Egyptian Journal of Aquatic Research最新文献

Lake Manzala, the largest Egyptian coastal lake, is one of the most valuable fish sources in Egypt, which contributes about 14% to the total annual Egyptian fisheries production. However, given that Lake Manzala suffers from major environmental and fisheries problems, an ambitious national project for the dredging, purification, and development of this lake was established in 2017. Hence, this study was conducted to assess seasonal diversity and to provide an inventory of fish species at Lake Manzala during dredging operations. Five seasonal surveys were conducted during the period from 2019 to 2021. By using different fishing gears and methods operating in the lake, a total of 7774 fish and crustaceans—belonging to 29 fish species and three crustacean species that clump into 21 families—were collected from Lake Manzala. During the study period, the family Cichlidae showed the highest occurrence of about 70%. The marine-brackish species recorded the highest aquatic environment (milieu) diversity with 34.4% of the collected species, but only 12.5% of the freshwater species. Six of the collected fish species were recorded of Indo-pacific origin, as Lissepsian migrant species. In this study, the diversity index (H) was calculated, ranging between 1.13 and 1.77. As indicated by the seasonal variation of the diversity index, the highest diversity index of Lake Manzala was evident in autumn 2019 and spring 2021 at 1.700 and 1.365, respectively. The governmental dredging and cleaning operations in the lake have a relative impact on the species composition in this area. Further studies are recommended after the completion of these operations to confirm the impact of dredging on species composition alteration.

This study aims to discuss some physicochemical parameters and their effect on steel corrosion rate in natural seawater collected from different sectors along the Egyptian coast of the Mediterranean Sea. Samples were collected from eight eastern sectors including 48 stations during autumn of 2021, and from twelve western sectors including 72 stations during spring of 2022. The steel corrosion rate was determined by using the weight loss technique on a laboratory scale. Results ranges and total averages revealed that salinity (20.630–42.020) 38.540‰ in 2021 and (37.771–39.304) 38.831‰ in 2022; the pH (8.28–8.41) in 2021 and (7.69–8.15) in 2022; dissolved oxygen (3.00–4.73) 3.65 mg/L in 2021 and (2.88–6.98) 4.481 mg/L in 2022; oxidizable organic matter (1.10–2.60) 2.08 mg/L in 2021 and (depletion–0.93) 0.304 mg/L in 2022; phosphate (0.022–10.876) 4.142 µM in 2021 and (depletion–5.432) 0.612 µM in 2022; nitrite (depletion–1.325) 0.379 µM in 2021 and (depletion–2.50) 0.211 µM in 2022; sulphate (2.044–3.876) 2.997 g/L in 2021 and (1.544–4.425) 2.645 g/L in 2022; and the steel corrosion rate (0.020–0.158) 0.088 mm/y in 2021 and (0.006–0.197) 0.078 mm/y in 2022. According to the Principal Component Analysis (PCA) data, the western stations had good water quality, while the eastern stations were polluted in different degrees related to the increase in human activities. Two statistical equations were obtained from the correlation between the steel corrosion rate and their corresponding physicochemical parameters.

Heavy metal contamination caused by human activities is a major threat to aquatic organisms. Therefore, a 28-day trial was designed to evaluate the hematological and histological changes in Labeo rohita exposed to chromium chloride. For this purpose, 240 fish (Labeo rohita) were randomly selected and divided into four groups. Three groups were treated with a sublethal waterborne concentration of chromium (37, 22, and 11 mgL⁻¹); the fourth group was chromium-free control (0 mgL⁻¹). Results demonstrated that noted values of hematological parameters, such as mean cell hemoglobin, red blood cells, hematocrit, platelets, and hemoglobin, were decreased significantly (P < 0.05) in experimental groups compared with control, while mean cell volume and white blood cells were increased. On the 28th day, a decline was observed in white blood cell values. The severity of histological lesions in the liver, kidney, and gills increased as the concentration and duration of chromium exposure increased. No histological change was observed in the control (T₀), while T₁ showed more severe changes than T₂ and T₃. Those results suggest that long-term exposure to chromium chloride causes adverse effects on the hematology and histology of major carp, Labeo rohita.

