Growth and production performance of red tilapia and Nile tilapia (Oreochromis niloticus Lin.) under low-input culture system

Comparative production potential of red tilapia (a mutant hybrid of Oreochromis mossambicus) and Nile tilapia (Oreochromis niloticus) under low-input aquaculture was studied in six ponds of 360 m² each with an average water depth of 90 cm. Three ponds were stocked with fingerlings of O. niloticus (average weight 11.4±3.48 g) while three other ponds were stocked with red tilapia (average weight 10.72±2.5 g) at a density of 20,000 fingerlings/ha. Supplementary feed consisting of rice bran was given daily at 4-6% of standing biomass. Ponds were fertilized at fortnightly intervals with cattle manure 750 kg/ ha. After six months of rearing, gross fish productions of 3,218 and 3,017 kg/ha were obtained from O. niloticus and red tilapia ponds, respectively. Of this, table size fish (>80 g in size) production amounted to 2,366 and 2,823 kg/ha from O. niloticus and red tilapia culture, respectively. Analysis of cost and benefits showed higher benefit from red tilapia culture.

Effects of the quick and slow freezing on the quality of Nile Tilapia fillets (Oreochromis niloticus) and Red Tilapia fillets (O. niloticus and Tilapia mosambicus)

In this study, quality of fresh, slow frozen and quick frozen tilapia fillets and its changes during storage at -18C° were investigated. For preparation the samples, fresh tilapia fillets were frozen by slow and quick frozen methods. Slow frozen samples were prepared by storing the packed fillets directly in the -18 C°. The sprila freezing tunle with -30C° was also used for preparation the quick frozen sample. The quick frozen samples were then stored at -18C°for six months. Proximate composition, fatty acid profiles, TBA, PV, TVN, Total cuont, Drip loss, and sensory evaluation of the samples were determined in every month. Scanning Electron Microscopy (SEM) was used for study on the effects of the frozen condition on the microstructure of the fillets. Results indicated that two different frozen methods had significantly different effects on the quality of the fillets. Most of the proximate composition (protein, moistre and fat) reduced during the storage. Quick frozen filets had significantly (P<0.05) lower reduction than slow frozen samples. All of the chemical quality indexes (PV, TBA, and TVN) increased during the storage as compered to the fresh samples. In these paramethers, the slow freezing had higher changes than quick freezing metods (P<0.05). The microbial properties of the samples showed decrese during the storage. Lower amont of total cuont was observed at the end of the storage time in the quick frozen samples than slow frozen once (P<0.05). The large changes in the fatty acid profiles of the sample were fond in all samples. During the storage SFA and MUF of the samples increased however, the PUFA decresed. A lower change was obseved in the quick frozen samples than slow frozen samples (P<0.05). Drip loss was increased in both frozen samples during the storage period. The percentage of the drip in the slow frozen samples was significantly higer than quick frozen samples (P<0.05). SEM micrographs were also showed that the chnges in the microstructur of the samples was different in the slow and frozen samples. Slow freezing methods had higher damge in the microstructure of the sample then quick freezing mathods. Sensory evaluation of the samples indicated that a better acceptability in the quick frozen samples than slow frozen sample (P<0.05).