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King Crab in the Caribbean

 

We were diving a wall at about 80 feet off the coast of Roatan, Bay Islands, Honduras, when my new dive buddy signaled me to drop another 10 feet, swim under a ledge, and stick my head into a large hole behind the ledge. 

Once I wriggled into the hole I found myself in a very small, dark cave so I unclipped a dive light and eased it into the hole.  At first I saw nothing but a scum-covered reddish rock until…one really large claw bumped my mask and I realized the red rock was a rather large crab with a claw seemingly the size of Manhattan.

Fortunately, the crab did not react aggressively to the invasion of his space for he could have easily caused serious damage to my face as well as to the budding friendship with my new dive mate.  I watched him for several minutes until I felt a tug on my fin and was yanked out of the hole by my then-very-concerned mate who had decided I was suffering from nitrogen narcosis and was incapable of extricating myself from the hole.  And this was only our first day of diving together…with many more adventurous days to come.

Since that crab and his kin are a rather elusive nocturnal lot, I didn’t see another one until a night dive on a wreck.  The ship sat on its starboard side with the keel a few feet off the seabed creating an overhang.  I took my dive students down to investigate whatever might be lurking there and to my delight; there were several of those large reddish crabs in residence.

Mithrax Spinossisimus, aka Caribbean King Crab, Channel Crab, or Channel Clinging Crab, belongs to the family Majidae in which there are approximately 700 species.  Because many of the species have very long legs, they are also called Spider Crabs.  Sizes range from minute to the Japanese King Crab that can have a 14 foot leg span.

They are crustaceans, having an exoskeleton, external skeleton, rather than internal.  The family Majidae is characterized by a carapace, dorsal section of the exoskeleton, which is short, wide, and somewhat triangular.  In addition, the exoskeleton is covered in rough bumps and bristles to which the crabs may attach algae and, in the case of the Decorator Crab, anemones and small shellfish that serve as camouflage.   

The Caribbean King Crab is found from North Carolina to Venezuela.  “Modern crabs” have been helping to keep the world’s oceans clean for about 200 million years with a more primitive version dating back almost 400 million years. 

Surprisingly little is known about the Caribbean King Crab and what information is available comes mainly from research into the feasibility of commercially raising the crab; perhaps, due to the deeper depths at which the elusive crabs are found. Based on the crabs I have observed in the wild, the Caribbean King Crab appears to be the same general size as the much more studied Alaskan King Crab.
 
Like all true crabs, the Caribbean King Crab has five pairs of legs, threer pair for walking, one pair called swimming legs, and the fifth pair known as chelipeds, aka pincers or claws.  The Caribbean King Crab’s chelipeds are spoon shaped, designed for scraping algae, its main food source, from rocks and corals

And, like all crustaceans, the crabs must periodically shed (molt) their hard exoskeletons since the exoskeleton cannot expand to accommodate their growing bodies.  Once fully mature, the Caribbean King Crab’s underside has a hardened, hinged flap protecting the reproductive organs. 

The females carry hundreds of eggs under the hinged flap along with the stored sperm until its time to spawn.  Shortly after spawning the eggs hatch with the larvae are known as zoea.  Unlike other crab species, the zoea of the Caribbean King Crab mature rather rapidly to the next stage known as megalopa where upon they begin to resemble tiny crabs and settle to the bottom to begin feeding upon algae and start the long process of molting until they become fully mature; a process than can take up to 5 years.  However, during research studies, marketable size was obtained in about 18 months.

Back in the 1980’s scientists with the Food and Agriculture Organization of the United Nations, the Smithsonian Institute, U.S. Agency for International Development, the Peace Corps, and the French government studied the possibility of farming the Caribbean King Crab in the Caribbean.  With fishermen finding it more difficult to make a living on over fished reefs, aquaculture appeared to offer a solution. 

Walter Adey of the Smithsonian, one of the first to successfully raise the crab in conjunction with research on algae farming stated "It tastes as good as Alaskan King Crab.”  Unfortunately, it appears that none of the experimental ventures in commercially raising the crab were successful.

A privately funded venture in the Turks and Caicos failed when the investor went broke.  The French scientists who proposed aqua-culturing the crab on Carriacou offered not only technical support but also financial, citing the relatively low start-up costs, low energy consumption, closeness to the North American market, and ease of producing the algae the crab feed upon.  However, the project never seems to have gotten off the ground due to lack of local government interest, with priorities focused on the tourism trade instead.  Proposed crab rearing operations on Antigua and other Caribbean locations seem also to have fallen by the wayside with some notations as to the lack of local interest.

Next month….my dive buddy sends me under a mushroom shaped rock from whence I exited very quickly on my own with my mask askew.

After 30 years as a wild and domestic animal rescuer, rehabber, and educator in the states, Becky Dayhuff-Bauer became a scuba instructor and award-winning journalist covering the marine environment in the Caribbean.  She is a contributing photographer to NOAA.

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