Heavy metal bioaccumulation and Fulton’s K condition indices in Scylla serrata (Forskål) in relation to sex

Abstract

This article discusses the temporal variation and stress of heavy metal accumulation in Scylla serrata (Forskal) with reference to sexes. Cd and Sn were undetected (i.e., below the method detection limits of 0.001 Cd mg/kg wet weight and 0.005 Sn mg/kg) in both sexes. However, Scylla serrata (Forskal) consistently exhibited high accumulation of As, Pb, Hg and Zn. Zn was the most abundant metal in both sexes. (Average Zn content in males and females was around 40.76 ± 2.51 and 45.10 ± 2.24 mg/kg wet weight, respectively.) Pb and Hg levels exceeded EU and Sri Lankan admissible limits on many occasions (0.02 Pb mg/kg wet weight and 0.5 Hg mg/kg wet weight). Bioconcentration factors (BCFs) of As and Zn from the water > 1 in both sexes indicating effective direct uptake from the water. However, temporal variation of Zn and Hg and the interaction between temporal variation of these metals and the two sexes were insignificant (P > 0.05). Nevertheless, temporal variation of Pb (P < 0.008) and As (P < 0.05) and the interaction between temporal variation and gender were significant with females exhibiting higher BCFs (As P = 0.002, and Pb P = 0.003). However, there was no statistical significance (P = 0.355) in the Fulton’s K condition index in relation to gender despite females exhibiting higher As and Pb levels. (Highest As and Pb levels in females were around 5.9 As mg/kg wet weight and 0.12 Pb mg/kg wet weight.) Therefore, Fulton’s K condition index is not a reliable indicator regarding stress in crabs due to heavy metal accumulation.