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The Thermal Tolerance of Red and Blue King Crabs

Paper Reviewed
Long, W.C. and Daly, B. 2017. Upper thermal tolerance in red and blue king crab: sublethal and lethal effects. Marine Biology 164: 162, DOI: 10.1007/s00227-017-3190-1.

Providing the rationale for their study, Long and Daly (2017) write that "knowing the range of temperatures over which an animal can survive, grow, and reproduce is key to understanding and predicting that animal's distribution and population dynamics." This is especially important in light of model predictions of a 3°C increase in sea surface temperature by 2200 in response to rising atmospheric CO2 concentrations (Bopp et al., 2013).

The red (Paralithodes camtschaticus) and blue (Paralithodes platypus) king crabs are two important fisheries species found in Alaskan waters. To date, however, little research has been conducted on how these two crabs might respond to projected changes in climate, particularly during the important juvenile stage. Therefore, Long and Daly set out to examine the thermal tolerances of these two species. The specific experimental design for their analysis involved subjecting year-0 juveniles to eight different temperature treatments between 14 and 26 °C. Temperatures in each treatment were gradually increased to the experimental temperature over a four-hour period. Thereafter, the crabs were left in their corresponding temperature treatments for 24 hours, after which they were examined to see if they were alive.

Results of the analysis revealed that the lethal temperature at which 50 percent mortality occurred was 24.0 °C for the red king crab and 21.3 °C for the blue king crab. In commenting on their findings, Long and Daly note that these mortality temperatures are well above those that occur throughout each crab's range, suggesting that "juveniles will be resistant to near-future levels of climate changes." Additionally, they write that "a 2-3 °C increase in temperature may result in seasonal sea-surface temperatures slightly higher than the pejus temperature in the southernmost populations, but well within the thermal tolerance of both species; and the gradual rate of change will give time for evolutionary adaptation as well." In fact, "increased temperatures may actually be a net benefit as higher temperatures could lead to a higher maximum potential growth rate."

Thus, it would appear that a little ocean warming would be beneficial to these two key Alaskan fisheries species.

Bopp, L., Resplandy, L., Orr, J.C., Doney, S.C., Dunne, J.P., Gehlen, M., Halloran, P., Heinze, C., Ilyina, T. and Seferian, R. 2013. Multiple stressors of ocean ecosystems in the 21st century: projections with CMIP5 models. Biogeosciences 10: 6225-6245.

Posted 21 November 2017