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Coastal aquaculture is faced with extreme variation in water quality. The Deeba Triangle on Lake Manzala is the largest marine coastal aquaculture-producing area on the Egyptian Mediterranean. Samples from 16 ponds were taken during four seasons (2014-2015), to investigate the variation of 12 water quality parameters at that region. We tested the hypothesis that there is no spatial or temporal variation in water quality of the fish ponds. Fish ponds were statistically clustered into three groups (p = 0.0005) coincident with their geographical location. Hypersaline and transparent waters characterized the western ponds; higher dissolved oxygen and higher nutrients characterized the central region. These spatial differences were principally due to variations in salinity and nutrients of the water sources used for irrigation of the ponds and to differences in the aeration management styles. Strong seasonality was seen in water temperature (following air temperature), nutrients, and turbidity (following the seasonal cycles of various water sources from the Lake Manzala and the seasonality of the petrochemical plants effluents close to these ponds). We conclude that municipal effluents significantly affected, spatially and temporally, the quality of the irrigation water used for coastal aquaculture purposes, which consequently might affect fish yield.

The marine copepod species Oithona nana is considered as one of the most successfully mass cultured Cyclopoida species in marine hatcheries. This study investigated the effects of four feed diets (soybean, yeast, rice bran, and corn starch) on the population growth, growth rate, population composition, fecundity, and fatty acid composition of native isolated Cyclopoida copepod species O. nana. The experiment was continued for 15 days and the copepods were fed on one of the four diets with a concentration of 1 g 10−6 individual day−1. The results revealed that corn starch was found to be the most supportive diet for population growth and population growth rate. For nutritional value, copepods fed on rice bran were detected to have the highest content of MUFA, PUFA, and the lowest SFA and SFA/UFA ratio; more importantly, the rice bran diet was the only treatment that showed C20:5ω3. Moreover, copepods fed on rice bran showed the highest significant female fecundity, copepodite, and nauplii percent. Finally, the protocols described in the current study concluded that the dry feeds, especially corn starch, are very useful and applicable in hatcheries for maximizing the fecundity and density of Cyclopoida copepod species, O. nana.

Abstract:This study aims to evaluate the effect of different graded levels of local yeast (Saccharomyces cerevisiae) on the growth performance of Africancatfish, Clarias gariepinus. At the start of the experiment, a total number of 140 healthy fish were chosen. The fish were weighed and then divided into seven experimental groups of 10 fish per 70 -L aquarium. The water was replaced every day, but the fecal matters were siphoned out daily. Each aquarium was supplied with dechlorinated water and aerated continuously by an air compressor, so that oxygen levels were kept close to saturation. Dissolved oxygen, pH and total NH3-N were monitored in each aquarium during the experimental period. Dissolved oxygen levels were monitored close to air saturation (5.6mg/L) and pH was always on the alkaline side (7.9), while NH3-N not more than 0.097mg/L and temperature 25.5co as well as photoperiod12:12 Light: Dark). One control and six experimental diets duplicate (B2%, B1%, B0.5%, B0.2%, B0.1%&B0.05%) were arranged. Baker yeast (Saccharomyces Cerevisiae) was not included to the control group; however a (B2% at B0.05%) group was supplemented with baker yeast at 20.0, 10.0, 5.0, 2.0, 1.0and 0.5 g per kg diet respectively.The experimental diets were formulated to contain approximately 33.64 % crude protein. The feed was provided two times a day (10:00 am and 2:00 pm). All the experimental groups were fed the experimental diets at a rate of 3% of the live body weight of the fish. The experimental aquaria were inspected daily to remove food wastes and dead fish. The conclusion from the economic point of view the use of cheap local baker's yeast for African catfish increases their growth and production under farming conditions. The present study indicates that live baker's yeast positively enhance some hematological and physiological parameters as a results of the feed utilization, growth and production performance of African catfish. 176