Egyptian Journal of Aquatic Research最新文献

This study investigates groundwater resources in the El-Omayed area on the northwestern coast of Egypt. The aim is to assess the extent and severity of saltwater intrusion in the shallow aquifer system, as well as its potential impacts on groundwater resources. A combined geophysical and hydrochemical approach was adopted in this investigation. Across the study area, 32 vertical electrical soundings were conducted, along with two electrical resistivity tomography profiles. Sixteen water samples were collected, and then chemically analyzed to evaluate water quality, seawater intrusion, and source of salinity. The results of geophysical interpretation revealed the existence of a thin, shallow freshwater-bearing layer (42–95 Ω.m), predominantly situated in the central parts of the area, followed by saltwater saturated layers of (0.9–2.1 Ω.m) affected by the Mediterranean Sea invasion. The eastern portion of the aquifer also recorded a relatively high seawater intrusion. As evidenced by the actual data gathered from drilled wells, the study area can be divided into three distinct zones: fresh, brackish, and saltwater zones. The study identified the most suitable sites to establish new groundwater wells, in addition to identifying the source of salinity through the investigation of the geochemical properties of water samples.

In the marine environment, polycyclic aromatic hydrocarbons (PAHs) constitute one of the most pervasive and harmful types of organic pollutants. They pose an additional hazard to marine creatures' resilience due to ongoing climatic change. Therefore, determining their concentration and source is important for estimating their possible risks. Utilizing (GC–MS), we analyzed PAH levels in marine algal tissues along the Red Sea's Ras Gharib coastline. The present study covered the collection of seven Red Sea macroalgae namely; Sargassum cinereum, Caulerpa racemosa, Ulva intestinalis Linnaeus, 1753, Turbinaria ornata, Hormophysa cuneiformis, Ulva lactuca, and Cystoseira myrica) from the Ras Gharib coastline. Sixteen PAHs were found at quantities ranging from 159.67 to 261.57 ng/g in all of the examined marine algal tissues. The average concentration of the 16 PAHs was the highest in S. cinereum and the lowest in U. lactuca. The mean concentration of benzo(a)anthracene (BaA) in S. cinereum was 74.12 parts per billion (ng g⁻¹). Two- and three-ringed PAHs with a lower molecular weight amounted to 2.51 to 23.54% of all PAH components in algal tissues. The average contribution of the eight cancer-causing PAHs to the total TEQcarc of the investigated species was sequentially as follows: BaP (50.23%), BaA (32.18%), BbF (6.52%), BkF (5.20%), IP (4.50%), and Chr (2.00%). The results of the diagnostic ratios demonstrated that the primary causes of most PAHs were combined pyrogenic and petrogenic activities. This suggests employing these indicators to investigate the biological impacts of PAHs pollution and establish its bioavailability in the marine environment.

Given the cruciality of the thawing process to fish and their products as well as its impact on fish quality, this study aims to assess how different thawing techniques affect bacteriological changes, microstructure, and antioxidant activity enzymes in frozen fish fillets. As revealed, microwave thawing (MT) is a quick method, showing low microbial count and the least activity of antioxidant enzymes, while flowing water thawing (WT) preserves the fish microstructure.

Zinc oxide nanoparticles (ZnO NPs) pose a major threat to aquatic life and their presence in the aquatic environment requires attention. This study intends to examine the impacts of ZnO NPs on Brachidontes pharaonis. Brachidontes pharaonis were divided into four groups, the control group and experimental groups exposed to ZnO NPs at concentrations of 1 mg/L, 5 mg/L, and 8 mg/L. The results revealed a decrease in protein and glucose, along with an increase in cholesterol, HDL, LDL, and triglycerides. The SDS-PAGE showed changes in the concentration of protein. In histological observations, there was necrosis in the epithelial cells, infiltration in the connective tissue between ovarian follicles, hemorrhage of blood vessels in gill filaments, and fibrosis in muscle myofibrils. Histochemical studies showed a rise in mucous cells in gill filaments and an increase in collagen fibers in the muscle. As concluded, ZnO NPs lead to alteration in biochemical parameters, protein profile, and histopathological changes in B. pharaonis.

Zinc oxide nanoparticles (ZnONP) are increasingly utilized in many products worldwide. Eventual release into the aquatic system poses various environmental hazards and raises concerns for aquatic life and public health. In the present study, the effects of waterborne ZnONP and dissolved Zn⁺² (ZnSO₄ 7H₂O) were investigated in Siganus rivulatus through experimental exposure to environmentally relevant concentrations (40, 200, and 400 µg/L) of Zn in both forms. Fish exposed to ZnONP exhibited a higher accumulation of zinc in their muscles, whereas exposure to Zn⁺² ions led to elevated zinc levels in the gills and liver. The physiological and histopathological analyses revealed distinct responses between the two experimental groups. ZnONP exposure stimulated the antioxidant system, resulting in a significant elevation (1.7–2 folds) of superoxide dismutase (SOD) and catalase (CAT) enzymes in the gills. On the other hand, Zn⁺² ions increased the levels of SOD, CAT, and Glutathione-S-transferase (GST) enzymes 1.5–2.4 times in the liver, along with 1.9–2 folds higher lipid peroxidation (LPO) in both the liver and gills. Histological examination of the gills revealed lamellar fusions, degenerative alterations, and infiltration of melanomacrophagic centers, indicating the impact of both treatments. Similarly, the liver tissue showed cytoplasmic vacuolation and significant infiltration of melanomacrophagic centers engorged with brown spots. These histopathological changes were more severe in fish exposed to all concentrations of Zn⁺² and in fish exposed to 400 µg/L of ZnONP. This study concludes that waterborne Zn⁺² exhibited higher toxicity in fish liver and gills compared to ZnONP. However, the mechanisms of ZnONP uptake by fish tissues remain unclear and require further investigation.