The growth and population parameters of spotted seabass (Dicentrarchus punctatus) in Bardawil Lagoon were investigated to assess their fishery status and propose concrete recommendations for sustainable exploitation. The samples (n = 271) were collected from commercial catches during 2021. As revealed by examining the otoliths, D. punctatus has a short life span of a maximum of four years based on the mean lengths of 20.2, 25.3, 29.7, and 33.5 cm for age groups from I to IV, respectively. The total length-weight relationship equations were W = 0.0120TL^2.9672 for males, W = 0.0127TL^2.9486 for females and W = 0.0124TL^2.9563 for the combined sexes. The von Bertalanffy growth function was L_t = 40.50(1-e^{-0.38(t+0.66)}). The study determined the total and natural mortality rates as 1.58 and 0.79 year⁻¹, respectively, with an exploitation rate (E) of 0.49, which was found close to the optimum value (0.5). However, based on management policies, E was greater than the value corresponding to 50% relative biomass per recruit (E_0.5), which indicates that the current fishing effort is unsustainable. Therefore, to maintain the biomass of spawning stocks, the study recommends a 22.4% reduction in the current exploitation rate through the application of fishing regulations that decrease fishing efforts. Such recommendations can help ensure the sustainable exploitation of spotted seabass in Bardawil Lagoon.

This study aimed to determine the effect of hauling and soaking time of stationary lift nets on the pattern of fish aggregation in the Banyuasin waters, South Sumatra, Indonesia using a hydroacoustic monitoring approach. The fish aggregations were monitored using the SIMRAD EK-15 single beam (200 kHz) during hauling, and the transducer was mounted on the side of the fishing gear. Furthermore, data were collected before (17:00–23:59) and after midnight (24:00–05:00) at four different soaking times (S₁, S₂, S₃, and S₄). The data obtained were then analyzed using pairwise comparisons (nonparametric tests). The pairwise test (p = 0.25 > 0.05) showed that there was no significant difference between the acoustic mean densities obtained before and after midnight (292.2 and 178.9 g/m³), but the total values for both periods varied widely (6,797 and 3,507 g/m³). Dunn’s post hoc tests (p = 0.001 < 0.05) revealed that there were significant differences in the acoustic mean densities between S₁ (1–16 min) and S₂ (17–32 min). Based on the results, the optimum soaking time was 17–32 min, which was recommended for improving the effectiveness of the stationary lift nets. Furthermore, fish aggregation began to spread out of the catchable area when the soaking time was over 32 min.

This study aims to elucidate the carrying capacity of estuarine mangroves in Southeast Sulawesi, to maintain environmental health of its coastal cities. The concentrations of mercury (Hg), Copper (Cu), Manganese (Mn), Lead (Pb), Zinc (Zn), and Nickel (Ni) were analyzed in sediments and mangrove tissues samples from Kendari bay and Tinanggea estuaries. This was followed by the determination of translocation and bioaccumulation factors, as well as the total accumulation of heavy metals on a landscape level. The results showed that the sediment in Kendari Bay had higher heavy metal concentrations than in Tinanggea, indicating the anthropogenic impact of the highly populated city of Kendari. Moreover, the roots and stems of mangroves had higher heavy metal concentrations than the leaves. Overall, the Bioconcentration Factors (BCF) of Hg, Cu, Mn, Pb and Zn metals were >1, indicating that estuarine mangroves have a higher phytoremediation capacity for heavy metals. Estuarine mangrove biomass also enables the high accumulation of heavy metals in both Kendari bay and Tinanggea, signifying the greater phytoremediation potential of urban estuarine mangroves. Based on these findings, the study supports the conservation and management of mangroves in urban estuaries to maintain the environmental health of coastal cities.

