Egyptian Journal of Aquatic Research最新文献

Increased demand for the production of sharks in the Arafura Sea can lead to the overfishing condition, which resulted in the depletion of fish stocks. Effective management measures are crucial to ensure the sustainability of shark fisheries. The objectives of this study were to investigate the stock status and to recommend some management strategies for shark fisheries in the Arafura Sea. Length frequency data and some life history parameters were used to perform a length-based stock assessment of Carcharhinus sealei in the Arafura Sea. C. sealei has an asymptotic length of 102.25 cm with a growth constant of 0.36 year⁻¹. C. sealei has been exploited heavily, which was indicated by the current fishing mortality (F_cur = 1.2 year⁻¹), which was much higher than its natural mortality (M = 0.29 year⁻¹) and the optimal fishing mortality (F_40%=0.49 year⁻¹). This study revealed that the high fishing pressure of sharks has resulted in the stock overfished condition for C. sealei in the Arafura Sea, with the current spawning potential ratio (SPR_cur = 0.23) less than the reference point 40% SPR. The low selectivity of drift gillnet (current Lc₅₀ = 66 cm) caused the low spawning stock biomass of C. sealei. The stock rebuilding strategy would be required to increase the spawning stock biomass of C. sealei. A minimum legal size of 77 cm, a marine protected area, and effort controls were some management strategies that can be adopted for the sustainability of shark fisheries in the Arafura Sea.

This study aims to investigate the spatial and seasonal impacts on the biochemical responses of two bioindicators: Tridacna squamosa and Echinometra mathaei which inhabit the Red Sea coast of Egypt. Samples were collected from three sites during the summer of 2019 and the winter of 2020. Total protein, MDA, and enzyme activity of pyruvate kinase (PK) and lactate dehydrogenase (LDH) were measured in the gonads of the collected samples. The results confirmed that environmental variables vary at both spatial and seasonal levels, where the two species exhibited different patterns of biochemical response to internal and external stresses. In addition, both studied species did not resort to anaerobic respiration as a defense mechanism. Therefore, this study confirms that the use of biomarkers in the field shall be regarded as a general warning of internal and external stress.

The principal purpose of the present trial is to inspect the complete supply of nutritional fish oil by substituting lipid springs in an applied feed for Thinlip grey-mullet, Liza ramada fingerlings. The impacts of four lipid sources (fish viscera oil (FVO), poultry viscera oil (PVO), tallow oil (TO), and plant oil (PO)) compared with fish oil (FO) as a basal diet on performance growth rates, feed-utilization, biochemical structure of the body, specific blood constraints, and fatty acid profile were evaluated in Thinlip grey mullet fingerlings. The substitution of FO by four substitute lipids shows a non-significant but notable influence on growth performance. On the other hand, feed utilization productivity was significant for fingerlings nourished by the PVO diet. Fingerlings nourished by the PO diet showed significantly lower contents of the total body lipid compared to fingerlings nourished by other diets. Flesh fatty acid structure reflected dietary fatty acids composition. Higher polyunsaturated fatty acids (PUFAs) were detected in fingerlings' flesh nourished by FO, while lower contents were dedicated in fingerlings' flesh nourished by PO. Although saturated fatty acid (SAF) contents in fingerlings' flesh nourished by diet TO were greater than other treatments, these results are beneficial in nutritional design to decrease feed prices without compromising Thinlip grey mullet fingerlings growth.

To improve the water quality of Lake Burullus, Delft3D FM hydrodynamic model was applied to simulate the flow and transport models in the Lake. Both the in situ field data and the Lake up-to-date geomorphology were used to get a clear-cut figure. Four different scenarios were applied. The most appropriate solution was obtained from the fourth scenario that suggested constructing a new channel at the northwestern corner of the Lake connecting it to the open Mediterranean Sea and clearing some existing islands and reeds to enhance the free movement of the water among the entire Lake, especially in the western basin.

Surface water and surface sediment samples were collected from Bitter Lakes from winter to autumn 2018 to evaluate the impact of land-based activities on the distribution of arsenic (As), selenium (Se), tin (Sn), and mercury (Hg). The metal concentrations were measured in 12 sampling sites along Bitter Lakes in the Suez Canal by the hydride system MH10 coupled with an atomic absorption spectrophotometer. The most industrialized regions in the lake showed elevated levels of metals in the water and sediments compared to other studied areas. As, Sn, and Hg showed the highest levels in water during winter (9.66, 1.03, and 0.25 µg/l, respectively), while Se recorded its highest values during summer (2.60 µg/L). Similarly, the highest total concentrations of the investigated elements in the sediments were 22400.00, 605.85, 40.91, and 446.55 ng/g, respectively.

Mangrove ecosystems support diverse macroalgal assemblages, which are primary producers. Community composition, percentage cover of macroalgae, and physicochemical parameters of seawater were studied at two mangrove areas in the Red Sea, Egypt, from November 2020 to October 2021. In addition, we sought to study changes in the relative densities of macroalgal species of the Red Sea in the two studied areas by using a comparison of our studying data (2020–2021) with previous studies carried out in the same locations in 1997–1998. In order to characterize the spatial variations in algal composition, three 20 m permanent line transects and three 1-m2 quadrates were established at each site. Throughout the duration of the study, the physicochemical parameters varied significantly (p < 0.05) among the seasons and were slightly different between the two sites. Twenty-four species of macroalgae were collected and identified from the studied sites. Approximately 29.2% of these algae (7 species) belong to the Chlorophyta, 45.8% (11 species) to the Ochrophyta (class: Phaeophyceae), and 25% (6 species) to the Rhodophyta. Phaeophyceae species had the highest diversity and richness values at both sites. Comparing the composition of the community during the years 2020–2021 and 1997–1998 yielded no statistically significant differences (p > 0.05). Mangrove trees support a high macroalgae cover, resistant to most environmental circumstances. The macroalgal assemblages' stability in the two studied areas over the two decades shows the health and quality of the Red Sea waters.

