Puget Sound King Crab

Description:

The Puget Sound King Crab, also known as Lopholithodes mandtii, is an uncommon species of crab with distinct features that can be found on the West Coast of the United States; from Alaska to Central California. When they are born, juvenile Puget Sound King Crabs are primarily orange with some patches of red and purple. As they grow into adulthood, the L. mandtii form a more mixed shell color of red, orange, and purple. They can also grow to be an average size of 6 - 10 inches, with a carapace, or the dorsal side of the exoskeleton, growing upwards of 30 cm wide.[1] This makes the Puget Sound King Crab one of the largest crabs on the West Coast of the United States and yet it is still one of the hardest crab species to find. Another important characteristic of L. mandtii is the blunt, rounded bumps you will find all over them. Not only is this a necessary physiological trait that helps conceal the species in the subtidal, but the bumps also distinguish it from other closely related species, such as the Brown Box Crab, Lopholithodes foraminatus, which has spinelike pertrudements that are much sharper than the bumps on the Puget Sound King Crab.[4]

Distribution & Habitat:

As described before, L. mandtii is distributed along the Pacific Coast of the United States and has moved, as observed, from as far as Sitka, Alaska to Monterey, California. In these regions, the Puget Sound King Crab lives in close proximity to many other closely related species, such as the Alaskan King Crab.[6] In these areas, L. mandtii are known to be found anywhere between the subtidal to depths of about 140 m. They mostly take up rocky areas where they can easily maneuver around and hide themselves from physical and ecological factors such as strong currents and drag that could rip other organisms away.[5] Juvenile Puget Sound King Crabs are more likely to be found under rocks at low tide in order to avoid heat stress. This makes them easier to find compared to adult Puget Sound King Crabs which spend the majority of time at lower depths where there is a higher chance of catching prey. The exception to this is during the end of Winter/ beginning of Spring when they come up to shallow waters in order to mate and breed offspring.[2] As of recent, L. mandtii has become less common in the Puget Sound Straight region in Washington, USA. This is due to the shoreline modifications which negatively impact nearby habitats where various species, such as the Puget Sound King Crab, coexist.[5]

Community Impact & Status:

The Puget Sound King Crab is known to live in the subtidal regions along coasts which means it is part of a diverse community of marine life that interact with each other to create a dynamic environment. This species is in a position where it must catch prey and avoid predators in order to survive and thrive. L. mandtii is known to consume sea urchins and other invertebrates, such as starfish and sea cucumbers.[1] By controlling sea urchin populations, more seaweed and kelp will show up since there will be less invertebrates that consume those primary producers. In turn, the seaweeds and kelp conceal the Puget Sound King Crab from its predators in the sky, such as pelicans and other birds that consume marine life. This is an example of a changing cycle within this community because a disturbance or change any species population could alter the rest

of the community altogether. Unfortunate enough, L. mandtii is becoming more uncommon in the areas it used to thrive in. Part of this is due to increased use of fishing nets of different sizes which the crabs get caught in and brought up.[3] The Puget Sound King Crab has been put on the protected species list by the Washington Fish and Wildlife Department which means it is not advised to catch and collect this species.

References:

[1] Cowles, David, "Lopholithodes mandtii (Brandt, 1849)". Key to invertebrates found at or near the Walla Walla University Marine Station (Rosario) Fidalgo Island, Anacortes, WA, 2004.

[2] Dethier, Megan N., et al. Native shellfish in nearshore ecosystems of Puget Sound. No. TR-2006-04. WASHINGTON UNIV SEATTLE, 2006.

[3] Good, Thomas P., et al. "Derelict fishing nets in Puget Sound and the Northwest Straits: patterns and threats to marine fauna." Marine Pollution Bulletin 60.1 (2010): 39-50.

[4] Stevens, Bradley G., ed. King crabs of the world: biology and fisheries management. CRC Press, 2014.

[5] Toft, Jason D., et al. "Fish distribution, abundance, and behavior along city shoreline types in Puget Sound." North American Journal of Fisheries Management 27.2 (2007): 465-480.

[6] Zimmermann, Mark, C. Braxton Dew, and Beverly A. Malley. "History of Alaska red king crab, Paralithodes camtschaticus, bottom trawl surveys, 1940–61." Marine Fisheries Review 71.1 (2009): 1-22.