Physiological responses to live air transport of red king crab (Paralithodes camtschaticus)

•Red king crabs were air transported live, mimicking commercial practices.•Crab haemolymph was collected before and after the transportation.•Cl−, Na+, lactate and total protein increased in the transported crabs.•Free Ala, Arg, Thr, Val and Tau were elevated in the transported crabs.•Crabs exhibited the typical physiological responses associated to hypoxia stress. Live transport of red king crab from the fishing grounds to the market is an activity that is increasing and the future sustainability of this practice depends on maintaining optimal animal welfare during transport. The current study evaluated the physiological response of red king crab (Paralithodes camtschaticus) to live air transport, mimicking current commercial practices. Specifically, this study assessed stress and osmoregulatory haemolymph metabolite variation, together with free amino acids (FAAs) pool variation in the haemolymph of red king crab. Forty male crabs (2136 ± 800 g) were caught in the North Cape area in the Barents Sea during April 2019. They were transported by the fishing boat directly to a land-based live holding facility in Honningsvårg, Norway where they were held for < 10 days. They were then divided in two groups: i) the first group of 20 crabs underwent immediate haemolymph sampling, and ii) the second group of 20 crabs was divided in subgroups of 5 crabs, placed in a standard air freight Styrofoam boxes with freezer packs and transported by road and air to the Nofima facility, in Tromsø, Norway. The time from the packing until when the haemolymph sampling occurred was 20 h. All samples of haemolymph were taken from the coxa membrane of the third right side walking leg and were analysed for sodium (Na+), chloride (Cl−), carbon dioxide (CO2), lactate, total protein, and FAAs. The survival of the transported crabs was 100 %, and after transport the measured indicators showed a significantly positive (lactate and total protein) or a negative (Na+, Cl−) variation in relation to the air transport. From the measured FAAs, five, Alanine (Ala), Arginine (Arg), Threonine (Thr), Valine (Val) and Taurine (Tau), were significantly higher for the group after transport when compared to the group before transport. No FAAs were significantly lower as a result of transport. In conclusion, it was apparent that red king crabs exposed to air during a 20 -h transport period exhibited the typical physiological responses associated to hypoxia stress. Moreover, in this study we report for t