Abstract
Five introduced strains of Nile tilapia (Oreochromis niloticus) were tested for growth performance both in fresh- and brackish-water (2 salinity units) environments for 56 days. The BIG NIN, GIFT, Chitralada, “Ruvu Farm” and Silver YY strains with initial mean average weight (± standard error) of 96.4 ± 6.90 g, 104.1 ± 7.19 g, 137.2 ± 7.21 g, 53.2 ± 6.98 g and 95.3 ± 7.11 g, respectively were used. Individuals were tagged and pooled in hapas (12 m × 8.5 m × 2 m each), aligned into different ponds (20 m × 20 m each). Stocking density of 5 fish/m2 and 350 g/kg crude protein diet were used. Overall, the average weight gain for GIFT strain was 7.5%, 32%, 45% and 86.5% higher than BIG NIN, Chitralada, “Ruvu Farm” and Silver YY strains, respectively, across both environments. All strains performed significantly better (p < 0.05) when reared in brackish-water than their respective counterparts in freshwater, except for the BIG NIN strain. The morphometric correlations for all strains in both environments ranged from moderate (0.50) to strong positive (0.92). The GIFT strain demonstrated superior growth and genotype by environment interaction was weak and not important to be prioritized in breeding programs.
Highlights
Tilapias, especially Nile tilapia (Oreochromis niloticus), have the potential to become the leading farmed fish species in the w orld[1]
Number of deaths recorded during hormonal sex reversal trial were 8, 77, 96, 48 and 192 for BIG NIN, Genetic Improvement of Farmed Tilapias” (GIFT), “Ruvu Farm”, Chitralada and Silver YY, respectively
We provide clear evidence that the growth performance of all five introduced strains of Nile tilapia (O. niloticus) imported from Thailand (BIG NIN, GIFT and Chitralada), Uganda (“Ruvu Farm”) and the Netherlands (Silver YY) showed clear differences between both locations and lines
Summary
Especially Nile tilapia (Oreochromis niloticus), have the potential to become the leading farmed fish species in the w orld[1]. There are some Asian local tilapia stocks with no genetic improvement but that are widely farmed with an excellent reputation and well-proven track record among aqua-farmers These include; the red tilapia which have mainly originated through the interspecific cross of O. mossambicus and O. niloticus[18,19] and Chitralada strain from small founder population of O. niloticus[3]. A number of farmed tilapia strains have been subjected to hormonal sex reversal, interspecific hybridization (cross-breeding) and genetically male tilapia (GMT) or YY super male technologies The latter were meant to help avoid problems related to early sexual maturation, unwanted reproduction, and overpopulation in a fish p ond[20,21]. For sustainable and profitable aquaculture, continuous evaluation of both GIFT and local breeds should be prioritized
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