Bilateral asymmetry is presumed to reveal the developmental variability of the fish in polluted aquatic environments. In these habitats, high-level asymmetry develops, and these fish expend more energy to balance their growth than fish that are not under an impact. A total of 210 specimens of Acanthopagrus bifasciatus, A. latus and Sparidentex hasta were collected from the marine waters of Iraq in the northwest part of the Arabian Gulf. The asymmetry was calculated for the sagittal otolith characters of length and width. Otolith width has lower asymmetry than otolith length for the three sparid fish species investigated. An increase in the value of fluctuating asymmetry with fish length was observed. This could be a pertinent indicator of pollution in the habitat.

The harmful alga Chattonella marina has caused massive fish kills and economic losses worldwide. However, the fish kill mechanisms by C. marina have not been identified. The present study has confirmed that a significant elevation of blood osmolality is the universal response in moribund fish exposed to C. marina and the possible reasons leading to contradictory reports were identified. Both osmotic distress and respiratory impairment are important mechanisms leading to fish kill by C. marina. The susceptibility of marine fish to C. marina appears to be inversely related to their tolerance to hypoxia, with the hypoxia intolerant goldlined seabream being the most susceptible, and the hypoxia tolerant green grouper being the most tolerant to C. marina. Further studies in the marine medaka (Oryzias melastigma) showed that fish susceptibility to C. marina is directly related to susceptibility of the fish to hypoxia, but not related to its tolerance to hypersalinity stress.

Saccular otolith mass asymmetry is examined in three sparid fish species, Acanthopagrus bifasciatus, A. arabicus, and Sparidentex hasta collected from Khor Abdullah at the North Persian Gulf. This characteristic was computed as the disparity between the weight of the right and left otoliths divided by mean otolith weight in the three sparid species investigated. According to the previous cases obtained on another symmetrical fish species, the absolute value of x in these species does not determine by fish length and otolith growth ratio, while the absolute rate of otolith weight disparity is boosted with the fish length. The estimate of x was between -0.2 and +0.2. Otolith mass asymmetry can show some growth disorder of fish owing to environmental influence.

Previous laboratory feeding experiments, representing the state-of-the-art methodology to investigate microplastic (MP) ingestion and its impact for fish, tend to disregard both the significance of applying realistic MP densities and the potential relevance of biofilm-coating for ingestion probability. This experiment assessed the uptake of either pristine or biofilm-coated MP particles and the physiological impacts for juvenile white seabream for MP concentrations consistent with those found in the field along with natural prey over a course of 3.5 weeks. Results indicate the ability of juvenile D. sargus to discriminate between edible and non-edible prey. A distinct preference for biofilm-coated over pristine particles could not be verified. No significant impact on growth and condition was found except for high levels of MP ingestion. The outcomes highlight the importance of performing MP feeding experiments mimicking natural conditions to reliably assess the impact of MP on early life stages of fish.

The aims of this study were to investigate the presence of Staphylococcus aureus and staphylococcal enterotoxins, as well as Salmonella spp. and to determine the antimicrobial susceptibilities of the isolates from fish samples. A total of 100 fish samples were analysed consisting of 30 anchovy, 35 trout and 35 sea bream. The presence of SEs was detected using ELISA and its genes confirmed by mPCR. Also, S. aureus and Salmonella spp. were detected in 9 (9%) and 5 (5%) samples, respectively. None of the S. aureus isolates had SEs and SEs genes. The resistance rates of the S. aureus isolates to erythromycin, tetracycline, and penicillin G were found to be 33% while Salmonella spp. isolates were resistant to trimethoprim-sulfamethoxazole, gentamicin and neomycine in 20%, 20% and 80%, respectively of the samples. It is of utmost important for public health that retail fish markets need to use hygienic practices in handling and processing operations.

In aquacultures, heavy metals could be accumulated in fish tissues from natural and human-related sources depending on different factors. This study aims to estimate the level of bioaccumulation of heavy metals in cultured Gilt-head sea bream Sparusaurata. In this regard, heavy metals concentrations were measured in both water and fish musculature that were collected from a private fish farm in Kafr ElSheikh, Egypt. Regarding the water samples, heavy metals were within the permissible limits with exception of Cd, Cu, and Zn. In fish musculature, all heavy metals were within the WHO/FAO permissible limits. The bioaccumulation factor (BAF) indicated that mostly all heavy metals accumulation in the Gilt-head sea bream musculature decreased with time which may be correlated with the increase in water pH, calcium, and other cations concentrations. The hazard index (HI) calculations indicate no adverse health effects of heavy metals on humans through daily fish consumption so far. However, health risks are not negligible making the regular monitoring of metal contaminants in the studied area a necessity.

Organochlorinated pesticides and Aroclors were measured in the muscle of two edible fish species (gray mullet, sea bream) and blue crab, collected from eastern Mediterranean coast in 2013. The concentration of organochlorinated pesticides (OCPs) and Aroclors in biota samples which were collected at six sites ranged from 1.0–8.6 and 9–47.5 ng g⁻¹ wet weight, respectively. Total DDT concentrations in seafood samples were compared to tolerance level established by the US Food and Drug Administration (FDA); the concentrations were detected below the tolerence level. Health risk assessment was conducted related to the consumption of chemically contaminated seafood. The estimated daily intake of OCPs calculated by using the estimated daily fish consumption in Turkey was far below the acceptable daily intake as established by FAO/WHO. Our data indicated that consumption of blue crab, gray mullet, and sea bream collected from the Mediterranean coast of Turkey could pose “no risk” for human health in terms of OCPs.