Egyptian Journal of Aquatic Research最新文献

The taxonomic and functional diversities of macroinvertebrates are a critical indicator of ecosystem health. This study focuses on the taxonomic and functional diversities of the assemblage structure of macroinvertebrates in the Ibrahimia Canal, Egypt. They were compared across two different substrate habitats: sediment-associated and macrophytes-associated habitats. Significant variations in the taxonomic and biological trait community composition in the two substrate habitats were recorded, with high taxa abundance in sediment substrate and increased diversity in macrophyte substrate. In sediment substrates, burrow dweller and collector-filterer taxa were the main characteristics, while tube dweller and collector-gatherer were the main traits of macrophytes substrate. The taxonomic and functional indices tended to increase from sediment to macrophytes substrate; however, there was an increase in Rao’s quadratic entropy index (RaoQ) for sediment substrate habitat. Redundancy analyses explained the association between environmental factors and macroinvertebrate taxa and traits. Total suspended solids, dissolved oxygen, chemical demand oxygen, and phosphate were the key environmental drivers of the taxonomic and functional diversities of macroinvertebrates. Integration between the approaches to taxonomic and functional diversity is recommended to give insight into explaining and managing the freshwater ecosystem.

This study aims to document the first occurrence of the epipelagic amphipod Cranocephalus scleroticus (Streets, 1878) in the Egyptian Mediterranean waters. During the winter of 2019, only one female specimen was collected by a zooplankton net from El-Dabaa sector on the western coast of Egypt. An investigation of systematic position and concise redescription, along with some structural photos, was conducted to confirm the identification. Habitat and distribution are also provided in the study. A new record, that has never been recorded before, is added to the list of species of the Egyptian Mediterranean fauna.

Marine ecosystems are full of unique microbial phenomena, among them bioluminescence that could be harnessed for different ecological functions. This study was conducted to isolate luminous bacteria and utilize their glowing properties as a potential biosensor for toxicity assessment designs. It is worth noting that this study is the first report on the isolation of an Octopus associated Photobacterium species from Alexandria, Egypt. Based on light intensity, strain Photobacterium sp. EAH3 was selected and identified using 16S-rRNA gene sequencing. The luminescence production was further optimized using experimental. Among eight tested variables, the Plackett-Burman design showed that yeast extract, glycerol, peptone, and NaCl were the most important factors affecting luminescence. The central composite design calculated the optimum concentration of these variables in the optimized medium, which enhanced the bioluminescence activity by 1.39 folds. The employment of Photobacterium sp. EAH3 as a biosensor for the toxicity assessment of some solvents, hydrocarbons and heavy metals was examined using bioluminescence inhibition assay. According to the IC₅₀ results, the highest toxicity values recorded were 0.004 M, 4.15 ppm and 1.4 ppm for isoamyl alcohol, Hg²⁺ and catechol, respectively. Moreover, our study sheds light on futuristic methodology for monitoring toxicity in real polluted environmental and effluents' samples reflecting its promising efficiency.

Glossogobius aureus (Gobiiformes: Gobiidae) is a target fish and widely distributed in the Mekong Delta, from fresh to brackish waters. However, knowledge on its food and feeding ecology is scarce. Therefore, this research was carried out in four sampling sites along the estuarine of Hau River in order to fill this information gap. A total of 742 individual fish was collected monthly using trawl nets from January to December 2020. A combined analysis of the fullness index and Costello graph suggested that this fish species displayed high feeding intensity. The results revealed that G. aureus is a carnivore and its food composition comprised Acetes spp., Actinopterygii, zooplankton, and other preys (e.g. snails and detritus). Acetes spp. is the main food of this species. The diet composition varied with sites but not genders, fish sizes, and seasons. Acetes spp., Actinopterygii and other preys contributed to the spatial variation of food composition. The findings revealed knowledge about the fish feeding ecology, which may propose suitable foods for its aquaculture development.

A total number of 100 Nemipterus japonicus was collected randomly from the Western Gulf of Suez, Red Sea, Egypt from September to April 2021. After external and internal examinations, two species of parasites were found. The first species was Mothocya melanosticta isopods (both sexes) with a prevalence of 52% and attached externally to the gills and inside the buccal cavity. The second species, Hysterothylacium aduncum nematodes that was found in three types of distributions in 53 fishes. Firstly, adults were found in the gastrointestinal (GI) tract with a high prevalence of about 58%. Secondly, larval stages were found in 52 fishes with a high prevalence of about 57%. Thirdly, adults and larvae were found mixed together in 91 fishes with a high prevalence of 91% inside the GI tract of the same host. There was mixed infestations with M. melanosticta and H. aduncum with a percentage of 51% with several observed signs on the infested fishes. To determine the correct identification of detected parasites, both species were subjected to morphological and electron microscopic examination. Based on the present findings, further studies are recommended on the host-parasites relationship.

