Fishmeal is the most expensive feedstuff in the aquafeed and one of the most environmentally limiting factor of aquaculture development. Therefore, the search for alternative protein sources is a continuous process. The present feeding trial was conducted to evaluate the effects of replacing fishmeal with zooplankton biomass meal (ZBM) on the growth performance, nutrient utilization, intestine, and liver histological changes of grey mullet, Mugil cephalus (initial weight of 0.10 ± 0.01 g). Five isoproteic (35% crude protein) and isolipidic (8% crude lipid) diets were formulated as the control diet (Z₀) and the other four diets (Z₂₅, Z₅₀, Z₇₅, and Z₁₀₀), where 25%, 50%, 75%, and 100% of fishmeal was replaced by ZBM, respectively. After 60 days of feeding, the final weight, weight gain, and daily growth index of the grey mullet fed the Z₁₀₀ diet were higher than those fed the control diet (p < 0.05). In addition, the better values of feed conversion ratio, protein efficiency ratio and lipid efficiency ratio were recorded in the fish fed with the Z₁₀₀ diet. Additionally, the intestinal villus length, crypts depth, and muscle thickness were significantly improved with ZBM inclusion (p < 0.05). Meanwhile, there were no histopathological changes observed on the liver when compared with the control group. From the economic point of view, dietary substitution of fishmeal by ZBM (Z₁₀₀) reduced the cost of diet formulation by 18% and the price per kg weight gain by about 40%. Overall, according to the findings of this study, substituting fishmeal with ZBM up to 100% could improve growth performance, feed utilization, gut health status, and profit ability of rearing M. cephalus juveniles.

The present study aimed to describe the dorsal fin measurements used to differentiate between some shark species in Egyptian Mediterranean waters. A total of 43 specimens of sharks were seasonally collected from the commercial catch of the Mediterranean Sea land fish markets in Alexandria, during the period from May 2017 to June 2018. Morphometric characters of dorsal fin were recorded for each specimen. Many photos had been captured for each shark specimen to be processed by Image J software to calculate different ratios of morphological aspects for dorsal fin. Results showed that the collected specimens belong to 8 species (Heptranchias perlo, Hexanchus griseus, Squalus megalops, Centrophorus uyato, Oxynotus centrina, Squatina squatina, Isurus oxyrinchus and Isurus paucus) and three species of them (Heptranchias perlo, Squalus megalops and Isurus paucus) are a new record in the Egyptian Mediterranean waters. The morphological aspects of dorsal fin in these eight shark species were greatly varied in shape. The morphological aspects of studied shark species proved the potential capability of this method for shark species identification. The statistical analysis of morphometric ratios showed significant variances between investigated species. Our study attempted to add more update information on shark dorsal fin morphological and dimensional scaling.

The present study aimed to compare between gill rakers of some marine fishes with different feeding habits. A total of 78 specimens in 13 species belonged to 6 fish families: Sparidae (Sparus aurata, Diplodus noct, Rhapdosargus haffara and Boops boops); Family: Mugilidae (Mugil cephalus, Mugil capito and Liza aurata); Family: Siganidae (Siganus rivulatus and Siganus luridus); Family: Synodontidae (Saurida undosquamis and Synodus saurus); Family: Clupeidae (Herklotsichthys quadrimaculatus) and Family: Carangidae (Caranx sexfasciatus) were collected by irregular visits from land fish market in different localities of Egyptian Mediterranean Sea and Suez Gulf; during the period from March, 2014 to November, 2014. Results showed that, the first gill arch formed of one piece, consisting of two limbs (upper and lower limbs). The gill arch carried two rows of gill rakers on its concave border and two rows of gill filaments on its convex one. The gill rakers in the anterior row (oral row) are longer, more in number and more developed than that of the posterior row (aboral row). The gill arch in family Sparidae is bow-like shape. The anterior gill rakers on the first gill arch of most sparid species are short, conical in shape adapted to carnivorous feeding. The gill arch of fish species in Mugilidae is mostly crescent-shaped and rarely bow-shaped. The anterior gill rakers on the first gill arch are long and great in number adapted to detritus feeding. The gill arch in family Synodontidae is V shaped. The anterior gill rakers on the first gill arch appeared as clusters of small tooth patches adapted to piscivores feeding. The gill arch in family Siganidae is hook-like shape. The anterior gill rakers on the first gill arch were needle spine in shape with secondary projections adapted to herbivorous feeding. The gill arch in fish species of Clupeidae is V like shape. Gill rakers are well developed and arranged in only one row. They are numerous and elongated adapted to seizing food items in the plankton feeding. The gill arch in fish species of Carangidae is bow-like shape. Gill rakers are moderate in length and number adapted to carnivorous feeding. According to the different feeding habits, the results showed that, the highest average length of the first gill arch (mm) is recorded in carnivore and piscivore fish. The maximum averages number and the length of the anterior gill rakers are recorded in detritivore fish and plankitivore fish. The highest percentages of the anterior gill raker length /gill arch length ratio (%) are recorded in plankitivore fish and detritivore fish. Results showed that, the maximum inter raker space (µm) and the inter raker space/gill arch length (%) is recorded in carnivore fish. The maximum breadth at the raker base (µm) in the anterior row of rakers is recorded in piscivore fish. The highest breadth at the raker base/gill arch length (%) in the anterior row of rakers is recorded in carnivore, piscivore and planktivore fish. The highest posterior gill raker length (µm) and the posterior gill raker length /gill arch length ratio (%) are recorded in detritivore fish. In conclusion: The morphological characters of the gill rakers in the first gill arch were differ in species studied according to different feeding habits. So that, can be used in determine the fish family and feeding habits.

