The present study was designed to evaluate the use of Spirulina, Arthrospir platensis as a protein source for hybrid red tilapia fries (Oreochromis niloticus x Oreochromis mossambicus) with average weights of 206±11 mg. Spirulina was incorporated into diets at 0, 50, 75, and 100% of the fishmeal-based diet. The test diets were fed to the fish at 12% body weight three times a day for consecutive 65 days at 24±2°C. The final weight gain, specific growth rate, feed conversion ratio (FCR) and survival rate of fish were evaluated. The present study suggests that up to 75% of Spirulina can be substituted for fishmeal in a fishmeal-based diet for hybrid red tilapia with increased feed conversion ratio and protein productive value in carcass proximate composition. Also higher immunity can be observed than other treatments, where white blood cells were 4.08 x10 3 mm. In conclusion, the results of this study indicate the possibility of using Arthrospira platensis as commercial nutrient source for large scale culture of fish in general and tilapia in particular.

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Despite macroalgae epiphytes play an important role in algal habitats, available information from Alexandria coastal waters is scarce. To evaluate the role of environmental factors on the inventory of the ephyphytic Ostreopsis c.f ovata cells, its abundance on the thalli of 14 different macroalgae collected from two sites at Abou Qir rocky area was done on the basis of sampling carried out for one year. The annual maximum Ostreopsis cf. ovata cell abundance was observed in May (late-spring), reaching the maximum on the green macroalgae Ulva linza in July (mid-summer). Analysis of variance showed significant difference of abundance between seasons and hosts. Water temperature and NO 2 , NO 3 and PO 4 seem the major factor affecting on abundance of Ostreopsis c.f ovata. The present study documented the significant importance of Ulva sp. as the suitable host of O. ovata in Alexandria waters, in contrasting with others in the Mediterranean Sea that show O. ovata most often found on Phaeophyta and Rhodophyta.

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Based on weekly sampling, the present short-term study was set out over a one-year cycle in the Eastern Harbor (Alexandria, Egypt). This study aims to assess water quality monitoring data. Among the 13 indexes used in the present study to define the water quality in the harbor, 6 depend on physical and chemical variables, and the other 6 are biological criteria. Chlorophyll concentrations and phytoplankton cell numbers were also used as indicators for assessing trophic status. The study indicated that water status mesotrophic and poor-bad classes are the major trend in the harbor, but oligotrophic condition dominates in winter, and the eutrophic status and poor class dominate in autumn. Looking for suitable tools to assess the water status in such a highly dynamic marine basin is not a simple task, and identification of a common quality status relying on a single assessment approach is hard to realize. Despite the consensus between some approaches, significant discrepancies were observed in the classification results on temporal scale, and for the inability of some indices to sort all types of water bodies in the harbor. The study might represent an integral part of holistic ecosystem-based management of coastal waters.