These striking bluish-purple crabs are not nearly as famous or as widespread as their red cousins. Unlike the red king crab, blue king crabs only breed once every couple of years. Males may grow up to 18 lbs (8 kg). Scientists are still researching the reasons for the blue king crab’s low numbers. One thought is that the blue king crabs’ preference for cold water may reduce their appetite or result in food scarcity. The blue king crab will subsequently take in less energy, leaving less to support breeding.
Along with humans, the blue king crab’s predators include fish, other king crabs, and octopuses.