Egyptian Journal of Aquatic Research最新文献

Recently, nanotechnology-based paints have been employed in the field of biofouling prevention. The green production of copper oxide nanoparticles (GB-CuONPs) with Ulva fasciata water extract was described in this study. The aqueous U. fasciata extract contains diverse compounds that act as reducing and stabilizing agents for GB-CuONPs. The GB-CuONPs were characterized by different instruments. SEM indicated monoclinic phase (tenorite) clustered nanoparticles. EDX spectrum comprised C, N, Zn, Cu, and O peaks. FT-IR showed peaks that could be attributed to proteins, carbohydrates and polyphenols. The average crystallite size was 35.2 nm. XRD assigned the reflection lines of monoclinic GB-CuONPs. The antimicrobial activity of GB-CuONPs was studied against three Gram-negative and two Gram-positive bacterial strains. Antifouling efficacy of different concentrations (0, 0.25, 0.50, 1.00, and 1.50%) from GB-CuONPs was evaluated in situ for 200 days. Low weights of fouling organisms were formed on all the panels, ranging between 0.0495 and 0.1451 g/cm². Their effectiveness may be attributed to the biocide’s gradual release from the coatings. Panels treated with formulations containing (1.00% and 1.50%) GB-CuONPs showed good antifouling activity during the study period, with only 5% of barnacles. The surrounding seawater parameters of the immersed coated steel panels were within the typical range for this area.

In spite of the significance of trammel nets for small-scale fisheries (SSFs) in Egypt in what concerns landings, economic value, vessels and fishermen numbers, few studies on their size selectivity have been conducted. This study investigates the trammel nets’ size selectivity as a key métier of SSFs in three areas of Lake Nasser. A full survey of the commercially used trammel nets and experimental fishing trials using different models of trammel nets were carried out. The results of the survey indicated that the catch had a limited species variation, which included mango tilapia (Sarotherodon galilaeus), Nile tilapia (Oreochromis niloticus), and redbelly tilapia (Coptodon zillii). Regarding experimental fishing, four different mesh sizes (83, 95,108, and 120 mm) were applied and the nets selectivity curves indicated that the size-frequency distributions of all species showed shifting of the mean length to the right with increased mesh size in all nets. The best model was determined from the outcomes of model comparisons and it was the log-normal model for O. niloticus and bimodal for both S. galilaeus and C. zillii. This information can be useful in applying the technical measures for fisheries that depend on the trammel nets.

A 45-day feeding trial was conducted to assess the influence of Artemia (Artemia franciscana Vinh Chau) biomass and gut weed (Ulva intestinalis) meal as replacement protein sources for fishmeal (FM) and soybean (SB) protein on the performance of black tiger shrimp (Penaeus monodon) postlarvae (PL). The control diet did not include Artemia biomass or gut weed meal, and the experimental feeds were formulated to replace 20%, 40%, 60%, and 80% of the FM protein with Artemia biomass meal, combined with the replacement of 15%, 30%, 45%, and 60% of SB protein with gut weed meal. All the experimental feeds were similar in crude protein (40%) and lipid (7%) content, with three replicates per treatment. Shrimp PL with an average weight of 0.019 ± 0.001 g and length of 1.17 ± 0.02 cm were reared at a salinity of 10 ppt. The results showed that the survival of the shrimp was not significantly influenced by the feeding treatments (P > 0.05) and ranged from 81.1% to 86.7%. Interestingly, the growth rates in terms of the weight, feed efficiency, and resistance to formalin shock of the shrimp that were fed Artemia biomass and gut weed meal were superior to those that received the control feed. The study findings demonstrated that Artemia biomass combined with gut weed meal can replace up to 80% FM protein and 60% SB protein in the P. monodon PL diet. Notably, optimal shrimp performance was obtained using a 40% Artemia biomass and 30% gut weed protein replacement diet.

