Red king crabs (Paralithodes camtschaticus) are large marine crustaceans found in the cold North Pacific, from British Columbia to the Bering Sea and Kamchatka Peninsula. Males can reach 24 pounds with a five-foot leg span. Juveniles inhabit shallower habitats like shell hash and algae beds, while adults move to deeper continental shelf waters.
Key Food Sources
Red king crabs exhibit an omnivorous and opportunistic feeding strategy, consuming a wide array of organisms available in their benthic environment. Their diet includes various invertebrates such as worms, clams, mussels, barnacles, and other crustaceans. They also consume echinoderms like sea stars, brittle stars, and sand dollars. Algae, detritus, and even fish parts contribute to their diverse diet, especially for larger individuals.
Feeding Behaviors
Red king crabs actively forage on the seafloor, employing various methods to obtain food. They are known to scavenge on dead or decaying organic matter. Beyond scavenging, they also prey on live organisms, using their specialized claws to manipulate and crush food items. The larger, heavy-duty claw is particularly effective for crushing shells, while the smaller claw assists in more delicate handling of food. Their sensory abilities, including chemoreception, help them locate potential food sources in their environment.
Factors Influencing Their Diet
Several factors contribute to the variations observed in the diet of red king crabs. The life stage of the crab significantly influences what it consumes; larval stages, for instance, feed on phytoplankton and zooplankton in the water column. As they mature, their diet shifts to benthic organisms, with smaller crabs eating algae, small worms, and clams, while larger crabs consume a broader range of items. Seasonal availability of prey and geographical location also play a role, as the abundance of specific food items can change with seasons and across different regions. The specific benthic environment, such as soft sediments versus rocky areas, can determine the types of organisms accessible to the crabs.
Role in the Food Web
Red king crabs occupy a significant position within their marine food web as both predators and scavengers. Their feeding habits contribute to nutrient cycling on the seafloor by consuming detritus and various benthic invertebrates. As generalist predators, they exert top-down effects on populations of long-lived benthic invertebrates, including gastropods, asteroids, and sea urchins. This predation can influence the structure and composition of benthic communities. While they are consumers of many organisms, larger red king crabs have few predators themselves, primarily being preyed upon when their shells are soft after molting.