Menippe mercenaria and its closely related and co-occurring species, Menippe adina, have recently been the subject of much research on hybrid zones and evolutionary speciation. M. mercenaria is sympatic with M. mercenaria along the Gulf Coast of Florida and forms allopatic populations along to the Gulf Coast, all the way to Mexico. These recent studies have provided conflicting evidence as to when the two species were isolated, and what effects recent contact has had on the development of each species.
The stone crab's primary method of communication is visual signaling. Before engaging in an intraspecies confrontation, a stone crab will openly display its massive claws. The larger the claws, the more likely that stone crab will be able to claim the local ideal breeding habitat.
Communication Channels: visual
Menippe mercenaria is not endangered, but it is protected by United States Code Title 16, ch. 38, and the Magnuson-Stevens Fishery Conservation and Management Act. These laws recognize the need to regulate trapping of the stone crab, and establish that only one claw may be removed per stone crab (none if it is an ovigerous female) if it is at least 6.99 cm (2 and 3/4") from the first joint to the tip of the lower immovable finger.
US Federal List: no special status
CITES: no special status
Upon hatching, Menippe mercenaria develops through five zoeal stages, which collectively make up the larval stage. These stages lasts between 14-27 days and are strongly dependent upon water temperature. The stone crab then develops into a post-larval stage that lasts between 1 and 2 weeks. During the larval and post-larval stages the stone crabs live among the zooplankton in nearshore waters. From the post-juvenile stage to when the carapace of the young crab develops to a width of 10 mm, the stone crab is considered to be a post-settlement juvenile. At this time they move away from the zooplankton into areas densely populated with other juvenile stone crabs. These places are usually seagrass beds or areas around emergent live rocks. It will then take the stone crab around 12 months to become a late juvenile, which is described as having a carapace width greater than 10 mm but less than 35 mm across. With a carapace width of 35 mm, the stone crab enters into adulthood.
Adult M. mercenaria feed primarily on hard shelled molluscs, some of which are also fished for human consumption. The stone crab does not play a significant role in reducing these populations, but they are capable of adversly affecting the industry.
Between 3 and 3.5 million pounds of Menippe mercenaria claws are harvested annually in Florida alone. This occupation employs around 4,000 crabbers in Florida, as well as many restaurant employees along the eastern sea-board. Federal law mandates that only one claw per crab be removed (it will grow back in 1-2 years), and that the claw must be at least 6.99 cm (2 and 3/4") from the first joint to the tip of the lower immovable finger. Overall, the stone crab industry generates 12-15 million dollars from Florida to North Carolina.
Positive Impacts: food
The larvae of the stone crab contribute to the nearshore zooplankton population that is critical to feeding larger fish. Federal law protects the stone crab from over-harvesting by man, and there has not been a reported disturbance in the nearshore marine ecosystem since this law was enacted.
As Menippe mercenaria grows and develops, its food habits change. The larvae and pre-juvenile stone crabs are opportunistic carnivores that feed on smaller zooplankton. The juvenile and adult stone crabs are still opportunistic carnivores, but feed on animals that are larger than the zooplankton. Utilizing their massive and powerful claws, adult stone crabs feed on acorn barnacles, hard shelled clams, scallops, and conch.
Animal Foods: mollusks; aquatic or marine worms; aquatic crustaceans; echinoderms; other marine invertebrates; zooplankton
Primary Diet: carnivore (Eats non-insect arthropods, Molluscivore ); planktivore
The stone crab, Menippe mercenaria, can be found just below the low tide line from the Atlanic coast of North Carolina to the Gulf coast of Florida.
Biogeographic Regions: atlantic ocean (Native )
Adult Menippe mercenaria generally inhabit sub-tidal regions; they burrow under emergent hard substrate or in seagrass beds. Juvenile stone crabs are found nearshore in marine waters on seagrass beds, or around emergent live rocks in highly dense populations. Some juveniles have been caught in deep channels near the Florida coast. The stone crab larvae travel with the zooplankton, upon which they feed, in nearshore marine environments.
Range depth: <1 to 70 m.
Habitat Regions: saltwater or marine
Aquatic Biomes: coastal
Other Habitat Features: intertidal or littoral
From egg to death, male Menippe mercenaria live for approximately 6 years, while the females live to be approximately 7 years old.
Typical lifespan
Status: wild: 6 to 7 years.
Average lifespan
Status: wild: 6-7 years.
Stone crabs have exoskeletons and have a brown and black speckled carapace that is oval, smooth, and convex. The carapace averages 130 mm across in adult females and 145 mm across in adult males. Adult Florida stone crabs have a trunk composed of 14 segments, and 5 pairs of stout walking legs, which have reddish and yellow bands and distal hairs. The first eight segments compose the thorax, and the remaining six segments compose the abdomen. The first set of walking legs develop into an asymmetrical pair of heavy chelipeds that typically make-up 60% of the animal's entire body weight and possess a crushing pressure of 14,000 pounds per square inch.
Juveniles are a dark purplish blue. Younger juveniles have a white spot on the carpus, which is the middle segment of the endopod, or limb.
Average length: 0.079 m.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger
The most obvious anti-predator adaptation is the development of massive chelipeds that are capable of exerting 14,000 pounds per square inch of pressure. These claws keep the number of adult stone crab predators to a minimum. The general consensus among experts in the study of Menippe mercenaria believe the low number of natural predators is probably due to the hard exoskeleton of the stone crab, which allows it to survive long enough to pinch and gash the predator's gastrointestinal lining. One species that seems completely unconcerned with the massive chelipeds of the stone crab is the octopus, which is the primary natural predator of the stone crab. Juvenile stone crabs are also depredated by large fish.
