Upper thermal tolerance in red and blue king crab: sublethal and lethal effects

Red and blue king crab (Paralithodes camtschaticus and P. platypus) are both important fisheries species in Alaska. Despite the threat of climate change, the upper thermal tolerance of these species has been little studied. In this paper, we determine the lethal and sub-lethal thermal responses of year-0 juvenile red and blue king crab. Crab were exposed to a range of temperatures for 24 h to determine the lethal temperature at which mortality was 50% (LT50). Feeding rations were determined at sub-lethal temperatures for both species. Finally, crab were held for 45 days at sub-lethal temperatures and growth and long-term mortality rates were measured. The LT(50)s of red and blue king crab were 24.3 and 21.3 degrees C, respectively. Feeding ration peaked between 12 and 17 degrees C for red king crab and between 5 and 10 degrees C for blue king crab. The growth rate of red king crab decreased at temperatures above 12 degrees C, while blue king crab exhibited very low growth rates at temperatures 12 degrees C and above. Increased mortality in the 45-day experiment occurred for red king crab at 20 degrees C and blue king crab at 17 degrees C. This study suggests that, within their current distribution, the juveniles of both species could withstand warming of several degrees and not be thermally stressed; however, more research into the effect of increased temperature variability and other response variables, such as resting and active respiration, is needed. In addition, increased temperature could affect other life-history stages differently or have indirect effects, such as altered species interactions and food availability.