STONE CRABS
Captivating Crustaceans of Citrus County

Beloved by seafood fans for their delicious claw meat, Citrus County’s stone crabs also provide a fascinating window into topics ranging from biological adaptation to the balance of conservation and commercial enterprise. After examining these dynamic decapods, one has a greater appreciation for the complexity of the aquatic life found in The Water Lover’s Florida and beyond.


One Crab, Two-and-a-Half Species

The best place to begin an examination of stone crabs is with their place in the world. Like all known life forms, stone crabs have received grouping under the taxonomic system of scientific classification, which places living things within a hierarchy of increasingly specific groups. This provides an easy way to see where stone crabs fit in at multiple levels of life on Earth.

Stone crabs are found in the domain Eukaryota, a broad biological category that includes everything from people to fungi—all life with cells containing a nucleus (the “brain” of the cell) and a cytoskeleton (the internal “scaffolding” of the cell). Within the domain, they form part of the kingdom Animalia. Animals are distinguished as being heterotrophic (consuming food producers like plants) and having cells without a rigid outer wall. Most creatures in the animal kingdom are also multicellular, capable of movement and have bodies built of multiple tissues.

Like insects and arachnids, stone crabs form part of the phylum Arthropoda, invertebrates with such characteristics as a segmented body, appendages, an exoskeleton and a ventral nervous system. They also belong to the crustacean sub-phylum, Crustacea, which includes the class Malacostraca. Meaning “soft shell,” Malacostraca species exhibit a thorax with six segments, an abdomen with six segments and a two-chambered stomach among their hallmark features. The class contains the order Decapoda—crayfish, crabs, lobsters, shrimp and prawns. Most decapods are scavengers and have claws well suited to the task.

Moving closer to stone crab species on the taxonomic scale, one progresses downward through the Pleocymata suborder (decapods that incubate eggs on the female’s swimming legs) to the infraorder of all crabs, Brachyura. Within Brachyura, crabs begin to resemble Citrus County’s stone crabs more and more as one passes through the superfamily Xanthoidea and family Menippidae to the stone crab genus itself, Menippe.

The coasts of the American Southeast are home to two stone crab species: Menippe mercenaria, the Florida stone crab (found from roughly peninsular Florida up to Central North Carolina) and Menippe adina, the Gulf stone crab (found from the Panhandle west along the Gulf Coast).

While these crabs are extraordinarily similar—so much so that the commercial fishing industry manages the two animals as one—their subtle differences have lead scientists to classify them as two different species. At first glance, the most obvious dissimilarity is color: Florida stone crabs are typically tan or gray and spotted, while Gulf stone crabs are more likely chocolate-colored or maroon and solid. Florida stone crabs also possess somewhat larger claws. Researchers have also noted variations in temperature sensitivity, habitat, reproduction and other traits invisible to the naked eye.

Yet, if one examined a stone crab from the coast of Citrus County, it would very likely be neither a Florida stone crab nor a Gulf stone crab. Rather, the crustacean would probably possess a combination of traits from both crabs, not fitting squarely into either species. It would likely be a hybrid, a combination form.

How is this possible? According to the Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute, scientists believe that Florida and Gulf stone crabs descended from a single shared ancestor species in a process that began about 3 million years ago.

At the time (the late Miocene period, properly speaking), high ocean levels had divided the Sunshine State into a cluster of islands, separating the once unified stone crab population into divergent geographic areas. Different environmental factors favored different mutations: Those crabs who lived in sandier, grassier environments developed a lighter coloring and became the Florida stone crabs; the crabs in muddier environments grew into the darker-colored Gulf stone crabs.

One crab became two.

As the sea receded to its current level, creating the Florida coastline we know today, the crabs’ millions of years of separation came to an end. The Florida stone crab and the Gulf stone crab populations began to merge and interbreed into hybrids in areas along the Gulf and Atlantic coasts.

Two crabs became two-and-a-half.

Citrus County lies towards the end of the Gulf area of intermingling, which stretches from the start of the “Big Bend” area to Tampa Bay. According to the Florida FWC, Citrus County’s stone crab population today reflects a high proportion of hybrids, including both intermediate crabs that fall between the Florida and Gulf species, and those more closely relate to the former.

