Do fattening process and biological parameters affect the accumulation of metals in Atlantic bluefin tuna?

Abstract

The objective of this study was to determine the current levels of heavy metals and trace elements in Atlantic bluefin tuna muscle tissues and how they are influenced by the fattening process and various life history parameters to ascertain whether the concentrations in muscle tissue exceed the maximum levels defined by the European Commission Decision and to evaluate the health risk posed by fish consumption. A total of 20 bluefin tuna reared in sea cages, ranging from 160 to 295 cm in length and from 80 to 540 kg in weight, were sampled from a bluefin tuna farm in the Ionian Sea. The condition factor K of each specimen was calculated and their age was estimated. Heavy metal and trace element (Hg, Zn, Fe and Cu) contents were determined in muscle tissue using cold vapour atomic absorption spectrometry and flame and graphite furnace atomic absorption spectrometry. The total Hg concentrations ranged from 0.28 to 1.28 mg kg^–1 w/w, Zn from 5.81 to 76.37 mg kg^–1 w/w, Fe from 12.14 to 39.58 mg kg^–1 w/w, and Cu from 0.36 to 0.94 mg kg^–1 w/w. Only 5% of the muscle samples of tuna contained Hg above the maximum level laid down by the European Commission Decision. Moreover, 15% of the muscle samples contained Zn above the maximum level, while Fe and Cu concentrations were within the acceptable tolerable guideline values. The reared bluefin tuna had lower concentrations of Hg than the wild ones from the Mediterranean Sea. Hg and Fe concentrations showed a positive relationship with size and age of bluefin tuna, whereas negative relationships were found for the concentrations of Zn and Cu. The estimated dietary intake values of the analysed metals were mostly below the derived guidelines.

Keywords:

• Thunnus thynnus
• heavy metal
• trace element
• accumulation
• aquaculture
• Mediterranean Sea

Acknowledgements

This study is part of a PhD thesis conducted at the Faculty of Biology, National and Kapodistrian University of Athens. The authors would like to express their most sincere thanks to Mr A. Tzoumas, General Director of Bluefin Tuna Hellas, for cooperation during the samplings; and Mr H. Mori as well as the Greek and Japanese commercial fishermen for the valuable help during the bluefin tuna measurements on board. Moreover, the authors thank the personnel of the Department of Environmental Chemistry, University of Athens – especially Vicky Paraskevopoulou – for assistance during the metal concentration measuring.