Search Results (8)

This study aims to enhance our understanding of the marbled spinefoot (Siganus rivulatus) population along the Red Sea coast of Saudi Arabia. It investigates whether the stock is subject to overfishing and tests the hypothesis that current fishing mortality exceeds sustainable thresholds. A total of 6192 specimens were sampled during a comprehensive survey conducted from 2022 to 2024, utilizing a range of fishing methods, including handline, trap, gillnet, and demersal trawl fisheries. The sampled fish ranged in total length (TL) from 100 to 335 mm and in total weight (W) from 17 to 470 g. The length–weight relationship was W = 0.0175 × TL^2.92. Growth parameters derived from the von Bertalanffy model were TL_∞ = 43.5 cm, K = 1.12 year⁻¹, and t₀ = −0.18 year. The median size at first maturity was estimated at 14.83 cm TL for both sexes. Virtual Population Analysis revealed fishing mortality rates ranging from 0.01 year⁻¹ to 0.89 year⁻¹ across age classes 1 to 5 years, with exploitation levels of 0.6, 0.55, and 0.5 at ages 3, 4, and 5, respectively, indicating slight overfishing. The annual average catch of marbled spinefoot along the Saudi Arabian Red Sea coast was approximately 211 tonnes, contributing an estimated 1.8 million USD to the national economy. Maintaining the current fishing effort at sustainable levels is essential to ensure the long-term viability of this stock. Full article

Microplastics (MPs), defined as plastic particles smaller than 5 mm, have emerged as a global environmental and public health crisis, infiltrating air, water, soil, and food systems worldwide. MPs originate from the breakdown of larger plastic debris, single-use plastics, and industrial processes, entering food. Emerging evidence underscores the ability of MPs to cross biological barriers, including the blood–brain barrier, triggering neuroinflammatory responses and contributing to neurodegenerative diseases such as Alzheimer’s and Parkinson’s. Polystyrene (PS), a common type of MP, activates microglial cells, releasing pro-inflammatory cytokines like tumor necrosis factor (TNF-α) and interleukins, which increase neuronal damage. MPs have also been linked to cardiovascular diseases, with studies detecting polyethylene (PE) and polyvinyl chloride (PVC) in carotid artery plaques, increasing the risk of myocardial infarction and stroke. Furthermore, MPs disrupt endocrine function, alter lipid metabolism, and induce gut microbiome imbalances, posing multifaceted health risks. In the MENA region, MP pollution is particularly severe, with the Mediterranean Sea receiving an estimated 570,000 tons of plastic annually, equivalent to 33,800 plastic bottles per minute. Studies in Egypt, Lebanon, and Tunisia document high MP concentrations in marine ecosystems, with herbivorous fish like Siganus rivulatus containing over 1000 MPs per individual due to the ingestion of contaminated seaweed. Despite these findings, public awareness and regulatory frameworks remain inadequate, with only 24% of Egyptians demonstrating sufficient knowledge of safe plastic use. This review emphasizes the urgent need for region-specific research, policy interventions, and public awareness campaigns to address MP pollution. Recommendations include sustainable waste management practices, the promotion of biodegradable alternatives, and enhanced monitoring systems to mitigate the health and environmental impacts of MPs in the MENA region. Full article

The management of biological invasions is among the most urgent of global challenges and requires a significant monitoring effort to obtain the information needed to take the appropriate decisions. To complement standard monitoring, citizen science is increasingly being used. Within citizen science, the approach of collecting and investigating Local Ecological Knowledge (LEK) proved to be useful in the monitoring of non-native species. A LEK survey was carried out in 10 Sicilian and Maltese Natura 2000 sites in order to help in the early detection of non-native species. The survey was addressed to local fishers and SCUBA divers in order to investigate the occurrence of 24 selected marine non-native species and to identify potential hotspot areas of invasion through the use of six indicators: the occurrence of newly introduced nonindigenous species, the cumulative impacts of invasive alien species (CIMPAL) and the relative importance of species on the cumulative impacts (D1, D2, D3, and D4). The respondents confirmed the presence of 22 species since the year 2000 and reported 10 new ones registered in the investigated areas. The highest CIMPAL value was observed in two Sicilian Natura 2000 sites (ITA090028 and ITA040014) and the lowest on the western coast of Malta (MT0000101, MT0000102, MT0000103, and MT0000104) The four top-priority species according to indicators D1–D4 were Caulerpa cylindracea, C. taxifolia, Siganus luridus and S. rivulatus. The study produced a valid and useful scientific output to suggest and address management strategies to monitor the establishment of the non-native species. Full article

Biological invasions are a human-induced environmental disturbance that can cause major changes in ecosystem structure and functioning. Located in the northeastern Mediterranean basin, the Aegean Sea is a hotspot of biological invasions. Although the presence of alien species in the Aegean has been studied and monitored, no assessment has been conducted on their cumulative impacts on native biodiversity. To address this gap, we applied the CIMPAL index, a framework developed for mapping the cumulative impacts of invasive species, to identify the most affected areas and habitat types and determine the most invasive species in the region. Coastal areas showed stronger impacts than the open sea. The highest CIMPAL scores were four times more frequent in the South than in the North Aegean. Shallow (0–60 m) hard substrates were the most heavily impacted habitat type, followed by shallow soft substrates and seagrass meadows. We identified Caulerpa cylindracea, Lophocladia lallemandii, Siganus luridus, Siganus rivulatus, and Womersleyella setacea as the most impactful species across their range of occurrence in the Aegean but rankings varied depending on the habitat type and impact indicator applied. Our assessment can support marine managers in prioritizing decisions and actions to control biological invasions and mitigate their impacts. Full article

