Callinectes sapidus is preyed on by the red drum, Atlantic croaker, herons, sea turtles and humans. They are also an important link in the food chain, being both predator and prey. They feed on fish, aquatic vegetation, mollusks, crustaceans, and annelids.
Known Predators:
Callinectes sapidus is easily identified by its body color which is generally a bright blue along the frontal area, especially along the chelipeds (the appendages bearing a "chela" or pincher-like claw). The remainder of the body is shaded an olive brown color. To accommodate swimming, the fifth leg is adapted to a paddle-like shape, as is the same with other portunids. Females have broad triangular or rounded aprons and red fingers on the chelae, whereas in the male the abdominal flap, or apron, is shaped like an inverted "T". Callinectes sapidus can grow to 25 cm in carapace length (CL), with carapace width being approximately twice the length. Growth is rapid during the first summer, with crabs growing from 70-100 mm CL. By the second year, maturity is reached at carapace lengths of 120-170 mm. Callinectes sapidus grows to adult size after 18 to 20 molts.
Range length: 120 to 170 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful
Callinectes sapidus has an average life span of 1-2 years. Many are harvested by humans before they would die naturally. In the St. Johns River, some blue crabs survive to four years of age.
Range lifespan
Status: wild: 1 to 4 years.
Average lifespan
Status: wild: 2 years.
Typical lifespan
Status: wild: 1 to 2 years.
Callinectes sapidus, the blue crab, is a bottom-dweller found in a variety of habitats ranging from the saltiest water of the gulf to almost fresh water of the back bays. Especially common in estuaries, this species ranges into fresh water, and may be found offshore. The blue crab's habitat ranges from the low tide line to waters 120 feet (36 m) deep. Females remain in higher salinity portions of an estuary system, especially for egg laying. During times of the year when temperatures are colder, C. sapidus tends to migrate to deeper water.
Range depth: 1 to 36 m.
Habitat Regions: temperate ; tropical ; saltwater or marine ; freshwater
Other Habitat Features: estuarine
Although the natural range of Callinectes sapidus spreads from the western Atlantic Ocean from Nova Scotia to Argentina, it was introduced, accidentally or deliberately, into both Asia and Europe. It has also been introduced into Hawaii and Japan. Callinectes sapidus is mostly found from Cape Cod (Massachussets) to Uruguay, but is also found north to at least Massachusetts Bay.
Biogeographic Regions: nearctic (Native ); palearctic (Introduced ); ethiopian (Introduced ); neotropical (Native )
Callinectes sapidus eats a large range of foods. Typically this species eats clams, oysters, and mussels as well as almost any vegetable or animal matter. This species will scavenge freshly dead animals but not long dead animals. The crabs will sometimes also eat young crabs.
Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans; other marine invertebrates
Plant Foods: leaves
Primary Diet: carnivore (Piscivore , Vermivore, Eats other marine invertebrates, Scavenger ); herbivore (Folivore , Algivore); omnivore
Parasites are very common on Callinectes sapidus. Barnacles, worms and leeches attach themselves to the outer shell; small animals called isopods live in the gills or on the abdomen; and small worms live in the muscles. Although C. sapidus is a host to many parasites, most of these do not affect the life of the crab.
Commensal/Parasitic Species:
The main positive economic importance of Callinectes sapidus for humans is for food. The blue crab is often eaten because the meat is tasty and can be prepared in a number of ways. Commercially, crabs are captured in traps that are rectangular, two feet wide, and are made of wire. The crabs are lured in by being baited with freshly dead fish. In some areas, crabs are also caught in trawls and by trotlines. Many people also crab since it is easy and inexpensive. Although there aren't any harvest limits, there is a 5-inch minimum body width as measured from spine to spine.
Positive Impacts: food
Callinectes sapidus is both colorful and highly visually responsive, yet almost all studies of their courtship have focused on chemical cues. In the underwater environment of C. sapidus, visual cues may function more rapidly and over a longer distance than chemical cues. Given that C. sapidus is aggressive and cannibalistic, visual cues may allow them to quickly evaluate potential mates from safer distances. The crabs will use color vision and color in mate choice with males having a preference for females with red claw dactyls.