In Citrus County and elsewhere, the fact that the species’ union produces viable offspring illustrates how close two crabs really are. If hybridization continues and spreads into populations of pure Florida or Gulf stone crabs, the Southeast may over time play host to a single stone crab species.

Two-and-a-half crabs could become one once again.


A Crab’s Life

Citrus County’s stone crabs begin life as tiny larvae, feeding on even more minuscule zooplankton animals and staying in near-shore waters or estuaries. Thirty-six days after birth, the larvae have gone through six distinct stages of development and emerged as juvenile crabs. Male stone crabs grow faster than females, although females have a longer lifespan (approximately eight years) than males (approximately nine years). Adult crabs are likely to be found in the sandy bottoms, sea grasses and shellfish beds just off the county’s coast, from the low-tide line to 20 feet deep.

The size of a stone crab is typically measured by the width of its carapace, the wide part of the exoskeleton . Large stone crabs have a carapace width of about 6 inches. Like all true crabs, stone crabs have five pairs of legs. The first pair is a set of claws that assist in gathering food and self-defense. One claw is the larger “crusher” claw, the other the smaller “pincher.” The crabs’ claws can crush with thousands of pounds of pressure per square inch, allowing them to crack open stalwart mollusk shells. A large stone crab claw could weigh as much as one pound. The crustaceans’ eyes also protrude from their carapace, enabling 360-degree vision.


Stone crabs reach sexual maturity about one year into their life, when the carapace of males grows to 2.8 inches wide and females’ grows to 2.5 inches wide. Mating cannot happen until after molting—male and female crabs molt several times during their lifespan—when female crabs have softer bodies. Then, the male crab courts the female for as much as 12 hours before fertilization. Ultimately, the female carries up to 1 million fertilized eggs in a sponge-like egg mass below its abdomen before the larvae emerge. Spawning season stretches from spring to autumn, and females spawn as many as six times a season.

Oysters, snails and other mollusks, as well as marine worms and other crustaceans, serve as primary sources of food for stone crabs. However, the crabs will scavenge aquatic carrion and even resort to eating sea grass when necessary. Octopuses, cobia, grouper and humans number among stone crabs’ primary predators.


From Sea to Seafood

Every year, the State of Florida has a seven-month stone crab harvesting season from October 15 to May 15. Both recreational and commercial crabbing are popular in Citrus County. Typically, crabbers use a baited trap to snare stone crabs, although some recreational harvesters dive for crabs.

Stone crabs are a renewable resource: Unlike lobsters or blue crabs, only the claws are taken, then the crabs are returned to the water—without significant harm to the crustaceans themselves. In much the same way many lizards can lose their tails when attacked and later regenerate them, stone crabs have the defensive ability to lose a claw without significant blood loss or lasting damage. If trappers carefully snap off the claw, it can grow back in about a year. Officials encourage crabbers to remove only one claw, which allows the animal better protection and helps ensure bountiful harvests in future years.

Amateur stone crab trappers need a saltwater fishing license. Individuals are permitted to have five traps and to accumulate and or possess, by volume, a gallon of legal size claws per day. The claw itself must measure a minimum of 2-3/4 inches as defined in the official state regulations. (Read the complete regulations here.)

However, most visitors to Citrus County will probably forgo the trapping experience and, instead, order a stone crab claw feast from one of the many local restaurants that feature this seasonal delight. Eaten cold with a dip in mustard sauce, or warm with melted butter, the stone crab is an authentic Floridian delicacy!

Whether guests decide to try crabbing for themselves, savor the flavors of a stone crab dinner or simply reflect upon these captivating crustaceans’ unique place in the natural order, they will have a unique experience of the richness of aquatic life in The Water Lover’s Florida.


Educational Links

Recreational Stone Crabbing Rules & Regulations
Official state regulations for recreational crabbers.

FishWatch – U.S. Seafood Facts
Stone crab facts and nutritional information from the National Marine Fisheries Service.

Wikipedia Florida Stone Crab Page
A solid introduction to Menippe mercenaria.

A Proposed Evolutionary History of Stone Crabs
A useful article by the Florida FWC’s Fish and Wildlife Research Institute. Includes a map of the geographic distribution of the two stone crab species, as well as hybrid areas.