A big number of Red Sea species have entered the Mediterranean Sea since the opening of the Suez Canal. Some of them quickly establish local populations and increase their abundance, forming a potential threat for local biodiversity and fisheries. Here, we use habitat modeling tools to study the expansion of three alien, demersal fish species that entered the Mediterranean basin at different times: Pterois miles, Siganus luridus and Siganus rivulatus. Georeferenced occurrence data from the eastern Mediterranean over the past ten years were compiled using online sources, published scientific literature and questionnaires and were correlated with environmental and topographic variables. The maximum entropy modeling approach was applied to construct habitat suitability maps for the target species over all of the Greek Seas. Results emphasized the three species’ strong coastal nature and their association with the presence of Posidonia oceanica meadows. Probability maps evidenced that for all species there is a higher likelihood of presence along the southeast and central Aegean and Ionian Sea coasts and a lower likelihood throughout the North Aegean Sea. For Siganus spp., predictions in the Thracian Sea were highlighted as highly uncertain, as the environmental conditions in this area partly fall outside the range of values occurring in locations of their current presence. Full article

Toxic metal pollutants in aquatic environments negatively affect the natural characteristics of water and living organisms. Herein, 254 and 232 specimens (8–14/month) of the fish Siganus rivulatus (Teleostei: Siganidae) were caught alive during four successive seasons in the Red Sea, Egypt, from a chronically polluted bay and from an unpolluted bay, respectively. In each bay, the monthly water temperature was recorded, and the seasonal concentrations of Cd and Pb were determined in the water and in the intestine, liver, and gonads of both fish sexes. In the polluted bay, Cd and Pb were found in significantly high concentrations in the water and in the fish’s intestine, liver, and gonads, and the concentrations only significantly increased in the fish gonads during the spring (spawning season). In each bay, seasonal levels of sex steroid hormones (testosterone T, 17β-estradiol E₂, and progesterone P4) in both fish sexes were determined, and they only peaked in both sexes during the spring. In male fish, the serum levels of these hormones throughout the year were in the order T > E2 > P4, while in the females, they were in the order E2 > T > P4. Compared to those in the fish from the unpolluted bay, the levels of these hormones in the fish from the polluted bay were greatly altered. Our results strongly suggest that the serum levels of sex steroid hormones are sensitive biomarkers for detecting heavy metal pollutants in aquatic environments and their effect on fish reproduction. Full article

Toxic metal pollutants in aquatic environments and infestationwith intestinal helminths adversely affect the fish health, as well as fish consumers. Acanthocephalan worms in fish intestine have a high potential to absorb and bioaccumulate different heavy metals, especially toxic ones, from the intestine via their tegument with greater efficiency than the fish intestinal wall. Herein, 47 specimens of the fish Siganusrivulatus were trapped in the Red Sea, Egypt, from a chronically polluted bay. All were intoxicatedwith Cd and Pb; 20 (42.5%) were uninfected with any intestinal worm, but the other 27 (57.5%) were infected only by the intestinal acanthocephalan Sclerocollum rubrimaris. The number of individual worms in a fish host (infrapopulation size) ranged from 32 to 236. As a reference group, 22 uncontaminated–uninfected specimens of S. rivulatus were trapped from a small unpolluted bay. Our results revealed that infection with acanthocephalans alleviatesthe harmful effectsof toxic metalson their fish hosts by: (1) lowering the elevated concentrations of both Cd and Pb in fish liver; (2) lowering the elevated levels of liver enzymes (ALT, AST, ALP, and GGT), glucose, triglycerides, and urea in fish blood serum; and (3) raising the declined levels of total protein and albumin in fish blood serum. All of these were dependent on S. rubrimaris infrapopulation size in fish intestine. Full article

A 60-day feeding trial was conducted to assess the effects of dietary supplementation with bile salts (BS), lutein (LTN), and their combination on growth, survival, carotenoid content, and antioxidant status of rabbitfish (Siganus rivulatus) larvae. Fish were fed four isonitrogenous (34.39% protein) and isoenergetic (20.57 kJ/g) diets supplemented with BS (0.15 g kg⁻¹), LTN (0.1 g kg⁻¹), BS+LTN (0.15 and 0.1 g kg⁻¹, respectively), and a non-supplemented control diet. The results revealed that fish fed BS+LTN had the highest significant specific growth rate (4.37% day⁻¹), feed efficiency (46.55%), and survival (97.78%). Lutein supplementation improved whole-body protein content, meanwhile, fish fed a BS-supplemented diet had a higher lipid content. The carotenoid deposition was significantly increased with LTN and BS+LTN in skin, muscle, and whole body compared to the control and BS treatment. All dietary supplementation of BS and LTN showed significant improvement in total antioxidant capacity, catalase, and glutathione peroxidase activities. Additionally, LTN alone or BS+LTN significantly reduced malondialdehyde levels by 5.30 and 29.91%, respectively compared to the control. BS supplementation modulated aminopeptidases activities, triglycerides, cholesterol, and increased the activity of pancreatic lipase. Therefore, it could be inferred that dietary supplementation with LTN in combination with BS could improve the growth performance, carotenoid deposition, antioxidant status, lipid digestion, and metabolism of S. rivulatus. Full article