Length-weight relationships (LWRs) are pivotal for comparative life-history studies, conservation strategies and ecosystem modelling among regions. They provide essential information on the growth, fitness and wellbeing of a population in an ecosystem. Length and weight relationships and descriptive statistics for eight Chondrichthyes, caught off the Madeira archipelago between 2004 and 2019 from depths ranging from 350 to 2500 m, are herein reported. A total of 767 specimens was studied and it was observed that the parameter b (relative growth rate) oscillated between 2.558 for males of Centrophorus squamosus and 3.494 for females of Etmopterus princeps. This study is the first to include the LWRs for these 8 Chondrichthyes species in Madeira waters.

Pollution rates in ports areas should be monitored on a regular basis in order to protect marine environment. This study focused on the inhibitory effects of copper and zinc, and cybutryne (an antifouling agent) discharged from the dry-dock cleaning process of ship hulls on the growth and amino acid content of Dunaliella salina, a unicellular green marine alga. In addition, the metal concentrations in effluents were assessed in order to know the potential threats and possible consequences of the effluent discharge on the marine habitats. The antifouling cybutryne was found to be the most potent inhibitor of growth and amino acid content in D. salina, followed by copper and zinc, which were present at very high concentrations in the study area. However, the lowest concentration (5 mg/L) of the two heavy metals increased the algae growth and amino acid content, and the results showed that Cu²⁺ produced more growth inhibition effect on D. salina than Zn²⁺.

The European seabass Dicentrarchus labrax, Europe's first commercially farmed non-salmonid fish and the most farmed Mediterranean fish, with Egypt as a major producer, is susceptible to several diseases, one of which being copepod infestation. Lernanthropus kroyeri (Beneden 1851) is a parasitic copepod that can be found across the Mediterranean Sea. Little research on L. kroyeri has been done along the Mediterranean Sea off the Egyptian coasts. In the current investigation, gill filaments, particularly those of the second-gill arch, were found to be infested with parasites with a prevalence rate of 23%. They were morphologically identical and confirmed as members of the family Lernanthropidae, having the characteristic features of L. kroyeri. Scanning electron microscopy (SEM) was used to examine morphological traits. Clinical and histological evidence of the parasite's catastrophic impact on infected fish has been described. DNA sequencing of the parasite's mitochondrial COI gene proved its identity, and it was the first of L. kroyeri to be added to the GenBank database, with the accession number MZ726776. The phylogenetic analysis revealed that the parasites arose from a monophyletic group that is distinct from other Lernanthropidae family members.

Environmental enrichment (EE) is an important factor that helps improve both the physical and psychological behavior of farmed animals. This factor also controls social interactions and provides more stimulants to influence the reproductive performance of animals in captivity. As EE plays an important role in animal reproduction, the present study was designed to investigate the effects of different types of tank bottom enrichments on the ovarian development of Buitta (Sperata sp.) catfish in captivity. Barren (T_A), muddy (T_B), and sandy (T_C) enrichments were utilized for four months to observe the physical and psychological changes of the catfish. The results showed significant differences (p < 0.05) in the weight gain, gonadosomatic index (GSI), and hepatosomatic index (HSI) of the fish, however, no significant difference was found in the fish fecundity. The most prominent changes include weight, ripeness, the biochemical composition of body tissues, and the frequency distribution of the migratory nucleus in the oocytes. Moreover, the diameter of oocytes that occurred in the enrichment T_C (p < 0.05) was significantly higher than the enrichments T_A and T_B. Histological observation found at least two stages of the ovarian oocytes development process in each ovary indicating the asynchronous self-reproduction of the fish. Additionally, biological macromolecules analysis found higher protein content in the muscle (86.04%), liver (52.97%), and oocyte (64.71%) and a higher deposition of lipid within the oocytes (32.33%) and liver (27.06%) for enrichment T_C, while these values were lower for the other two treatments. Finally, the study suggests that a sandy environment should be used to obtain an acceptable level of oocyte development in the female Buitta fish in captivity.

The current study presents the first bathymetric map of Toshka Lakes in Egypt using the bathymetric method that is based on the combination of in situ measurements, Remote Sensing, and GIS technologies. Such a combination allows an accurate determination of the three-dimensional shapes and volumes of inland water basins, as shown by its implementation in the survey of the Toshka Lakes. The determined total surface area of the Toshka Lakes is 2321.64 km², holding a cumulative capacity of 53.28 billion m³ (almost equal to Egypt’s annual water income from the Nile). Being today the Toshka Lakes in a mature stage, the results of the morphometric and hypsometric analyses provide useful information for water conservation. The lakes are also expected to gradually shrink in size, similar to what happened in the past decades. Therefore, besides providing a digital database useful for water management, the proposed study is fundamental for appraising, with more realistic expectations, the future changes in the water basins in the Toshka Depression. This article documents the current status of the Lakes and enables researchers and decision-makers to predict their changes in volume and area with depth in the future.