AFSC/RACE/SAP/Long: Data from: Upper thermal tolerance in red and blue king crab: Sublethal and lethal effects

Laboratory study in Kodiak Alaska

Note: Dataset migrated by Dan Woodrich (AFSC data management coordinator) on 12/16/2021. Contact: Daniel.woodrich@noaa.gov

Initially, seven different temperatures were tested for both species: 14, 16, 18, 20, 22, 24, 26°C. As the trials were performed, we added an additional temperature treatment for each species at around the estimated LT50 ( temperature that causes 50% mortality): 21°C for blue king crab and 25°C for red king crab. The trials were run in a random order. For the seven temperatures tested in common among the species, both species were tested simultaneously. For each trial, 14 year-0 red and blue king crab were haphazardly assigned to each treatment. At the beginning of the experiments, all the tanks were at ambient temperature (i.e., the same temperature the crabs were being held at). The temperature in each tank was then increased gradually to the experimental temperature over 4 hours. The crabs were left at the temperature for 24 h after which they were checked for activity by gently prodding them with a dissecting needle and observing whether they responded by moving away from the needle. They were then checked to see if they were alive.

In this experiment, the effects of temperature on feeding ration were determined for red and blue king crabs. Temperatures tested included 11, 13, 15, 17, 20, and 23°C for red king crab and 4, 6, 9, 11, 13, 15, 17, and 20°C for blue king crab.Year-1 blue king crab and year-0 red king crab were used. In each trial 5 (blue king crab) or 7 (red king crab) crab were massed and then introduced into individual holding cells. The temperature was slowly adjusted to the treatment temperature over 4 h. Crab were allowed to rest for 24h to acclimate them to the temperature and to standardize hunger levels. Then crab were fed small pieces of massed squid mantle and allowed to feed for 24h. At the same time, pieces of food were also placed in three control cells without crab. After this, the remaining food was removed and massed. Daily feeding ration, expressed as a percentage of the crab’s mass, was calculated for each crab and corrected for the change of mass of the food in the control cells assuming a minimum feeding ration of 0%. In a few cases, crab molted during the trial or ate all the food and the data from these crab was excluded from analysis.

To determine how temperature affects growth and long-term survival in year-0 crabs we performed 45 day experiments. Red king crab were tested at 12, 15, and 20°C and blue king crab at 12, 15, and 17°C. Twelve crabs per species per treatment were haphazardly selected. Crabs had their carapace width measured and were introduced into individual holding cells. The temperature was slowly adjusted to the treatment temperature over 4 h. Crabs were checked daily for molting or mortality and were fed to excess. After the end of the experiment each crab had their carapace width measured a second time.