Evaluation of production characteristics of four strains of Nile tilapia Oreochromis niloticus and a red variety under two sets of intensive culture conditions
Type of Degreethesis
Fisheries and Allied Aquacultures
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The wide native range of Nile tilapia O. niloticus offers the possibility of genetic diversity within the species and variation among populations as to their suitability for aquaculture. But only a few populations have been evaluated as to their aquaculture potential and less in head to head comparisons. A series of trials were conducted at Auburn University to compare production characteristics of four populations of O. niloticus using two domesticated strains (Egypt and Ivory Coast) and two less domesticated strains (Sagana and Lake Victoria). In addition, a red variety of tilapia (Santa Fe) was also evaluated. In the first trial, the different strains were compared under high density conditions in an indoor recirculating system at a mean (±SD) temperature of 27.1 ± 2.8 oC and fed commercially available diets. Initial mean (±SD) standing crop (kg/m3) ranged from 2.1 ± 0.1 (Sagana) to 2.7 ± 0.1 (Egypt) for a 203 day culture period. No one strain showed a distinct production advantage during this period. Mean (±SD) percent (%) survival ranged from 81.7 ± 6.8 % for the Ivory coast line to 97.5 ± 5.5 % for the Egypt line. Mean (±SD) feed conversion ratios during this period ranged from 1.4 (± 0.1) to 1.6 (± 0.1). A second study compared the growth of manually-sexed males from the five tilapia strains in aerated 20 m2 outdoor static water tanks. Fish with an initial mean (±SD) weight (g) range from 94 ± 5.4 (Red) to 108 ± 6.9 (Egypt) were stocked on May 30, 2007 at 2 fish/m2 and fed twice daily to satiation a 36% protein floating commercial feed. After a 120-day culture period, yield, survival and feed conversion ratio were compared. There were no production differences among all Nile strains. Nile strains out-performed the Red variety in several traits. Mean (±SD) standing crop (kg/ha) at harvest was less for the Red strain and ranged from 9,508 ± 396 (Red) to 14,438 ± 779 (Sagana). There was a significant difference (P = 0.01) in mean (±SD) male average weight (g) of the two smaller strains of Lake Victoria (365 ± 37) and Ivory Coast (380 ± 20) when compared to the larger Sagana 473 ± 30. Mean (±SD) % survival ranged from 78.8 ± 13.9 (Red) to 98.3 ± 1.7 (Egypt). Mean (±SD) feed conversion ratios were 1.3 ± 0.2 (Ivory Coast), 1.3 ± 0.1 (Sagana) to 1.9 ± 0.1 (Red). A third study compared fish processing characteristics of the five tilapia strains. The fish (n = 25 per strain) were harvested, stored on ice (2 ± 0.25 hrs) and manually processed into fillets. Mean percent fillet dress-out and mean percent visceral fat were compared. The Ivory Coast had highest mean (±SD) % fillet dress-out (33.1 ± 2.1) and the Sagana had the lowest (29.6 ± 1.5). The Red variety had the highest mean (±) % visceral fat (2.3 ± 1.0) and the Sagana had the lowest (0.2 ± 0.4).