Magnesium chloride pre-treatment reduces transport stress in the green-lipped mussel, Perna canaliculus: an integrated physiological, behavioural and metabolomic assessment

The New Zealand green-lipped mussel, Perna canaliculus , is a key aquaculture species, and improving live transport performance is vital for quality and supply. Mussels pre-treated with magnesium chloride (MgCl 2 ), ambient 14 °C, or chilled 4 °C seawater were assessed after a 3-day simulated out-of-water live transport at 8 °C and recovery in seawater (+1 h, 1 day, 14 days) for gill and adductor metabolomics, haemolymph biochemistry (pH, antioxidant capacity and osmolality), heart rate (HR) and relative gaping magnitude (RGM), allowing comparison of treatment-specific responses. During the live transport simulation, mussels pre-treated at 14 °C showed elevated HR, whereas 4 °C- and MgCl 2 -treated mussels had lower HR on Day 1. By Day 3, HR was low (~1 bpm) and did not differ among treatments. Compared to 14 °C- and 4 °C-pre-treated mussels, MgCl 2 -pre-treated mussels showed higher RGM and 1.6–2.3-fold lower anaerobic biomarkers (e.g., succinate, alanine and strombine), indicating reduced metabolic stress and minimal anaerobic activation. After 1-h recovery, there was a significant difference between metabolic profiles of mussels from different pre-treatment groups, which was largely driven by varying levels of metabolites for anaerobic energy metabolism (e.g., succinate and strombine) for cellular stress responses and during early stages of recovery. MgCl 2 -treated mussels showed increased anaerobic markers, but lower than the other groups, suggesting less energy was needed to recover from transport-induced stress. After 1-day recovery, metabolic profiles of all groups resembled control mussels, indicating successful recovery. Overall, MgCl 2 pre-treatment of mussels provided the most effective mitigation of transport stress and supported faster recovery, highlighting its potential for improving long-distance live mussel transport. • Study assessed MgCl 2 , 14 °C and 4 °C to reduce mussel live transport stress. • Chilled mussels showed higher anaerobic stress biomarkers than MgCl 2 . • MgCl 2 has promise as pre-treatment to reduce stress for mussel live transport. • Mussels followed live transport recovered after 1-day re-immersion in seawater. • MgCl 2 pre-treated mussels show recovery anaerobic biomarkers similar to controls.