Trace elements in the dolphin fish (Coryphaena hippurus)

Abstract

Levels of the trace elements lead, cadmium, mercury and arsenic were determined in the dolphin fish (Coryphaena hippurus), a migratory fish that is widely consumed by the Maltese population. Various digestion and analytical techniques for the accurate determination of these elements in dolphin fish tissues were investigated. For the determination of lead, cadmium and mercury, the ideal analytical scheme identified in this project involved the microwave digestion of fish tissues. The most accurate results for arsenic determinations were achieved when dry ashing was utilized as the decomposition method prior to analysis by hydride generation atomic absorption spectrometry. The concentrations of these elements in muscle tissues of the 33 dolphin fish tissues analyzed ranged from <15 ng/g - 148 ng/g lead, <8 ng/g - 33 ng/g cadmium, 28 ng/g - 346 ng/g mercury and 0.53 mg/kg - 2.86 mg/kg arsenic. These values are much lower than the maximum permissible limits for human consumption. When compared to other predatory species, such as tuna and swordfish, from the Mediterranean Sea, the dolphin fish contains much lower concentrations of mercury in its muscle tissues. Analysis of different muscle and liver tissues of Coryphaena hippurus demonstrated that cadmium and arsenic are accumulated in higher concentrations in liver than in muscle, whilst no difference was found in lead concentrations between liver and muscle tissues. For mercury, significantly higher concentrations were found in muscle rather than liver for male specimens. The correlation between trace element concentrations and weight of dolphin fish indicate that certain elements (such as mercury) tend to accumulate with increasing weight of fish.