The present study aimed to analyze the effect of stocking densities and feeding rates on growth performance and fish production of O. niloticus reared in earthen ponds. This experiment was conducted for 7 months extended from May to November, 2016 in 12 earthen ponds at Parsik Culture, Idko, Behira Governorate, Egypt. Each pond has 2 feddan with an average depth of 1.0 m. Monosex fries of Oreochromis niloticus were divided into 4 treatments {T1: stocking density of 6 fish/m3 with a feeding rate of 2.5%; T2: 6 fish/m3 with a feeding rate of 3.5%; T3: 8 fish/ m3 with a feeding rate of 2.5% and T4: 8 fish/ m3 with a feeding rate of 3.5%}, each treatment had 3 replicates. Results showed that the highest values of growth performance (growth in length, length gain, daily length gain, growth in weight, total weight gain, daily weight gain and specific growth rate) of O. niloticus were recorded in T3(high stocking density and low feeding rate). On the other hand, the lowest values of these parameters were recorded in T1 (low stocking rate with low feeding rate). The best average of food conversion ratio (1.37± 0.025) was recorded in T3 and its a bad average (1.56±0.034) was recorded in T2. Also, the highest average values of protein efficiency, feed efficiency ratio was recorded in T3, and their lowest values were recorded in T2. The maximum total costs were calculated for T4 and its minimum values were calculated for T1. But, the maximum net income value was obtained from T3 and the minimum net income value was obtained from T1. Conclusion: The growth performance, the best food conversion ratio, protein efficiency ratio and feed efficiency ratio of O. niloticus reared in earthen ponds was positively correlated with high stocking density (8 fish/ m3) and not correlated with feeding rates (2.5 or 3.5%). The net income of O. niloticus cultured in earthen ponds was positively correlated with high stocking density and low feeding rate (8 fish/ m3 with a feeding rate of 2.5%).

The present study aimed to provide an update on carcharhinid sharks (Family: Carcharhinidae) in the Egyptian Mediterranean waters, based on the differences in morphological features of the body. A total of 36 specimens of carcharhinid sharks belong to 7 species of family Carcharhinidae were seasonally collected from the commercial catch at land fish market in Alexandria of Mediterranean Sea, during the period from May 2017 to June 2018. Morphometric characters were recorded for each specimen. Many photos had been captured for each shark specimen and processed by Image J software for calculating different ratios of morphological aspects for shark’s body. Results showed that seven species belonging to the family Carcharhinidae (Carcharhinus altimus, C. brachyurus, C. brevipinna, C. falciformis, C. obscurus, C. plumbeus and Prionace glauca) were found to inhibit the Egyptian Mediterranean waters at Alexandria. Four of them were firstly recorded in the Egyptian Mediterranean waters (i.e. C. brachyurus, C. falciformis, C. obscurus and Prionace glauca. Our study was attempted to add some morphometric characters for the identification of studied species. Statistical analysis of morphometric ratios showed significant differences between investigated species (P<0.05), revealing its capability as classifying tool.