Pumping of mackerel (Scomber scombrus) onboard purse seiners, the effect on mortality, catch damage and fillet quality

Differences in the mortality, catch damage, and fillet quality of mackerel pumped either from the seine directly onboard the catching vessel or transferred at sea to a secondary vessel were explored. Three studies were performed on commercial vessels, both purse seiners and coastal seiners, during the catching season in September and October 2012–2014. Most of the fish died after 20 to 60 min due to the duration of the crowding time. There was a significantly higher survival rate for the fish that were pumped to the main vessel due to shorter crowding time compared to the fish that were pumped to the secondary vessel, with an average survival rate of 53.4% ​​versus 23.9% The mackerel caught with the secondary vessel in 2014 had a significantly higher proportion of catch damage and discolorations compared to the fish caught with the main purse seine in 2014, and coastal vessels in 2012 and 2013. For the experiment in 2014, a sensor fish was developed with the purpose of registering acceleration forces (g-forces) during pumping. The results from the sensor fish revealed that more strain/g-forces (29%) were exerted on the fish pumped to the secondary vessel as compared with the main vessel. This is likely to be the result of several factors: (a) the pump speed was higher (30%), (b) more fish were processed, and (c) the tubing system extension of 50 m created a “rollercoaster” course for the fish. The quality of the fillets was good overall, but with some differences in gaping scores between the main and secondary vessels after storage onboard.