study was conducted at National Fisheries and Aquatic Life Research Center (NFALRC), Sebeta, Ethiopia
(8°55.076’N; 38°38.161’E), located 24 km South-West of Addis Ababa at an altitude of 2220 m above sea level.
The experiment was designed to evaluate growth variations among
O. niloticus
populations collected from
geographically isolated lakes: Chamo, Tana and Hashengie and were reared separately in earthen ponds at
NFALRC.
O. niloticus
fingerlings from the first generation of each parents hatched at NFALRC research ponds
here after called CH
O.n
; TA
O.n
and HA
O.n
, respectively were used for the experiment. Concrete ponds (25 m
2
each) were dried and limed with quick lime and fertilized using manure. Uniform sized fingerlings obtained from
the parents of each lake were stocked into experimental ponds with a stocking density of 2 fish/m
2
. After two
weeks of acclimatization, 50 fingerlings with mean total body weight of 16.7, 15 and 16.9 g for CH
O.n
, TA
O.n
and HA
O.n
, respectively were stocked randomly in three replicates. The experiment was conducted for 120 days
and the experimental animals were fed formulated diets from locally available agro-industrial bi-products
(Brewery waste, Wheat bran and Noug cake) supplemented with commercial (Deutsche Vilomix GmbH) vitamin
and mineral premix at 2% inclusion level (Chapman, 1992). The formulated feeds were minced in pelleted form
using meat grinder. We used two different mesh size sieves, 2 mm mesh size sieve used for first and second
months and 3 mm mesh size sieve for the later months. Percent inclusion and proximate composition of the feed
ingredients and vitamins and mineral premix are presented in Table 4 and Table 5. Proximate analysis of the feeds
was carried out in triplicates as described in AOAC (1990). We used micro-Kjeldhal method for crude protein
analysis and Ether extraction method for fat.
Table 4 Percent inclusion and proximate composition (g/100 g feed) of feed ingredients
Feed ingredients
Inclusion (%)
Wheat bran
9
Brewery waste
35
Noug seed cake
54
Additive (Premix)
2
Percentage composition (g/100 g feed)
Dry matter
50.8
Carbohydrate
31.3
Crude protein
29
Crude fiber
22
Lipid
4.8
Gross energy (kcal/100 g)
364.1
Protein energy ratio (g/kcal)
4.9
The fish were fed 5% of their body weight daily (half of the feed at 10:00 am and the remaining half at 4:00 pm).
The feed was delivered at the same position on a round feeding tray made of mosquito net to minimize wastage
through sinking. Water was flashed into the experimental ponds every 3
rd
day.
Biological data (Length-weight) was measured every 15 days by taking 50% of the fish stocked using seine net.
Total length and total weight were measured to the nearest one decimal centimeter and gram, respectively. The