Expanding urbanization, socioeconomic factors, and agricultural activities have led to contamination of the natural water resources in Iraq. The objective of this study was to assess the riverbank filtration (RBF) process in purifying the water of Al-Kufa River from pathogens. The riverbank filtration is a natural approach that helps in the enhancement of the quality of river water, and it is a relatively cost-effective, and sustainable process. This study utilized microbiological approaches to monitor the water quality of wells in comparison with river water. In Al-Kufa district of Al-Najaf governorate in Iraq, eight wells were constructed at different locations adjacent to Al-Kufa River. Total plate count, coliform count, fungal count, and fecal coliform count were among the microbiological parameters tested. The findings of the current study showed a difference in the pathogen count between the wells and river water, but the riverbank filtration process did not meet the World Health Organization guidelines. From this, we concluded that, if the pumping well is continuously running, RBF as a preliminary treatment of surface water would be a promising and potentially viable application in purifying water supply. Finally, in future RBF process is supposed to be taken into consideration to protect the security of water supply from waterborne pathogens.

Urban expansion along the coastal sites is one of the major causes of the deterioration of mangrove habitats. This study aimed to report the current status of different mangrove environments in Saudi Arabia. Mangrove soil and sediment–water samples were collected from the coasts of the Arabian Gulf and the Red Sea for their physical, chemical, and heavy metal analysis. The mean values (n = 42) of heavy metals in the soil showed that Fe (2200 ppm) > Mn (91.9 ppm) > Zn (66.11 ppm) > Cr (62.40 ppm) > Ni (33.64 ppm) > Cu (31.06 ppm) > Pb (30.69 ppm) > Co (27.06 ppm). While the mean values (n = 15) of heavy metals in the sediment–water were as follows; Cr (0.1978 ppm) > Fe (0.1016 ppm) > Pb (0.0792 ppm) > Co (0.0706 ppm) > Mn (0.0356 ppm) > Cu (0.0317 ppm) > Ni (0.0215 ppm). The average values of Zn, Ni, Cu, Pb, and Co were greater than those reported previously in the Red Sea and Arabian Gulf coastal sediments. At the same time, Mo and Cd were not detected in any studied soil sample. The correlation analysis revealed that the EC of mangrove soil was positively correlated with SOM, Ca, Mg, Na, and K, while the EC of sediment–water was positively correlated with Na, K, and Cu. Landfilling, sewage pollution, mismanagement of solid waste, and contamination due to other anthropogenic activities may lead to heavy metal hazards and the loss of large areas of mangrove plants in this region. Therefore, the findings of this study should be considered to understand and design the management strategy of mangrove forests in the area of study.

New Borg El-Arab is a city located on the northwestern coast of Egypt, where the increasing anthropogenic activities have led to an increase in water demand. Groundwater is the main source of water in this area, but it is seriously affected by the Mediterranean saltwater intrusion. This causes a substantial impact on the water quality of the coastal aquifer. In this study, the electrical resistivity method was applied to delineate the shallow groundwater aquifer and its quality. Twenty vertical electrical soundings (VES) distributed along 6 profiles were measured. To observe the seasonal groundwater variations, 14 VES points were measured at the end of the rainy season, while the measurements of 6 VES points were repeated at the end of the dry season. The results revealed 4 geoelectrical layers; the first layer is a surface dry zone with variable resistivity values, followed by a water-bearing layer; while the third is a limestone layer, followed by a clay deposits zone. In comparison to the winter season, the water-bearing layer records lower resistivity values at the end of summer. Optimal locations to drill new groundwater wells have also been determined with a depth varying from 1.8 m north to about 30 m south.

The physicochemical and biophysical characteristics of the natural habitat of the African river prawn (Macrobrachium vollenhovenii) in the lower Volta River, Ghana, were surveyed as a prelude to assessing the optimal water quality requirement for hatching and larval rearing in captivity. Additionally, the fecundity of gravid females and incubation period were determined. The physicochemical and biophysical assessments were done at two sampling zones along the Volta River estuary. Gravid broodstock were collected from artisanal fishers, transported to a laboratory and maintained at 8 ppt until hatching. These females were used to estimate fecundity and determine incubation periods for M. vollenhovenii. A preliminary larval rearing trial was conducted at salinities of 0, 4, 8, 12, 16 and 20 ppt to determine the optimum range for growth and survival. The results from the study indicated that prawns were found from the littoral to the mid zones of the river where there were submerged aquatic plants. In terms of the water quality in the natural habitat of the prawn, the temperature, pH and dissolved oxygen levels were similar at the two zones (p > 0.05) but there were significant differences in salinity (p = 0.001), total dissolved solids (p = 0.001) and alkalinity (p = 0.003) levels at Ada Foah and Agave Afedome. The duration of egg incubation in M. vollenhovenii was 18 days, with eggs changing from orange at spawning to brown between the 9th and 14th day and grey between the 14th and 18th day before hatching. Fecundity ranged between 2,400 and 26,400 larvae per female. Although, hatching was successful, larval development could not proceed beyond the first larval stage owing to imbalances in the ionic ratios of minerals in the brackish water. Further studies are recommended to resolve the water quality challenges to ensure successful larval culture in captivity.