The determination of the maritime boundary is related to the selection of the tidal datum used in relation to the zero-depth reference. This research was conducted to determine the impact of the zero-depth reference that has been used, the Mean Low Water Spring (MLWS), against the zero-depth recommended by the International Hydrographic Organization (IHO), the Lowest Astronomical Tide (LAT). Tidal data is obtained from BIG's tidal station processing, while the MLWS value data is obtained from a combination of analysis from the Hydrographic Office of Indonesia (Pushidros). Based on these data, it is found that 25 out of 37 tidal stations indicate that the LAT value is below the MLWS in its vertical position. This shows that sea boundary claims can potentially be shifted by changing the zero-depth reference from the original by switching from MLWS to LAT. Lastly, this study presents the benefits of implementing the vertical system reference recommended by the IHO, the LAT, as an international chart datum.

This present study first estimated the length and weight relationships of six freshwater endemic and endangered fish species collected from the main channel of the Yangtze River in China. The samples were captured quarterly from 13 different channel segments of the Yangtze River between October 2020 and August 2021. The total length and body weight were estimated for each sample. The a and b parameters of the length and weight relationships were calculated from log-transformed equation with 95 % confidence intervals. Correlation coefficients showed a high degree of positive correlation between the length and weight for five species, Pseudobagrus tenuifurcatus, Ancherythroculter nigrocauda, Chanodichthys oxycephalus, Culter oxycephaloides, and Saurogobio dumerili (r² > 0.91), and slightly lower positive correlation for an endemic species Acipenser dabryanus Duméril, 1869 (r² = 0.84 at p < 0.001). Our results have added new data on the length and weight relationships of the six freshwater species, and renewed the maximum length for the FishBase database.

The objective of the current study was to describe the female reproductive characteristics of populations of the non-indigenous shrimp Penaeus latisulcatus off the Egyptian Mediterranean coast. P. latisulcatus was sampled from the commercial catch of Boughaz El-Maadiyah's landing center off the Mediterranean coast between July 2020 and June 2021. This study focused on describing maturity stages, calculating the gonadosomatic index (GSI), determining the spawning season, and measuring the size at first maturity of female P. latisulcatus. The stages of ovarian development were divided into six stages; i.e., immature, early maturing, late maturing, nearly ripe, ripe, and spent. A prolonged spawning season was identified, extending from the summer season to autumn and showing a peak in August. The GSI followed the same pattern of ovarian maturation and confirmed the spawning season of P. latisulcatus. As revealed, 50% of female individuals attained maturity at a total length of 11.34 cm. Hence, this study provides fundamental and helpful information for understanding the reproductive dynamics of P. latisulcatus on the Egyptian Mediterranean coast as a new habitat for its propagation. This information also helps in providing the proper management of fisheries and conservation of this shrimp species, which can be useful for aquaculture processes as well.

The introduction of the crayfish Cherax quadricarinatus into new areas of Malaysia resulted in the introduction of new parasites that harmed other aquatic organisms. A study was conducted to determine the prevalence and sites specificity of temnocephalids in wild and cultured Cherax quadricarinatus. In this study, 33 wild (Melaka) and 32 cultured (Johor) C. quadricarinatus were sampled in January 2020. The prevalence of the parasite was determined using dissecting microscopes and their sites specificity were compared. The prevalence (P) and mean intensity (MI) of temnocephalids in wild crayfish were 93.94% and 35.13%, whereas in the cultured crayfish were 100% and 18.31%, respectively. The temnocephalid species were identified as Diceratocephala sp., Craspedella sp., and Decadidymus sp. The prevalence of adults and eggs of Decadidymus sp. was found to be significant in cultured C. quadricarinatus (p < 0.05). Significant differences were observed by adult Diceratocephala sp. and Craspedella sp. on the cephalothorax and walking legs, and in the gills and gill covers of wild C. quadricarinatus, respectively. These findings showed that the cultured C. quadricarinatus had a higher temnocephalid infestation compared to the wild C. quadricarinatus. These different temnocephalid species occupied different niche areas, but factors accounting for their distribution on C. quadricarinatus need further investigation.

Four sustainable feeds were formulated with locally available ingredients of Benin, produced by extrusion, chemically and physically characterized and their performance was explored. Formulated feeds (F1, F2, F3 and F4) and a Control Feed (CF) were fed to Clarias gariepinus juveniles for 16 weeks and fish growth parameters were monitored. Nutritional and sensorial qualities of the fresh and smoked fish were evaluated. Formulated feeds had the same levels of protein and carbohydrate contents and were similar to CF in this concern. The fat content of F2, F3 and F4 feeds was lower than that of the CF except for F1, which had similar fat content. All tested feeds had floatability rates exceeding 80%. The mean weight gain of the fish ranged from 168 g to 401 g. The best Feed Conversion Ratio was recorded with CF (1.01) followed by F2 (1.21). The Protein Efficiency Ratio of F2 (2.14) and CF (2.51) did not differ statistically. Fish fed with F2 had the best nutritional profile (protein: 682 g/kg, and fat: 231 g/kg) compared with fish fed on other feed formulas and the CF (protein: 634 g/kg, and fat: 274 g/kg). Smoked fish fed F2 and CF recorded similar acceptability from consumers.