Communication Channels: visual ; tactile ; chemical
Perception Channels: visual ; tactile ; chemical
Callinectes sapidus is not listed by any conservation programs.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Callinectes sapidus usually goes through seven zoeal stages and 1 postlarval, or megalopal stage. Sometimes an eighth zoeal stage is observed. Larval abundance is greatest when the tide begins to recede, because the larval release often occurs at the peak of high tide. Blue crab larvae are advected offshore, completing development in coastal shelf waters. Typical development through the seven zoeal stages is between thirty and fifty days before metamorphosis to the megalopal stage. The megalopa persists between six and fifty-eight days. The megalopal stage returns to estuaries for settlement, and eventual recruitment to adult populations.
Development - Life Cycle: metamorphosis
There are no known adverse effects of Callinectes sapidus on humans.
Spawning peaks in Callinectes sapidus are closely associated with the region they inhabit. Unlike males, female C. sapidus mate only once in their lifetime, after the pubertal or terminal molt. When approaching this final molt, females attract males by releasing a pheromone in their urine. Male crabs compete for females and until molting occurs they will protect them. At this time mating occurs, and may last as long as 5-12 hours.
Mating System: polygynous
Callinectes sapidus is highly fertile, with females producing from 2 - 8 million eggs per spawn. When females are in their soft-shell stage immediately after molting, the males transfer their sperm to them for storage. The male then protects the female until her new shell hardens. The females will spawn two to nine months after mating, laying up to eight million eggs. Spawning season is from December to October, with a peak both in spring and summer. When females are ready to spawn, they fertilize the eggs with the stored sperm and place them on the tiny hairs of the appendages on their abdomen. The female is called a "sponge" or "berry" crab while she carries eggs like this. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. The megalops (or larvae) pass through eight stages in about two months before they begin to resemble adult crabs. Usually only one or two crabs survive to become adults, and they have a lifespan up to three years.
Breeding interval: Males mate more than once, during each mating season, where females only mate once in their lifetime.
Breeding season: All year, but spawning occurs mostly during the months of December until October.
Range number of offspring: 2 million to 8 million.
Average number of offspring: 1.
Range gestation period: 14 to 17 days.
Average time to independence: 2 months.
Range age at sexual or reproductive maturity (female): 12 to 18 months.
Range age at sexual or reproductive maturity (male): 12 to 18 months.
Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); broadcast (group) spawning; ovoviviparous
Males tend to stay and protect the female until she has grown her hard shell after molting, but males have no interaction with the young. The female will protect the young while they hatch, but do not have a significant role in parenting. This is because there are so many eggs, and the maturing time is much too long for her to watch over them. They have to be independent from the time they hatch, which is why most of them will die before they reach the adult age.
Parental Investment: pre-fertilization (Protecting: Male); pre-hatching/birth (Provisioning: Female)
Barnacles often attach themselves to Blue Crabs, especially in southern regions. The Striped Barnacle (Balanus amphitrite) and Turtle Barnacle (Chelonibia testudinaria) are found externally; a small goose barnacle, Octolasmus lowei, occurs in the Blue Crab's gill chamber, and the bean-shaped sacculinid barnacle Loxothylacus texanus attaches itself under the abdomen. A parasitic nemertean worm, Carcinonemertes carcinophila, is found on the gills of female crabs; on virgin crabs, it is pinkish, while on breeders it is red. (Gosner 1978)
Feeding experiments carried out by Harding (2003) suggest that the Blue Crab may be an effective predator of the Rapa Whelk (Rapana venosa), a large predatory gastropod from Asia that was discovered in Chesapeake Bay in 1998. Although mature Rapa Whelks are probably too large and well protected to be attacked by Blue Crabs, available data suggest that predation by Blue Crabs on juvenile Rapa Whelks might control whelk populations in Chesapeake Bay and other estuarine habitats along the North American Atlantic coast.
Except when they have recently molted and have still-soft shells, Blue Crabs are very aggressive when threatened, although they will also burrow into sand to hide (Gosner 1978; Pollock 1998).