This paper used hourly data from the sea-level recorder installed in Port-Said Harbour on the Eastern Egyptian Mediterranean Coast. The data covered one decade (2002–2011) and were used to describe the temporal sea-level variability off Port Said including; its mean sea level (MSL), annual rate trend, seasonal behaviour, main tidal features, and the different water levels. The T_TIDE program was applied to obtain the astronomical constituents and the residual elevations. Throughout the period of study, the MSL was 69.1 cm; reaching its minimum (63.5 cm) in 2007 and its maximum (74.5 cm) in 2006. Tides were mixed mainly semidiurnal, and the sea level had an increasing rate of 2.1 mm/yr. The Principal Lunar constituent (M₂) had the largest astronomical amplitude of 13.4 cm, and the spring to neap ratio was 1.4. The sea level displayed seasonal alterations with the lowest values in spring and highest in summer. The residual heights varied between 11.60 and 110 cm with an average of 67.5 cm. Results revealed that the astronomical tide contributed with 2.3% in the observed sea level, while the surge contributed with 97.7%. The correlation between the sea-level fluctuations with the meteorological conditions in the vicinity of Port Said needs further investigation.

The present study elucidates the pattern of the reproductive activity of the invasive Pterygoplichthys disjunctivus male (n = 113) and female (n = 124) fish in Polgolla Reservoir, Sri Lanka. The reproductive activity was studied based on the gonadosomatic index (GSI), macroscopic and microscopic features of the testes and ovaries, and the serum testosterone and progesterone level during a 12-month study period. The monthly GSI of male fish (P = 0.0001) was the highest (0.333 ± 0.08%) in October and the lowest (0.044 ± 0.01%) in January whereas in the female fish, the GSI was not changed significantly (P = 0.1780) during the 12-month period of sampling. The mean monthly serum testosterone concentration (P = 0.0244) was the highest (0.396 ± 0.332 ng/ml) in March and the lowest (0.085 ± 0.156 ng/ml) in August, while the mean serum progesterone concentration of female fish showed no significant difference (P = 0.4798). Histological examination revealed that the testes with seminiferous tubules filled with sperm and the ovaries with mature oocytes were present throughout the year. Therefore, based on the results of histology and reproductive characteristics, we concluded that both male and female P. disjunctivus in Polgolla Reservoir are breeding throughout the year.

This investigation aims to study the reproductive traits, including sex ratio, spawning season and pattern, batch fecundity (F), and length at first maturity (L_m), of the commercial catfish Mystus mysticetus living in the freshwater of the Mekong and Chao Phraya basins. A collection of 596 individuals was caught using trawl nets from Cai Rang, Can Tho (CT) and Long Phu, Soc Trang (ST) from October 2020 to September 2021. The results showed a female-biased sex ratio (0.64 males: 1.00 females) and a pattern of multi-spawner as ripe ovaries contained different developmental stages of oocytes. A combined analysis of gonadal occurrence frequency and gonadosomatic index showed that this fish spawned during the wet season with a peak in June-July at CT and September-October at ST. The F ranged from 4,470–22,457 eggs/female (CT) to 4,104–23,651 eggs/female (ST) and these values increased with fish size. The egg diameter ranged from 0.63 ± 0.06 to 0.64 ± 0.06 SD mm, and L_m was higher in males (11.6 at CT and 11.2 at ST) than in females (10.9 at CT and 10.4 at ST). To conclude, it is recommended that the fish should be caught at length > L_m and avoid fishing in the main spawning period in order to exploit this fish resource sustainably.