Egyptian Journal of Aquatic Research最新文献

The present work reported the length-weight relationship of four deep-sea chondrichthyan species (i.e., Hydrolagus spp., E. granulosus, C. owstonii and C. squamosus) captured by the experimental fishery of the depth cod (Dissostichus eleginoides) in Ecuadorian oceanic waters, from 2018 to 2020. The fishing included 592 hauls, starting at 1,000 m depth, using between 1,000 to 1,500 N° 14/0 circle hooks. Length-weight relationship (LWR) was estimated by the power model (y = ax^b). The determination coefficient (r²) value was always above 0.94. The slope (b) showed negative allometric growth (b < 3) for females of C. owstonii, C. squamosus and males of E. granulosus and Hydrolagus spp. Allometry was positive (b > 3) in females of E. granulosus and Hydrolagus spp. as well as, in males of C. owstonii and C squamosus. In addition, the allometry for the combined sexes was negative in C. owstonii and was positive in C. squamosus and E. granulosus.

The present study was planned to explore the effect of bio-fermentation on the fatty acid profile and the pattern of biogenic amines in salted grey mullet 'fessiekh' compared to the traditionally fermented ones. The results revealed that bio-fermented fessiekh showed significantly lower saturated fatty acids with significantly higher mono- and polyunsaturated acid contents than the control treatment. The lactic acid bacteria Lactobacillus casei and L. helveticus were beneficial resulting in a substantial reduction in saturated acids and a rise in unsaturated acids in comparison with Lactococcus cremoris. The results also revealed that bio-fermented fessiekh had significantly lower concentrations of all examined biogenic amines except spermidine and spermine that increased in bio-fermented fessiekh than the control. Both lactobacilli showed potent reducing activities on the formation of different biogenic amines during fessiekh processing than L. cremoris. B-phenyl ethyl amine and putrescine exceeded the permissible limits in the control group on the 7th day of the salting period, while the bio-fermented fessiekh showed acceptable values until the end of the salting process. We conclude that LAB can improve the fatty acid profile of fessiekh and reduce the buildup of biogenic amines in this product to safe and acceptable levels.

The Nile Delta is the oldest delta in the Mediterranean Basin, situated in the middle of its eastern geodynamics progress. It represents a major strategic area for Egypt. Beside the Mediterranean Sea level rise, the Nile Delta may suffer from subsidence due to the reduction of the sediments supply after building the Aswan High Dam. In addition, oil and gas production plays an effective role in the Delta deformation. Nowadays, monitoring the Delta's crustal deformation is regarded as one of the most essential interests for research studies due to the strategic importance of the huge landform created by the Nile. This research aims to determine and interpret the crustal movements for the Nile Delta either locally or regionally using GNSS data during the period 2013-2020. For this purpose, data from 14 GNSS permanent stations were analyzed. The results showed that the Delta is characterized by heterogeneous movements. The local horizontal movement rate is averaged by 2.5 mm per year, which represents a low rate. In addition, the eastern and western sides of the Delta showed different geodynamic behavior related to its structural properties. The vertical velocities showed a significant subsidence ranging from -0.11 mm per year at Helwan to -9.1 mm at Mansoura.

Lake Qarun is one of the oldest lakes in the world, a prehistoric lake, from the era of the pharaohs. It started as a freshwater lake and nowadays changed to become a saline lake due to climate changes and anthropogenic activities. Currently, the lake is facing big challenges, affecting the sustainability of its natural bioresources. The lake ecosystem passed by successive changes since the beginning of the 19th century that have led to drastic changes in its elements. In addition, it was subjected to different exploitation regimes. During the last decade, its fisheries production sharply declined and the fate of the lake became unclear due to many factors, some were recognized and a lot were unrecognized. To overcome the present situation, governmental agencies and scientific communities should find a viable way to stop the deterioration of the lake's ecosystem and restore the collapsed fish production. The current review casts the light on the entangled history of the lake to come up with a coherent concept for the recovery and rehabilitation of Lake Qarun bioresources. We proposed an integrated management plan for the lake's ecosystem rehabilitation to ensure sustainable exploitation of the lake's fish resources.