Known Predators:
Most female Menippe mercenaria sexually mature around two years old, and are most likely to breed between the spring and fall. The female carries her eggs in a sac-like mass containing 160,000 to 1,000,000 eggs. Optimum water temperature for ovarian development is around 28 deg C. Menippe mercenaria breeds year-round, although the peak mating season is from August to September in southern Florida. Males may mate with recently molted females.
Breeding season: Year round
Range number of offspring: 160000 to 1000000.
Range gestation period: 9 to 14 days.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); oviparous
The female carries her eggs in a sac-like mass containing 160,000 to 1,000,000 eggs until they hatch.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female)
The Florida stone crab (Menippe mercenaria) is a crab found in the western North Atlantic, from Connecticut to Colombia, including Texas, the Gulf of Mexico, Belize, Mexico Jamaica, Cuba, The Bahamas, and the East Coast of the United States. The crab can also be found in and around the salt marshes of South Carolina and Georgia. It is widely caught for food. The closely related species Menippe adina (gulf stone crab) is sometimes considered a subspecies – they can interbreed, forming hybrids – and they are treated as one species for commercial fishing, with their ranges partly overlapping. The two species are believed to have diverged approximately 3 million years ago.[1]
The stone crab's carapace is 125 to 165 mm (5 to 6+1⁄2 in) wide.[2] They are brownish red with gray spots and a tan underside, and have large and unequally sized chelae (claws) with black tips.[3] In addition to the usual sexual dimorphism exhibited by crabs, the female Florida stone crabs have a larger carapace than males of a similar age, and males generally have larger chelae than females.[3]
Florida stone crabs prefer to feed on oysters and other small mollusks, polychaete worms, and other crustaceans. They will also occasionally eat seagrass and carrion. Predators that feed on stone crabs include horse conch, grouper, sea turtles, cobia, and octopuses.[4]
Stone crabs can be found in 15–90 cm (1⁄2–3 ft) deep holes near dock pilings in water 30–150 cm (1–5 ft) deep. Oftentimes the hole will have shells around the opening; the crab uses the shell as a digging tool for the hole construction.
Females reach sexual maturity at about two years of age.[3] Their long spawning season lasts all spring and summer, during which time females produce up to a million eggs.[3] The larvae go through six stages in about four weeks before emerging as juvenile crabs. Their lifespan is seven to eight years.[3] The male Florida stone crab must wait for the female to molt her exoskeleton before they can mate.[3] After mating, the male will stay to help protect the female for several hours to several days. The female will spawn four to six times each season.
The Florida stone crab loses its limbs easily to escape from predators or tight spaces, but their limbs will grow back. When a claw is broken such that the diaphragm at the body/claw joint is left intact, the wound will quickly heal itself and very little blood is lost. If, however, the claw is broken in the wrong place, more blood is lost and the crab's chances of survival are much lower. Each time the crab molts, the new claw grows larger.
The crab only molts at night or in night-like conditions due to the crab being extremely vulnerable to predators without the protection of its shell. If the crab is becoming too large for its shell and the sun is up, the crab releases a hormone from a gland located on one of its eye stalks called the x-organ. This hormone prevents the crab from molting from its shell until it finds a safe place to molt or it has become dark enough outside to molt in safety.
The Florida stone crab is usually fished near jetties, oyster reefs or other rocky areas, just as for blue crabs. The bodies of these crabs are relatively small and so are rarely eaten, but the claws (chelae), which are large and strong enough to break an oyster's shell, are considered a delicacy. Harvesting is accomplished by removing one or both claws from the live animal and returning it to the ocean where it can regrow the lost limb(s). To be kept, claws must be 75 mm (2+7⁄8 in) long, measured from the tips of the immovable finger to the first joint.
In 1978, and in the Everglades National Park Research Center, wild caught crabs were kept in an aquarium for the specifics of testing mortality rates of declawed crabs. Mortality rates of 47 percent for doubly declawed and 28 percent for single declawed crabs were evident.[5] In the 2011 season the mortality rates had increased to 62.9 percent and 40.8 percent respectively.[6] In retrospect, 20 percent of landed claws are regrown.[7]
In the United States, Florida stone crabs are legal for harvest from October 15 until May 15.[8] The catch varies from year to year, ranging between 2.0 and 3.5 million in the period 1982–2009, overwhelmingly from the Gulf coast (as opposed to Atlantic coast).[7] This is believed to be the maximum amount possible, given current environmental conditions, regulations, and practices. The number of traps tripled between 1989–1990 and 2009–2010 without haul increasing (hence having a very low catch-per-trap level). However, due to fisheries management, the haul is believed to be stable, as sufficient spawning happens.
Claws are sold by size, generally in four sizes: medium, large, jumbo, and colossal.
The top buyer of stone crab claws is Joe's Stone Crab in Miami, and it plays a significant role in the industry, influencing the wholesale price and financing many crabbers.[9] The Monterey Bay Aquarium has given the Floridian stone crab fishery its highest rating of "Best Choice" for maintaining high fishing standards and working hard to keep the stone crab a viable fishery.[10]
The Florida stone crab (Menippe mercenaria) is a crab found in the western North Atlantic, from Connecticut to Colombia, including Texas, the Gulf of Mexico, Belize, Mexico Jamaica, Cuba, The Bahamas, and the East Coast of the United States. The crab can also be found in and around the salt marshes of South Carolina and Georgia. It is widely caught for food. The closely related species Menippe adina (gulf stone crab) is sometimes considered a subspecies – they can interbreed, forming hybrids – and they are treated as one species for commercial fishing, with their ranges partly overlapping. The two species are believed to have diverged approximately 3 million years ago.