Baldwin and Johnsen (2009) investigated mate choice in Blue Crabs, carrying out mate choice experiments using males and manipulated photographs of females. Their results indicated that courtship and mate choice behavior in Blue Crabs can be stimulated by visual cues alone. Males showed a preference for females with red claw dactyls ("pincers"). In binary choice experiments, males displayed more often to photographs of females with red claws than to those with white claws or black claws, strongly suggesting that these male crabs made their choices based on the hue of the red claws and, more broadly, that Blue Crabs are capable of color vision and use color in mate choice.
The Blue Crab (Callinectes sapidus) is found from Cape Cod to Uruguay, occurring especially in estuaries. It is a beautifully colored crustacean with bright blue claws--the mature female's claws are tipped in red--and an olive to bluish green carapace. The Blue Crab is a commercially important species and is popular with recreational crabbers as well. (Gosner 1978; Lippson and Lippson 1997). The Greek and Latin roots of its scientific name translate to "savory beautiful swimmer".
The Blue Crab (Callinectes sapidus) is found from Cape Cod to Uruguay, sometimes north at least to Massachusetts Bay (Gosner 1978). Blue Crabs have also been introduced accidentally or intentionally in Hawaii, Europe, Japan, and Africa.
Place et al. (2005) analyzed the complete mitochondrial genome of the Blue Crab.
The Blue Crab (Callinectes sapidus) is especially common in estuaries, where it ranges into fresh water, but may be found offshore to at least 36 meters (Gosner 1978). Females remain in higher salinity portions of an estuary system, especially for egg laying (Lippson and Lippson 1997). Blue Crabs migrate to deeper water in winter (Gosner 1978).
Lippson and Lippson (1997) describe the life cycle of the Blue Crab in Chesapeake Bay, Maryland, U.S.A., which is famous for its Blue Crabs. Blue Crabs spawn near the mouth of the Chesapeake from May to October. The sponge, or egg mass, which may contain up to 2 million eggs, adheres to the undersurface of the crab. The color of the egg mass is golden orange at first, but changes to black as hatching approaches. After a few weeks, small semi-transparent zoae larvae are released. Many of these larvae are swept out into the ocean, where they mix with Blue Crab larvae from other regions of the coast and, eventually, are blown into regional estuaries such as the Delaware and Chesapeake Bays. After additional molts, a second larval form, the megalops, is produced. The megalops, which resembles a tiny lobster, moves along the bottom and up into the Bay system, where it molts into a tiny but recognizable Blue Crab. By 12 to 16 months, the crabs have molted several times and reached sexual maturity at an average size of about 13 cm.
Several other Callinectes species overlap in range with the Blue Crab (C. sapidus). Callinectes similis is quite similar in appearance, but has 6 teeth along the front of the carapace between the eyes (often more technically described as "4 teeth, not counting the inner orbital teeth"), while C. sapidus has just 4 (or 2, not counting the inner orbitals)(Gosner 1978; Pollock 1998). It also reaches a size of only about 125 mm across (vesus 225 mm for C. sapidus). Callinectes similis is a common estuarine crab south of Cape Hatteras, North Carolina (U.S.A.), ranging into fresh water; from Cape May, New Jersey, south to Cape Hatteras it is usually recorded from depths of at least 9 meters or more and salinities of about 15 ppt (Gosner 1978; Pollock 1998). Other Callinectes species in the Atlantic/Caribbean/Gulf of Mexico region also have 6 frontal teeth (4, not counting inner orbitals), although the inner pair may be very reduced.
The last pair of the Blue Crab's legs are paddle-shaped for swimming. The shell is more than twice as wide as long with 9 marginal teeth (the 9th is a strong spine). The shell is usually olive or bluish-green above and the claws are bright blue below (young are paler). The male's abdomen is abruptly tapered, while the female's is more broadly rounded. Adults may reach a width of 225 mm between the tips of the longest spines. (Gosner 1978)
Blue Crabs feed on plants, shellfish, recently dead fish, and a wide variety of other prey they can kill or scavenge, including recently molted soft-shelled individuals of their own species (Lippson and Lippson 1997).