This study was conducted to estimate some biological aspects and fisheries assessment of Diplodus vulgaris caught by gillnets during the period 2018–2020 from the Egyptian Mediterranean waters of Alexandria. From an overall of 1004 individuals of D. vulgaris (10.0 – 24.0 cm TL) examined, lengths from 13.0 to 17.0 cm were representing 82.67% of the total fish number. The length-weight relationships for total and gutted weights of the D. vulgaris were: Log W = −1.7144 + 2.9063 Log L (R² = 0.9982) and Log W = −1.8508 + 2.9903 Log L (R² = 0.9967), respectively. The condition factor (k) was found to be fluctuating between 1.268 and 1.534 with an average value of 1.395 ± 0.0597. The overall sex ratio (M: F) was 1.00: 0.63 and the chi-square test revealed highly significant difference (χ² = 24.80; df = 1; P < 0.01). The spawning season of D. vulgaris was observed from December to February for both sexes. The gonadosomatic index (GSI) reached its highest value in December for both sexes. The age composition of the D. vulgaris catch was estimated to be four years and the first age dominated the population. The present von Bertalanffy growth parameters were calculated as follows: the coefficient of growth (K) = 0.128 yr.^-1, the asymptotic length (L_∞) = 37.06 cm, and the hypothetical age at zero size (t_o) = −2.773 yr.^-1. The growth performance index (Ф') was: Ф'_L = 2.24, and Ф'_W = 1.00. The reproductive load (L_m/L_∞) was low for males (0.39) and females (0.37). The ratio L_max^D/ L_m^D was 1.36 and 1.39 for males and females, respectively and it was found to be compatible with the Pauly's Gill-Oxygen Limitation Theory (GOLT). The total mortality coefficient (Z) was 1.79, the natural mortality (M) was 0.39 and fishing mortality (F) was 1.40. The M/K was 3.0615 and Lc/L_∞ was 0.371. At the level of the current exploitation rate (E_cur = 0.78), the stock is considered highly exploited by gillnets fishery and only 9.34% of the stock biomass is protected. Fishery management for this wild stock is highly required.

The coastal areas of the Red Sea within Saudi Arabia have a wide diversity of marine soft corals harboring many symbiotic bacteria that could present a potential source of many antibacterial metabolites. This study focused on the molecular characterization of antibiotic-producing bacteria associated with soft corals and investigated the influence of culture conditions on the production of their antibacterial extracts. Two soft coral samples were collected offshore from Yanbu City and identified as genus Sarcophyton. Screening for antibiotic-producing bacterial symbionts uncovered nine isolates with a wide inhibitory spectrum against gram-positive and negative bacteria. Phylogenetic analysis of the bioactive bacterial symbionts 16S rRNA gene sequences revealed the prevalence of gram-negative bacteria with seven isolates all belonging to class γ-proteobacteria. The remaining two isolates were represented within class firmicutes and actinobacteria. Eight isolates were grouped perfectly with their best matches. While the remaining ninth isolate was phylogenetically separated from all the species within the Photobacterium genus, suggesting that it could be a novel species. The optimum antibacterial compounds production was obtained in minimal media, at a temperature range of 25–28 °C, pH 7 and 100–150 rev/min agitation during 24–48 h of the incubation period, with moderate to high degree of thermal stability.

Microplastics are omnipresent in the marine environment. Their bioaccumulation in fish and other marine biota is a concern due to the potential human health risks from exposure through seafood sold in markets. There is a global effort afoot to take inventory of microplastic contamination in the world’s main water bodies. This includes an understanding of the sources, the trophic transfer and the fate of microplastics in aquatic systems. Studies on the state of microplastic pollution in the Red Sea have appeared only in the last 5 years. Nevertheless, they gave insight into the abundance of microplastic particles within the marine environment of the Red Sea. The following is a review of these studies.

