Malachite green residues in farmed fish in Croatia

Malachite green concentrations were determined in muscle tissues samples of 42 carp (Cyprinus carpio) and 30 rainbow trout (Oncorhynchus mykiss) collected from fish farms in Croatia from 2009 to 2011. Concentrations were determined using the immunoassay method, validated according to the criteria of Commission Decision 2002/657/EC. The method performance is appropriate for the detection of malachite green, due to the obtained CCβ (0.68 μg kg−1) and LOD (0.31 μg kg−1) values that were below the MRPL level of 2 μg kg−1. Malachite green levels above the limit of detection of the method were determined in 18.1% of samples tested. The mean malachite green level (0.231 μg kg−1) of samples tested was lower than the determined limit of detection of the method. Concentrations ranged from 0.1 to 0.3 μg kg−1 in 68.1% of all fish samples. The measured concentrations exceeded 1 μg kg−1 in only two samples and the highest concentration (1.07 μg kg−1) was measured in rainbow trout muscle. Since this study is limited to malachite green residues, further investigation is required for determination of its metabolite, leucomalachite green. Additional surveillance programmes with a larger number of fish muscle samples should be carried out to improve the risk assessment.