Blue Crabs are the basis for a commercially valuable fishery in many regions, but as with so many other fisheries, overexploitation has been a major problem. The Chesapeake Bay has traditionally been one of North America’s most productive fishing grounds, supporting the world’s largest Blue Crab fishery. However, sustained fishing mortality and environmental deterioration led to an ∼70% decrease in Blue Crab abundance in Chesapeake Bay during the last decade of the 20th century and first few years of the 21st, from an estimated 900 million crabs down to ∼300 million, with 45–55% of those crabs harvested annually. Even more alarming, studied have found that spawning stock abundance and biomass in Chesapeake Bay declined by 81% and 84%, respectively, around this same period. Consequently, the Blue Crab fishery, which in the early 1990s was a 52,000-ton, $72-million industry, declined to a 28,000-ton, $61-million harvest in 2004. A multidisciplinary, multi-institutional program was developed to study the basic biology and life cycle of the Blue Crab, develop hatchery and nursery technologies for mass production of blue crab juveniles, and assess the potential of using cultured juveniles to enhance Blue Crab breeding stocks and, in turn, bay-wide abundance and harvests. Basic biology and culture studies yielded methods to mass produce larvae and juvenile Blue Crabs in captivity. Juvenile crabs have been produced year-round, with excellent survival. During 2002–2006, over 290,000 cultured crabs were tagged and experimentally released into the bay’s nursery habitats. Cultured crabs survived as well as their wild counterparts, increased local populations at release sites by 50–250%, grew quickly to sexual maturity, mated, and migrated from the release sites to spawning grounds, contributing to the breeding stock as soon as 5 to 6 months post-release. (Zohar et al. 2008 and references therein) Despite their enthusiasm and optimism regarding stock replenishment efforts, Zohar et al. (2008) emphasize their view that in addition to mass rearing and releasing of Blue Crab juveniles, successfully restoring Blue Crab populations will require the integration of adequate management strategies to protect the wild and released animals until sexual maturity and spawning, with fishery and seafood industry, policymakers, environmental activists, and scientists all working together.
Paolisso (2007) explored the evolving role of the Blue Crab in the human culture around the Chesapeake Bay watershed.
Callinectes sapidus (from the Ancient Greek κάλλος,"beautiful" + nectes, "swimmer", and Latin sapidus, "savory"), the blue crab, Atlantic blue crab, or regionally as the Chesapeake blue crab, is a species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico, and introduced internationally.
C. sapidus is of considerable culinary and economic importance in the United States, particularly in Louisiana, the Carolinas, the Chesapeake Bay, Delaware, and New Jersey. It is the Maryland state crustacean and the state's largest commercial fishery.[2] Due to overfishing and environmental pressures some of the fisheries have seen declining yields, especially in the Chesapeake Bay fishery.
