Abstract
Blue swimming crab (Portunus pelagicus) is widely found in Indian and Pacific Oceans, and many other sea areas, including the Arabian Gulf. Like the other benthic
crustaceans, Portunus pelagicus accumulates different trace metal ions among their tissues. Blue Swimming Crab (BSC) is popular seafood in Bahrain; therefore, it is
important to study its trace metal ions content.
This study determined the levels of six trace metal ions in the tissues of male and female BSC collected from four marine sites within the territorial waters of Bahrain
namely, Ra's Al M'ttalah (west), Marwada (north), Askar (east) and Tubli Bay.
The study was divided into two parts; in the first part, the levels of Zn2+, Cu2+, Cr3+, Ni2+Pb2+ and Cd2+ were determined in both white meat (muscles of the legs and claws) and brown meat (digestive system) of BSC on the dry weight basis. For all stations, male and female composite samples of white and brown meat were prepared from 15 crabs.
Based on first part results, three metal ions (Zn2+, Cu2+ and Cd2+) were also determined in individual males and females BSC samples on wet weight basis. White and brown meat of ten male and ten female crabs from each site were analyzed.
The concentrations of Zn2+, Cu2+, Cr3+, Ni2+ and Cd2+ were in the range of 174.6 – 300.4, 33.3 – 325.7, 0.025 – 0.25, 0.11 – 3.03 and <0.02 – 10.3 mg/kg dry weight,
respectively. While Pb2+ was below method quantification limit (<0.2 mg/kg).
Generally, the concentrations of trace metal ions were in the following order Zn2+ >
Cu2+ > Cd2+ > Ni2+ > Cr3+
. The study revealed that BSC tends to accumulate Cu2+ and Cd2+ in brown meat more than in white meat, while no significant difference was observed between Zn2+ concentrations in the two tissues. Female crabs were found to accumulate Zn2+ more than male crabs in both white and brown meats, as well as Cu2+
in the white meat. Crabs from Ra's Al M'ttalah had higher concentrations of Cu2+ and Cd2+ in their brown meat compared to crabs from other sites while crabs from Marwada had higher concentration of Zn2+ in both white and brown meats compared to crabs from other sites.
In view of study results, Cd2+ and Pb2+ levels in white BSC meat are considered safe for human consumption according to both Bahrain's standards (GSO 1922/2009) and European standards (EU No 420/2011). However, it is recommended to refrain from eating BSC brown meat as it tends to have high level of Cd2+.