Optimum conditions using manganese as a shell marker for abalone age validation studies

Abstract

Blacklip abalone, Haliotis rubra (L.), were immersed for 48 to 144 hours in buckets containing sea water to which MnCl2.4H2O was added at concentrations ranging from 9.5 to 1890 mg L-l, in order to determine the optimum concentrations for marking. Manganese concentrations above 945 mg L-1 over the immersion period were lethal to abalone. Cathodoluminescence microscopy was used to detect manganese mineralised within shell layers in situ. Although the average length and width of manganese carbonate marks at the outer growing margin of the abalone shell increased with higher concentrations, marks in the shell area under the spire appeared to be maximal at intermediate concentrations. Better mar..