Unlike other fisheries affected by climate change, blue crab is expected to do well; warming causes better breeding conditions, more survivable winters, and a greater range of habitable areas in the Atlantic coast.[3][4] Whether this will have negative effects on the surrounding ecosystems from an increased crab population is still unclear.[3]
C. sapidus is a decapod crab of the swimming crab family Portunidae. The genus Callinectes is distinguished from other portunid crabs by the lack of an internal cartilaginous spine on the carpus (the middle segment of the claw), as well as by the T-shape of the male abdomen.[6] Blue crabs may grow to a carapace width of 23 cm (9 in). C. sapidus individuals exhibit sexual dimorphism. Males and females are easily distinguished by the shape of the abdomen (known as the "apron") and by color differences in the chelipeds, or claws. The abdomen is long and slender in males, but wide and rounded in mature females. A popular mnemonic is that the male's apron is shaped like the Washington Monument, while the mature female's resembles the dome of the United States Capitol.[5] Claw color differences are more subtle than apron shape. The immovable, fixed finger of the claws in males is blue with red tips, while females have orange coloration with purple tips.[7] A female's abdomen changes as it matures: an immature female has a triangular-shaped abdomen, whereas a mature female's is rounded.[8]
Other species of Callinectes may be easily confused with C. sapidus because of overlapping ranges and similar morphology. One species is the lesser blue crab (C. similis). It is found further offshore than the common blue crab, and has a smoother granulated carapace. Males of the lesser blue crab also have mottled white coloration on the swimming legs, and females have areas of violet coloration on the internal surfaces of the claws.[9] C. sapidus can be distinguished from another related species found within its range, C. ornatus, by number of frontal teeth on the carapace. C. sapidus has four, while C. ornatus has six.[10]
The crab's blue hue stems from a number of pigments in the shell, including alpha-crustacyanin, which interacts with a red pigment, astaxanthin, to form a greenish-blue coloration. When the crab is cooked, the alpha-crustacyanin breaks down, leaving only the astaxanthin, which turns the crab to a bright orange-red color.[11]
Organochlorides are found by Sheridan et al 1975 to be transferred to the C. sapidus hepatopancreas.[12]: 7 [13] They find that among organochlorides, DDT specifically is converted both to DDE and DDD in this crab.[14]: 491
C. sapidus is native to the western edge of the Atlantic Ocean from Cape Cod to Argentina and around the entire coast of the Gulf of Mexico.[15][16] It has recently been reported north of Cape Cod in the Gulf of Maine, potentially representing a range expansion due to climate change.[17] It has been introduced (via ballast water) to Japanese and European waters, and has been observed in the Baltic, North, Mediterranean, and Black Seas.[18] The first record from European waters was made in 1901 at Rochefort, France.[19] In some parts of its introduced range, C. sapidus has become the subject of crab fishery, including in Greece, where the local population may be decreasing as a result of overfishing.[19]
The natural predators of C. sapidus include eels, drum, striped bass, spot, trout, some sharks, humans, cownose rays, and whiptail stingrays. C. sapidus is an omnivore, eating both plants and animals. It typically consumes thin-shelled bivalves, annelids, small fish, plants, and nearly any other item it can find, including carrion, other C. sapidus individuals, and animal waste.[20] In salt marshes, C. sapidus will eat marsh periwinkles, Littoraria irrorata during high tides.[21][22] Although an aquatic predator, C. sapidus will remain in shallow pits in salt marshes at low tide and ambush intertidal prey such as fiddler crabs (e.g., Minuca pugnax) and purple marsh crabs (Sesarma reticulatum) [23] C. sapidus may be able to control populations of the invasive green crab, Carcinus maenas; numbers of the two species are negatively correlated, and C. maenas is not found in the Chesapeake Bay, where C. sapidus is most abundant.[24]
C. sapidus is subject to a number of diseases and parasites.[25] These include a number of viruses, bacteria, microsporidians, ciliates, and others.[25] The nemertean worm Carcinonemertes carcinophila commonly parasitizes C. sapidus, especially females and older crabs, although it has little adverse effect on the crab.[25] A trematode that parasitizes C. sapidus is itself targeted by the hyperparasite Urosporidium crescens.[25] The most harmful parasites may be the microsporidian Ameson michaelis, the amoeba Paramoeba perniciosa and the dinoflagellate Hematodinium perezi, which causes "bitter crab disease".[26]
