Concentration and Exposure Assessment of Mercury in Commercial Fish and Other Seafood Marketed in Oman

The results of this study present analytical data of the mercury levels in several fish and shellfish species to create awareness among individuals of the risks associated with consuming fish contaminated with mercury. Mercury concentrations varied from a mean of 0.02 mg/kg in Indian mackerel to 0.19 mg/kg in shark in both fresh and frozen fish, from 0.02 mg/kg in sardines to 0.18 mg/kg in skipjack tuna in canned fish, and from 0.02 mg/kg in Indian mackerel to 0.79 mg/kg in shark in dried fish. Shellfish contained a slightly higher amount of mercury than fresh or frozen fish with a mean of 0.09 mg/kg. Trophic position, followed by habitat, was the most important factors for variability in mercury concentrations in fish and shellfish. The maximum safe weekly intake (MSWI) values of mercury were significantly higher for herbivores than for carnivores. The MSWI value for total mercury in the case of consuming most (72%) fish species was more than 5 kg; however, the MSWI value was never more than 5 kg in most (66%) shellfish species. Risks were identified upon consumption of 120 g of dried shark when exceeding the provisional tolerable weekly intake threshold (1.6 μg/kg) for methylmercury. Therefore, fish‐eating populations should reduce the quantity of dried shark to efficiently diminish the exposure to mercury.     

Fatty Acid Profile and Selected Chemical Contaminants in Yellowfin Tuna From the Arabian Sea

Fresh yellowfin tuna (n = 110) collected for a period of one year was analyzed for chemical composition, fatty acids, nutrients, and toxic metals. The mean values of investigated minerals were 892, 2834, 0.81, 6.61, 0.38, 11.0, 0.94, 0.59, 0.71, 0.53, and 0.29 mg kg^–1 for Na, K, Cu, Zn, Mn, Fe, Ni, Co, Cr, Sr, and V, respectively. Average Cd, Pb and Hg levels were 0.016, 0.029 and 0.137 mg kg^?1, respectively. The average concentrations of saturated, monounsaturated, and polyunsaturated fatty acids were 196.56, 84.8, and 218 mg 100g^–1, respectively. Yellowfin tuna contained higher DHA (148.2 mg 100g^–1) than EPA (29.3 mg 100 g^–1). A meal with 100 g of this species provides 48.6 and 71.05% of the required daily level of protein and EPA+DHA, respectively. Yellowfin tuna showed low thrombogenic (0.27) and atherogenic (0.43) potential and the value obtained for h/H index (1.97) indicates that regular intake of yellowfin tuna may bring hypocholesterolemic effect. All contaminants in the studied fish were either undetectable or present at very low levels when compared to the United States Food and Drug Administration (USFDA), Food and Agriculture Organization/World Health Organization (FAO/WHO), and European Union regulatory standards and yellowfin tuna would be one of the best options for people who frequently consume tuna fish to get sufficient EPA+DHA and essential elements.     

Histamine levels in commercially important fresh and processed fish of Oman with reference to international standards

Histamine was investigated in fresh (378), frozen (441), canned (290) and dried (24) fish samples of scombroid and non-scombroid species of Oman using a high performance liquid chromatography with a fluorescence detector. Of the 1133 fish samples tested, histamine was detected in 551 samples with a detection rate of about 41.8% among fresh fish, 61.0% of frozen fish, 78.9% of canned fish and 91.6% of dried fish samples and the mean histamine levels were 2.6, 5.8, 3.1 and 104 mg kg⁻¹, respectively. A total of 3.7% and 0.79% of the total samples exceeded the FDA and EU regulatory limits for histamine. Imported dried anchovies contained high histamine levels. The study confirms that post catching and commercialisation practices of seafood are adequate, warranting good quality fish and may not cause histamine risk to consumer in terms of human diet. While necessary monitoring may be done for imported dried fish products.