Efficacies of cooking and depuration for reducing current-use pesticide residues in wildcaught giant mud crabs (Scylla serrata)

Benjamin C T Gray^1*Curtis Champion²Matt Broadhurst^2,3Melinda Ann Coleman²Kirsten Benkendorff¹

• ¹National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, Australia
• ²Fisheries Research, NSW Department of Primary Industries and Regional Development, Coffs Harbour, Australia
• ³School of the Environment, The University of Queensland, Brisbane, Australia

Pesticides can be transported into estuaries via spray drift, ground water contamination and surface runoff. Increasing climatic variability and global pesticide use are likely to increase the exposure of harvested estuarine species, and therefore seafood consumers, to agrichemicals. Post-harvest processing strategies present opportunities to reduce pesticide residues in seafood and so mitigate consumer health risks. We evaluated the efficacies of thermal processing (cooking) and depuration (holding individuals in clean flow-through seawater) for reducing pesticide residues in wild-caught giant mud crab (Scylla serrata) edible tissues (flesh and brown meat (i.e. hepatopancreas and gonads)). Pesticide residues were detected in 82% of assessed crabs, with five analytes quantified (cyprodinil, diuron, imidacloprid, propargite and triazophos). Correlative analyses revealed cooking at ~82°C for 2 min 100-g -1 body mass reduced all pesticide concentrations (and the total residues) in both tissues by 7-99%-except for cyprodinil (51% increase). Imidacloprid residues in crab flesh were reduced (by 81%) after six days of depuration, with complete elimination after 12 days.While a human health-risk assessment identified that the concentrations of pesticide residues in crab tissues posed no negative health effects to seafood consumers, the data support postharvest processing methods for mitigating consumer exposure. Our study highlights the need for ongoing pesticide surveillance of Australian seafood. Food safety regulation should consider establishing maximum residue limits for seafood, with consideration of consumption preferences.