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This study was carried out in 2016 to investigate the feeding on phytoplankton profile of the Nile tilapia (Oreochromis niloticus) and mango tilapia (Sarotherodon galilaeus) inhabiting Lake Nasser, and its relation to their fisheries biological parameters. Phytoplankton Preference index (PPI), Index of Relative Importance (IRI), and Straus Linear index were used to investigate the feeding patterns of the two species in the lake. Moreover, some fish biological parameters of the two species were determined in the lake different areas. The results showed that O. niloticus and S. galilaeus feed mainly on the same phytoplankton items. Bacillariophyceae was identified as the most desired phytoplankton item to O. niloticus (IRI = 12.53) and S. galilaeus (IRI=18.28). Both fish species were more selective to five species from Bacillariophyceae and five species from Chlorophyceae, while they were more avoidant to four species from Cyanophyceae at all lake's areas. The results also showed that the main fisheries biological parameters are varied significantly between the two species and through lake different areas. This study concluded that the variation in fisheries biological parameters in Lake Nasser is not related to the pattern of feeding on phytoplankton but is led by other factors (e.g. fishing practices).

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PIRULINA has drawn attention throughout the last decades. It is an essential source of valuable products, such as proteins, phycobilins, carotenoids, phenolics, and unsaturated fatty acids. These products had been used in medicine, pharmaceutical, and agriculture. In this study, the effect of different growth media on Spirulina platensis was studied after the cultivation at optimum growth conditions; continuous light intensity (60μmol photons m -2 s -1 ), temperature (25±3ºC), and pH (9.0 ± 0.2). The growth was estimated through 42 days by optical density (OD), cell counting (CC), and chlorophyll contents. The results showed that Kuhl's medium was the optimum for S. platensis with the highest results, i.e.: (OD), (CC) and Chlorophyll content increased 11.57 times, 19.55 times, and 22.66 times of the initial record, respectively. KNO 3 showed the best nitrogen source for S. platensis, where the different parameters of growth elevated to 3.56 times OD, 7.33 times CC, and 1.91 total chlorophyll more than their corresponding control.

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