This study aims to investigate the effect of cold (5 ± 2 °C) and ambient (33 ± 2 °C) storage conditions on the storage quality of anchovy fish (Engraulis encrasicolus) sauce. Fish samples were obtained from Qarun Lake, Egypt, during the summer of 2019. They were dry-salted with a salt content of 20% (w/w) and stored at a range of 28–32 °C for 60 days. Plain sauce was treated with 0.1% of garlic (Allium sativum), black seed (Nigella sativa), rosemary (Salvia rosmarinus) and jojoba (Simmondsia chinensis) extracts, and stored at different conditions. The results showed that the plain sauce had a pH of 6.17, total volatile basic nitrogen (TVB-N) of 72.23 mg/100 ml, free amino nitrogen (FAN) of 12.86 mg/100 ml, acid value (AV) of 0.63 mg KOH/ml oil, and free fatty acids (FFAs) of 0.66 mg/100 ml. Fish sauce with garlic was the best compared to others based on sensory evaluation. With regard to the effect of storage conditions on the efficacy of plant extracts, it was found that at 33 ± 2 °C jojoba, black seed and rosemary extracts controlled most quality indices, whereas at 5 ± 2 °C all extracts were more effective in controlling the quality indices of the anchovy sauce. In conclusion, this study suggests that plant extracts especially under cold storage could improve the storage quality and extended shelf life of anchovy sauce. In general, both storage conditions and periods affected the protein and lipid hydrolysis of the fish sauce samples. Fish sauce is safe for human consumption based on the international permissible values. In addition, the resultant dried cake can be exploited in the field of food industry as a value-added product.

The seasonal relationship between the physico-chemical characteristics and the macrobenthic fauna community was studied in Lake Qarun, Egypt. Lake Qarun receives a huge amount of agricultural drainage water from the neighboring cultivated land via El-Batts and El-Wadi drains. Generally, the obtained results have shown a decrease in dissolved oxygen, transparency and increase in COD, NO₃^– and NH₃ at the stations in front of El-Batts and El-Wadi drains due to the continuous pollutants discharged into the Lake's water. The WQI revealed that the water quality of Lake Qarun is poor for aquatic life. The macrobenthic community consisted of sixteen species belonging to three phyla, Mollusca (7 species) that was dominated by Cerastoderma glaucum, Annelida (4 species) that was dominated by Limnodrillus spp. and Arthropoda (5 species) that was dominated by Balanus pallidus. The structure and abundance of macrobenthic species were affected by many factors especially pollution from the drainage water contaminated with sewages, which affected all living organisms in the Lake. The WQI values of Lake Qarun ranged from 32.30 to 38.40 (poor class) and the average value in the whole area was 35.89 ± 1.64 that is ranked as poor for the aquatic life utilization. To avoid this undesirable effect, the pollutants that flow into the Lake must be treated before being discharged.

Crude and α- and β-cellulose yields were estimated in six macroalgal species belonging to various groups growing in the Mediterranean coast, Egypt. The extracted cellulose yield varied between 11.70% dry weight (DW) for Colpomenia sinuosa and 1.38% DW for Jania rubens. The results revealed that α-cellulose represented the major proportion “43%” to “74%” of cellulose, while β–cellulose represented the minor proportion “2.3%” to “12%”. Cellulose nanofibers (CNFs) were prepared from crude cellulose via acid hydrolysis, and the yield was calculated as “47.74%” to “9.13%”. The seaweed cellulose and CNFs of the maximum-producing species were morphologically characterized via scanning electron microscopy (SEM). The shapes of the extracted cellulose ranged from filaments and plates to web-like structures according to the seaweed species and cellulose fractions. The CNFs exhibited nanosphere shapes, with the average size ranging from 14.94 to 30.82 nm. Chemical analysis of the prepared cellulose performed via Fourier-transform infrared spectrometry (FTIR) demonstrated the similarity between crude and α- and β-cellulose. The CNFs were investigated via Ultraviolet–visible spectroscopy and surface plasmon resonance (SPR) bands, which confirmed the spherical shape of the prepared CNFs. In conclusion, the selected seaweeds can be used as a renewable source of dietary fibers and CNFs with economic applications. Further studies are required to screen numerous species of seaweeds for large-scale production of cellulose.