Atlantic and Pacific mackerel are caught in vast quantities globally. Understanding their capacity for suffering and improving capture and handling practices can reduce unnecessary pain.
Mackerel are fast-swimming, highly active pelagic fish that undergo extreme physiological stress during capture. Purse seine nets concentrate massive schools into progressively smaller volumes as the net is drawn closed, causing crushing pressure, oxygen depletion, and frantic escape behavior. Fish at the bottom of the pile suffer the weight of thousands of others. Transfer from net to vessel causes further physical trauma. Most mackerel are then live-chilled in ice slurry — a method that takes many minutes to cause insensibility in conscious fish and during which they experience cold shock and asphyxiation. The welfare challenges are enormous given the scale of capture. Brine chilling at very low temperatures combined with CO2 stunning represents an improvement available to some fisheries.