Blood clam or blood cockle (Anadara granosa) is a clam species with high calcium carbonate (CaCO₃) and chitin content; these compounds are commonly used in coagulation water treatment. This study examined the capacity of blood cockle shells (BCS) as an innovative natural coagulant in the form of unmodified powder (BCSP) and chitosan extracted from the shells (BCSC) to reduce TSS and turbidity of well-water. SEM and FTIR analysis were conducted to analyse the characteristics of the media. The coagulant dose, pH of the water sample, and settling time were investigated using a jar test experiment to determine the optimum condition for each experimental system. Rapid mixing (1 min at 120 rpm) was followed by slow mixing (10 min at 60 rpm), followed by settling times ranging from 10 to 30 min. The optimum settling time was 30 min, after which 76% TSS and 76% turbidity were removed using 75 mg/l of BCSP at pH 4. The tests with BCSC resulted in 80% TSS and 81% turbidity removal with 200 mg/l of BCSC at pH 5 and a settling time of 30 min. The results were compared to the performance of alum (Al₂(SO₄)₃·18H₂O), a commercial chemical coagulant. Under similar dosage (200 mg/L) and pH (= 6) conditions, alum reduced turbidity and TSS by 95% and 97%, respectively. These results indicate that blood cockle shell-based coagulant is a promising environmental-friendly material that can compete and possibly replace conventional chemical coagulants in water treatment systems.

This study aims to investigate the gonadal growth and gonads qualitative color assessment of the sea urchin Paracentrotus lividus in the Southeastern (SE) Mediterranean coast off Egypt. A total of 1895 sea urchins were collected between 2017 and 2018, and their reproductive biology parameters were determined. The gonadosomatic index with the histological analysis revealed that P. lividus has two spawning seasons (spring – autumn). Females and males have four maturity stages; recovery, growing, mature, and spent. Mature oocytes and sperms were observed during autumn, winter, and spring, while nutritive phagocytes dominated the tissue of both ovaries and testes in the summer season. The sex ratio (F: M) was male-biased (1: 1.2). The smallest observed size of mature males was 19.10 mm TD (test diameter), whereas the calculated L₅₀ was 26.2 mm. In females, the smallest observed size of a mature individual was 22.70 mm TD, and the calculated L₅₀ was 33.5 mm TD. The qualitative color assessment of the gonads revealed the dominance of excellent and acceptable color throughout the year (83.93%), with maximum value during the resting and recovery periods, while, the occurrence of unacceptable color was linked to the maturation and spawning periods. The present findings would assist the decision makers to propose management strategies and regulations on the harvesting of P. lividus off the Egyptian Mediterranean coast.

Growth rates and health status of fish have been positively affected by adding dietary brown algae Padina pavonica as a meal. The present study aims to investigate the effects of P. pavonica on growth performance, hematology, biochemistry, and kidney and liver status of Nile tilapia (Oreochromis niloticus). The diets of Nile tilapia, with an initial weight of 4.58 ± 0.03 g, were enriched with 2.0, 4.0, 6.0 and 8.0 g/kg of P. pavonica concentrations for 45 days. This study was performed under two different conditions, i.e., experimental environment (A) and farming environment (B). At the end of the trial, the parameters of growth performance showed a significant difference between groups in experimental environment. However, they showed no significant difference in farming environment. The highest growth recorded with higher concentrations of P. pavonica diets (8.0 g/kg) as compared to their control in farming environment. In terms of hematological and biochemical parameters, this study revealed that there were highly significant differences (p ≤ 0.05) between the treated and control groups, with higher concentrations of algal meals (8.0 g/kg), in both farming and experimental environments.

Ecosystem health can be monitored by analyzing the species diversity and abundance in a region. The process of recognizing species based on morphology takes a lot of time and expertise. Metabarcoding and other modern molecular taxonomic methods can help speed up species identification. However, the choice of gene markers and primers, the lack of reference sequences in public databases, and the choice of tools used in bioinformatic analyses have a substantial impact on the observed diversity. To test the effectiveness of metabarcoding in assessing the species diversity, mock communities of zooplankton species found in the Saudi Arabian Gulf were assembled and subjected to high-throughput sequencing (HTS) using an Illumina MiSeq platform. Short CO1 and 28S nuclear gene fragments, containing the D2 region, of lengths 313 bp and 400 bp, respectively, were used as gene markers. Trimmomatic, Cutadapt, the FLASH read-merge software tool, and the USEARCH pipeline for OTU clustering were used in the bioinformatic analyses. Around 90% of the zooplankton species in the mock communities were detected. We conclude that the combination of CO1 and 28S markers is a quick and effective tool for evaluating zooplankton species diversity.