In 2021, scientists from the University of Maryland completed DNA sequencing on C. sapidus's genome in Baltimore after six years of research to help better understand the species.[27] This genetic map is expected to help scientists understand how the blue crabs will be affected by climate change and warmer water temperatures, along with which mutations cause disease, traits that influence meat production, and which females have the best reproductive ability.[28]
Eggs of C. sapidus hatch in high-salinity waters of inlets, coastal waters, and mouths of rivers, and are carried to the ocean by ebb tides.[7] During seven planktonic (zoeal) stages, blue crab larvae float near the surface and feed on microorganisms they encounter. After the eighth zoeal stage, larvae molt into megalopae. This larval form has small claws called chelipeds for grasping prey items.[29] Megalopae selectively migrate upward in the water column as tides travel landward toward estuaries. Eventually, blue crabs arrive in brackish water, where they spend the majority of their lives. Chemical cues in estuarine water prompt metamorphosis to the juvenile phase, after which blue crabs appear similar to the adult form.[7]
A blue crab grows by shedding its exoskeleton, or molting, to expose a new, larger exoskeleton. After it hardens, the new shell fills with body tissue. Shell hardening occurs most quickly in low-salinity water where high osmotic pressure allows the shell to become rigid soon after molting.[29] Molting reflects only incremental growth, making age estimation difficult.[7] For blue crabs, the number of molts in a lifetime is fixed at about 25. Females typically exhibit 18 molts after the larval stages, while postlarval males molt about 20 times.[30] Male blue crabs tend to grow broader and have more accentuated lateral spines than females.[29] Growth and molting are profoundly influenced by temperature and food availability. Higher temperatures and greater food resources decrease the period of time between molts, as well as the change in size during molts (molt increment). Salinity and disease also have subtle impacts on molting and growth rate.[6] Molting occurs more rapidly in low-salinity environments. The high osmotic pressure gradient causes water to quickly diffuse into a soft, recently molted blue crab's shell, allowing it to harden more quickly. The effects of diseases and parasites on growth and molting are less well understood, but in many cases have been observed to reduce growth between molts. For example, mature female blue crabs infected with the parasitic rhizocephalan barnacle Loxothylacus texanus appear extremely stunted in growth when compared to uninfected mature females.[29] Blue crabs may reach maturity within one year of hatching in the Gulf of Mexico, while Chesapeake Bay crabs may take up to 18 months to mature.[30] As a result of different growth rates, commercial and recreational crabbing occur year-round in the Gulf of Mexico, while crabbing seasons are closed for colder parts of the year in northern states.
Mating and spawning are distinct events in blue crab reproduction. Males may mate several times and undergo no major changes in morphology during the process. Female blue crabs mate only once in their lifetimes during their pubertal, or terminal, molt. During this transition, the abdomen changes from a triangular to a semicircular shape. Mating in blue crab is a complex process that requires precise timing of mating at the time of the female's terminal molt. It generally occurs during the warmest months of the year. Prepubertal females migrate to the upper reaches of estuaries, where males typically reside as adults. To ensure that a male can mate, he actively seeks a receptive female and guards her for up to seven days until she molts, when insemination occurs. Crabs compete with other individuals before, during, and after insemination, so mate guarding is very important for reproductive success. After mating, a male must continue to guard the female until her shell has hardened.[29] Inseminated females retain spermatophores for up to one year, which they use for multiple spawnings in high salinity water.[31] During spawning, a female extrudes fertilized eggs onto her swimmerets and carries them in a large egg mass, or sponge, while they develop. Females migrate to the mouth of the estuary to release the larvae, the timing of which is believed to be influenced by light, tide, and lunar cycles. Blue crabs have high fecundity; females may produce up to 2 million eggs per brood.[29]
Migration and reproduction patterns differ between crab populations along the East Coast and the Gulf of Mexico. A distinct and large-scale migration occurs in Chesapeake Bay, where C. sapidus undergoes a seasonal migration of up to several hundred miles. In the middle and upper parts of the bay, mating peaks in mid- to late summer, while in the lower bay , peaks in mating activity occur during spring and late summer through early fall. Changes in salinity and temperature may impact time of mating because both factors are important during the molting process.[29] After mating, the female crab travels to the southern portion of the Chesapeake, using ebb tides to migrate from areas of low salinity to areas of high salinity,[32] fertilizing her eggs with sperm stored during her single mating months or almost a year before.[33]
