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The present study deals with the effect of four commercially prepared diets on the length-weight relationship, condition factors, growth performance and feed utilization of the cichlid fish, Oreochromis niloticus fingerling reared in glass aquaria. The major components of diets included proteins, fats and carbohydrates of each feed type. The diets were analyzed for verification of values written on its commercial label. Data showed that, the standard length of the fish fed on the different diets did not vary significantly where it ranges between 6.28 ± 0.9 cm in diet II to 6.66 ± 0.8 cm in diet I. The same pattern of change was also noticed in comparing the weight of fishes fed on the four diets. Data indicated that, fish feeding on diet IV demonstrate the lowest weight being on the average of 8.86 ± 1.97 gm, while, fish feeding on diet I showed the highest weight being averaged 10.37 ± 3.2 gm. The growth of fish is nearly isometric in the first three diets and negative allometric in the fourth one. The values of condition factors are slightly differences among different diets. The highest value (3.46) of coefficient of condition (k) was recorded in the fish fed on diet II and the lowest value (3.09) in the fish fed on diet III. The highest average value (1.07) of the relative condition factor (kn) and the lowest (0.90) were recorded in the fish fed on diet III. The lowest value of total weight gain, average daily gain and specific growth rate were detected in the fish fed on diet IV. The value of feed intake of diet I is better than the values obtained from the other feed diets. The best feed conversion ratio (1.87) was recorded in the fish fed on diet II. The lower protein efficiency ratio (0.25) was recorded with diet IV and the higher protein efficiency ratio (0.53) was recorded with diet II.

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Gastropod shells can be a limiting factor in allowing hermit crab populations to increase. The impact of this factor on population size of the land crab Coenobita scaevola (Forskäl, 1775) was examined. Extensive and intensive works were conducted on a sandy beach of Wadi El-Gemal island and the protected area coast (35°04'0"E, 24°42'0"N). Activity, spatial and temporal distribution, food foraging, and impact of human tourism activities for this hermit crab were discussed. A total of 365 crab individuals were collected from the sandy beach of Wadi El-Gemal island during August 2007 to July 2008, among these 137 were used for frequency measurements of occupied shells by the land hermit crabs. The hermit crabs were found occupying seventeen species of gastropod shells. A significant regression and correlation were recorded between the shell aperture and chelae. However, our data showing no significant regression values between total body weight of crabs and for each of the shell weight and internal volume. From the other angle, the correlation relationship recorded high significant value for the same relationships. This may reflect that some smaller crabs tend to occupy larger shells than the preferred ones. Moreover, the shell species occupation as a function of chelar hermit crabs size. While the negative results between body weight of crab and both shell internal volume and weight it may be due to the variations behavior of some land hermit crab individuals within population. It is logical that fit the size of chelae with aperture of shell to achieve protection from predators while some members of the population that occupied shell is greater than the size of his body to the unavailability of appropriate shells.