King crab

red-king-crab_indic

Paralithodes camtschatica

Originating from the Sea of Okhotsk in the Camchatca region of eastern Russia, and also native to the Bering Sea, the red king crab (Paralithodes camtschatica) was introduced to parts of the Russian waters of the Barents Sea in the 1960’s. In the mid 1970’s, individual specimens started to appear as bycatch on both sides of the shared Russian/Norwegian border. Since that time, bycatch numbers have increased significantly in that region.

The king crab is a valuable food source and as the world’s largest edible crab, it is the most commercially important of all crabs. Whilst a number of studies have examined the optimum harvesting strategies for the species, very little has been done to understand the potential ecological impact that the species is likely to have in non-native waters.

The crab’s diet appears to include a wide range of organisms, especially polychaetes worms, small bivalves such as clams and echinoderms like sea urchins and starfish. It consumes large quantities of food relative to its body size; creating concern that serious depletion of some benthic (bottom dwelling) species may occur where there are high concentrations of crabs in a limited area. The crab may well be a significant food competitor of bottom-feeding fishes. Whilst they do not compete directly with any other species, as they are generalist predators and voracious feeders, they can alter the balance of the ecosystem.

The red king crab population is dramatically rising in numbers and spreading in distribution. The Barents Sea population has increased six-fold since 1995, with an estimated 12 million members of the species now resident. The crabs can be found at depths ranging from the shoreline down to 400 metres, depending on size, age and season.

One of the largest crabs, they can live for up to 25 years in the Arctic and can grow up to 1.5m, weighing up to 8-10 kg. King crabs are unique in that they have only 6 legs while most crabs have 8. When alive, it is actually dark burgundy in colour.

There are two other species of king crab that can be found in the region. The blue king crab (Paralithodes platypus) is actually brown when alive, with royal blue highlights. It has more spines on the shell.

The shell of the smaller brown or golden king crab (Lithodes aequispina) is a uniform light brown to golden colour. These last two species should not be recorded in the Global Dive Log, but please feel free to note any that you see in your dive log, so that other earthdivers can share in your experience.