Spawning events in the Gulf of Mexico are less pronounced than in estuaries along the East Coast, like the Chesapeake. In northern waters of the Gulf of Mexico, spawning occurs in the spring, summer, and fall, and females generally spawn twice. During spawning, females migrate to high -salinity waters to develop a sponge, and return inland after hatching their larvae. They develop their second sponge inland, and again migrate to the high-salinity waters to hatch the second sponge. After this, they typically do not re-enter the estuary. Blue crabs along the southernmost coast of Texas may spawn year-round.[30]
Commercial fisheries for C. sapidus exist along much of the Atlantic coast of the United States, and in the Gulf of Mexico. Although the fishery has been historically centered on the Chesapeake Bay, contributions from other localities are increasing in importance.[34] In the past two decades, most commercial crabs have been landed in four states: Maryland, Virginia, North Carolina, and Louisiana. Weight and value of harvests since 2000 are listed below.[35]
As early as the 1600s, the blue crab was an important food item for Native Americans and European settlers in the Chesapeake Bay area. Soft and hard blue crabs were not as valuable as fish, but gained regional popularity by the 1700s. Throughout their range, crabs were also an effective bait type for hook-and-line fisheries. Rapid perishing limited the distribution and hindered the growth of the fishery. Advances in refrigeration techniques in the late 1800s and early 1900s increased demand for blue crab nationwide.[29]
The early blue crab fishery along the Atlantic Coast was casual and productive because blue crabs were extremely abundant. In the lower Chesapeake Bay, crabs were even considered a nuisance species because they frequently clogged the nets of seine fishermen. Early on, the blue crab fishery of the Atlantic states was well documented. Atlantic states were the first to regulate the fishery, particularly the Chesapeake states. For example, after observing a slight decline in harvest, the fishing commissions of Virginia and Maryland put size limits into place by 1912 and 1917, respectively. Catch-per-unit-effort at the time was determined by packing houses, or crab processing plants.[29]
The early history of the recreational blue crab fishery in the Gulf of Mexico is not well known.[30] Commercial crabbing was first reported in the Gulf of Mexico in the 1880s. Early crab fishermen used long-handled dip nets and drop nets among other simple fishing gear types to trap crabs at night. Blue crab spoiled quickly, which limited distribution and hindered the growth of the fishery for several decades.[36] The first commercial processing plant in Louisiana opened in Morgan City in 1924. Other plants opened soon after, although commercial processing of hard blue crabs was not widespread until World War II.[30]
Louisiana now has the world's largest blue-crab fishery. Commercial harvests in the state account for over half of all landings in the Gulf of Mexico.[30] The industry was not commercialized for interstate commerce until the 1990s, when supply markedly decreased in Maryland due to problems (see above) in Chesapeake Bay. Since then, Louisiana has steadily increased its harvest. In 2002, Louisiana harvested 22% of the nation's blue crab. That number rose to 26% by 2009 and 28% by 2012. The vast majority of Louisiana crabs are shipped to Maryland, where they are sold as "Chesapeake" or "Maryland" crab. Louisiana's harvest remained high in 2013, with 17,597 metric tons of blue crab valued at $51 million.[35] In addition to commercial harvesting, recreational crabbing is very popular along Louisiana's coast.[30]
The Chesapeake Bay has had the largest blue crab harvest for more than a century. Maryland and Virginia are usually the top two Atlantic coast states in annual landings, followed by North Carolina.[35] In 2013, crab landings were valued at $18.7 million from Maryland waters and $16.1 million from Virginia waters.[37] Although crab populations are currently declining, blue crab fishing in Maryland and Virginia remains a livelihood for thousands of coastal residents. As of 2001, Maryland and Virginia collectively had 4,816 commercial crab license holders.[38] Three separate licenses are required for each of the three major jurisdictional areas: Maryland, the Potomac River, and Virginia waters.[39] While the Bay’s commercial sector lands the majority of hard crab landings and nearly all peeler or soft crab landings, the recreational fishery is also significant.[39] In 2013, an estimated 1.8 million kilograms (3.9 million pounds) of blue crab were harvested recreationally.[37]