Bioaccumulation of heavy metals in mangrove crabs has been reported and most of them are toxic to animals and potential human carcinogens. Given that the land crab Cardisoma armatum Herklots, 1951 is more consumed by surrounding populations, this study aimed to quantify the levels of metals in its tissues and to assess the human health risks. Soft tissues were isolated in adult crabs and frozen then; samples were dried, crushed and handled following the standard procedures. Human health risks were evaluated using some indices. Heavy metal levels in each tissue were shown in decreasing order: Fe > Zn > Al > Cu > Cd > Pb. Cadmium, lead and copper metals were in upper levels in the hepatopancreas (0.35, 0.19 and 7.88 mg/kg) whereas iron, aluminium and zinc were higher in muscles (129.30, 15.96 and 82.83 mg/kg). Most EDI values were apparently below the PTDI and CRLim values signifying that the consumption of C. armatum remains safe for consumers although, a limit in intake frequency might be required for children. For all metals, THQ and HI values were below the standard value 1 indicating no health risks in consumers due to the intake of single or several metals. Also, the carcinogenic risks for Cd and Pb metals are considered to be negligible because they are lower than 10⁻⁶. Overall, regarding the results, consumption of C. armatum seems harmless for human health in the study area.

This paper aims to investigate the relationship between water quality variables and fish blood profiles in Arab al-Ulayqat Lakes in Abu Zaabal, Egypt, during the years 2021 and 2022. It also investigates how water pollution affects the quality of Nile tilapia (O. (Oreochromis) niloticus). Water quality parameters were measured, and concentrations of six metals—namely Cu²⁺, Cd²⁺, Fe²⁺, Ni²⁺, Pb²⁺, and Zn²⁺—in water and fish were determined. In addition, the hematological and biochemical parameters of fish were evaluated. Results revealed that the water in the three lakes was brackish and seriously polluted. Lake #3, in particular, was highly ammonia-concentrated and had organic contaminants and metal ions. The results showed high resistance of O. niloticus to water pollution and relatively low accumulation of pollutants in muscle tissue. O. niloticus from Lake #3 had considerable Cu²⁺ and Zn²⁺ contamination. The results of the fish examination revealed that changes in water quality variables have a significant impact on the blood profile of fish. Fish from Lake #3 showed increased levels of amino-aspartate activity transferase (AST) and alanine aminotransferase (ALT), which indicates hepatotoxicity. All fish from the lakes exhibited increased values of creatine and urea, which indicates nephrotoxicity and reduced antioxidant enzyme activity. The hazard index (HI) analysis demonstrated that heavy metals had no deleterious consequences for human health through the daily consumption of fish gathered from the Nile River, Lakes #1 and #2. However, the HI for Lake #3 showed that the investigated heavy metals adversely affected health.

Histological aberration is a common phenomenon in aquatic animals exposed to pollution. Pollution also influences the hormonal condition of an organism, including the green mussel Perna viridis. In the present study, degeneration and lyses were studied in the females' oocytes of P. viridis and the 17-β-Estradiol was measured in the gonads of female and male individuals. The damage analysis was carried out and the aberration level in the tissue was measured by image processing analysis using R-Software. The concentration of 17-β-Estradiol in the gonads was measured by the ELISA method. Histopathological aberration and 17-β-Estradiol concentration in the female gonad tissue of P. viridis were detected in the samples with variable quantities. The high value of 17-β-Estradiol in males cultured in the industrial city of Indonesia indicated that this mussel species experienced hormonal imbalances and represent a threat with regard to food safety.

Heavy metals entering seawater pose a global threat to marine life and the ecological system. In this regard, this study investigates the mass balance of copper in Abu Qir Bay, a shallow basin located in the western Mediterranean coastal zone of Egypt. The study area is well-thought-out as a fertile marine habitat, which emphasizes the presence of naturogenic and anthropogenic activities. Three land-based sources, namely al-Tabia outfall, al-Maadia outlet, and the Rosetta branch of the Nile River, are seriously affecting the bay causing pollution problems. As part of this research, rainfall, seawater, and drainage water samples were collected to determine and evaluate the relative importance of different sources on the geochemical cycle of copper in the bay. The results revealed that the mean total concentration of copper in the bay was 74.61 ± 18.37 μg/l. Abu Qir Bay receives about 1374.8 ± 171.05 and 643.13 ± 153.03 tons of copper annually from agricultural and industrial discharges, respectively. The outflowing surface water from the bay transports 2463 ton/year of the total amount of copper to the southeastern Mediterranean water. The calculated residence time of copper in Abu Qir Bay was 101 days, while the assimilative factor of copper in the bay amounted to 40 ton.m³/mg.year. As per the findings, a 90 % reduction of the total copper concentration in the bay, in case the external loading stops, can act as an important solution for quick recovery of the bay condition to reach 7.5 μg/l after 121 days.