Blue crab populations naturally fluctuate with annual changes in environmental conditions. They have been described as having a long-term dynamic equilibrium, which was first noted after irregular landings data in the Chesapeake in 1950.[40] This tendency may have made it difficult for managers to predict the severe decline of the Chesapeake’s blue crab populations. Once considered an overwhelmingly abundant annoyance, the declining blue crab population is now the subject of anxiety among fishermen and managers. Over the decade between the mid-1990s to 2004, the population fell from 900 million to around 300 million, and harvest weight fell from 52,000 to 28,000 tonnes (57,000 to 31,000 short tons). Revenue fell further, from $72 million to $61 million. Long-term estimates say that the overall Chesapeake population decreased around 70% in the last few decades. Even more alarming, the number of females capable of reproducing, known as spawning age females, has plummeted 84% in just a few decades. Survival and addition of juveniles to the harvestable crab population is also low.[41] Many factors are to blame for low blue crab numbers, including high fishing pressure, environmental degradation, and disease prevalence.[42] The 2018 reduction in H-2B visas available for seasonal workers is affecting Maryland's 20 crab processors, which typically employ about 500 foreign workers, but the effect this will have on the crab fishery is not yet clear.[43]
Many types of gear have been used to catch blue crabs along the Atlantic and Gulf Coasts.[29] Initially, people used very simple techniques and gear, which included hand lines, dip nets, and push nets among a variety of other gear types. The trotline, a long baited twine set in waters 5–15 feet deep, was the first major gear type used commercially to target hard crabs.[6] Use of commercial trotlines is now mostly limited to the tributaries of the Chesapeake Bay. In the Gulf of Mexico, trotline use drastically declined after invention of the crab pot in 1938. Crab pots are rigid, box-like traps made of hexagonal or square wire mesh. They possess between two and four funnels that extend into the trap, with the smaller end of the funnel inside of the trap. A central compartment made of smaller wire mesh holds bait. Crabs attracted by odorant plumes from the bait, often an oily fish, enter the trap through the funnels and cannot escape.[29]
Species other than blue crab are often caught incidentally in crab pots, including fish, turtles, conch, and other crab species. In Georgia, hermit crabs (Pagurus spp.), channeled whelk (Busycon canaliculatum), spider crabs (Libinia spp.), and stone crabs (Menippe mercenaria) were the most common species observed as bycatch in commercial crab pots.[44] Of important concern is the diamondback terrapin, Malaclemys terrapin. The blue crab and diamondback terrapin have overlapping ranges along the East and Gulf Coasts of the United States. Because the funnels in a crab pot are flexible, small terrapins may easily enter and become entrapped. Traps are checked every 24 hours or less, frequently resulting in drowning and death of terrapins. Crab pot bycatch may reduce local terrapin populations to less than half. To reduce terrapin entrapment, bycatch reduction devices (BRDs) may be installed on each of the funnels in a crab pot.[45] BRDs effectively reduce bycatch (and subsequently mortality) of small terrapins without affecting blue crab catch.[46]
Because of its commercial and environmental value, C. sapidus is the subject of management plans over much of its range.[16][47] In 2012, the C. sapidus population in Louisiana was recognized as a certified sustainable fishery by the Marine Stewardship Council.[48] It was the first and remains the only certified sustainable blue crab fishery worldwide.[49] For the state to maintain its certification, it must undergo annual monitoring and conduct a full re-evaluation five years after the certification date.[50]
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{{cite journal}}: Cite journal requires |journal= (help) {{cite journal}}: Cite journal requires |journal= (help) {{cite journal}}: Cite journal requires |journal= (help) {{cite journal}}: Cite journal requires |journal= (help) Blue crab escaping from the net along the Core Banks of North Carolina. Callinectes sapidus (from the Ancient Greek κάλλος,"beautiful" + nectes, "swimmer", and Latin sapidus, "savory"), the blue crab, Atlantic blue crab, or regionally as the Chesapeake blue crab, is a species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico, and introduced internationally.
C. sapidus is of considerable culinary and economic importance in the United States, particularly in Louisiana, the Carolinas, the Chesapeake Bay, Delaware, and New Jersey. It is the Maryland state crustacean and the state's largest commercial fishery. Due to overfishing and environmental pressures some of the fisheries have seen declining yields, especially in the Chesapeake Bay fishery.
Unlike other fisheries affected by climate change, blue crab is expected to do well; warming causes better breeding conditions, more survivable winters, and a greater range of habitable areas in the Atlantic coast. Whether this will have negative effects on the surrounding ecosystems from an increased crab population is still unclear.
