http://www.cialisaustralia.me
Blue Crab
  • The blue crab's scientific name—Callinectes sapidus—translated from Latin means 'beautiful savory swimmer.'
  • Blue crabs not only comprise the most valuable fishery in the Chesapeake Bay, but are major predators of benthic communities and are prey for many other fish species.
  • Blue crabs are sexually dimorphic, meaning sexes occur in distinct forms. Males have blue claws and a narrow abdominal apron (referred to as the Washington Monument). Females have red-tipped claws ("painted fingernails") and a broad abdominal apron (referred to as the Capitol dome).

 


 

Status

Biomass: Approximately 97 million female adult (age 1+) crabs were estimated to be present in the Bay at the start of the 2012 crabbing season. This number is below the recommended target but still above the recommended threshold number of 70 million female spawning-age crabs. The estimated abundance in 2012 was lower than observed in 2011 and 2010. However, 2012 saw the largest juvenile (age 0) recruitment ever recorded, with an estimated 587 million juvenile crabs.

The graphs below show abundance estimates of female adult crabs and juvenile crabs, respectively, from the annual Winter Dredge Survey results for 1990-2012.

bcfemaleabundance12-thumbright

bcjuvenileabundance12-thumbright

Biological Reference Points: With support from the Virginia Marine Resources Commission, Maryland Department of Natural Resources, and the NOAA Chesapeake Bay Office, benchmark stock assessments of the Chesapeake Bay blue crab have been conducted every three to seven years since 1992. The most recent assessment, completed in 2011, reevaluated biological reference points to ensure that success in rebuilding a sustainable blue crab population continues over the long run. The 2011 assessment generated new reference points for the female component of the blue crab population. These maximum sustainable yield (MSY)-based female reference points were recommended and eventually adopted as replacements for the previous Maximum Spawning Potential overfishing reference points, which took into account both males and females (see table below). Similarly, the 2011 stock assessment recommends replacing the empirical overfished age 1+ (both sexes) abundance threshold and interim target with an MSY-based threshold and target based solely on female age 1+ crabs.

 

 

Target

Threshold

2010 Stock Status

2011 Stock Status

2012 Stock Status

Exploitation Fraction

Current, female-specific

25.5%

34%

18%

25%

TBA

Previous, sexes combined

46%

53%

39%

45%

TBA

Abundance

(millions of crabs)

Current, female-specific

215

70

251

190

97

Previous, sexes combined

200

86

315

254

178

 

The Chesapeake Bay blue crab stock is currently not overfished, and overfishing is not occurring. This is true according to both the new recommended female-only framework developed in the 2011 benchmark assessment and the former management framework.

Overfishing: No

Overfished: No

Fishing and habitat: The blue crab is perhaps the most sought-after shellfish in the mid-Atlantic region, and is caught both commercially and recreationally. The majority of the catch is commercial. Blue crabs are usually harvested with simple gear: pot, trotline, handline, dip net, scrape, or dredge. Crab abundance tends to be higher in areas with ample cover, such as submerged aquatic vegetation. Most fishing gear used to catch crabs has little to no effect on habitat.

Male and female blue crabs have different life histories, and this affects the catch of blue crabs around the Bay. More female crabs are caught in the lower part of the Bay because they stay in higher-salinity water when they spawn. Males tend to stay in lower-salinity water. The maps below, generated by ChesapeakeStat, show the difference in male and female habitat distribution during the summer.

bcmalefemaledistribution-thumbright

By-catch: Sublegal-sized blue crabs, various finfish, turtles, and even some mammals are considered by-catch in the blue crab fishery. Perch and Atlantic croaker are prominent finfish caught in crab pots, while diamondback terrapins, river otters, and raccoons have been found in lost and/or discarded traps.

Aquaculture: Blue crabs must shed their hard carapace shell in order to grow, and experienced crabbers can quickly spot signs that the crab is about to molt. These 'peeler' crabs are held for a short time in shedding tanks until they molt. After molting, the soft-shell crabs are removed from the water and sold. These shedding tanks are monitored continuously through the day and night. The Blue Crab Advanced Research Consortium is a multidisciplinary research and development program that focuses on hatchery technologies to produce juvenile crabs for potential enhancement of the wild stock and the development of aquaculture techniques for the year-round production of soft-shell blue crabs.


Science and Management

Blue crabs are managed directly by state jurisdictions—the Maryland Department of Natural Resources, Virginia Marine Resource Commission, and Potomac River Fisheries Commission (PRFC). Collaboration between these three jurisdictions is essential to sustainable blue crab management on a Bay-wide basis.

The NOAA Chesapeake Bay Office chairs the Sustainable Fisheries Goal Implementation Team (Fisheries GIT) of the Chesapeake Bay Program, which is a forum for discussing fishery policy issues, including blue crab management. The Fisheries GIT comprises federal agencies, state fisheries managers, watermen, and additional stakeholders in the Chesapeake Bay. The NOAA Chesapeake Bay Office Chairs this team. The goal of the Fisheries GIT is to promote ecosystem-based fisheries management by providing sound science to support informed management decisions across all Bay jurisdictions.

Blue crab management decisions discussed by the Fisheries GIT are based on scientific recommendations from the Chesapeake Bay Stock Assessment Committee (CBSAC), a workgroup under the GIT. CBSAC was formed in 1985 and provides scientific advice to managers. Each year, CBSAC produces a Blue Crab Advisory Report to advise management jurisdictions as they set regulations for the blue crab fishery. Since 2010, the annual CBSAC Blue Crab Advisory Report has been officially endorsed by the Fisheries GIT. The 2012 Blue Crab Advisory Report and accompanying figures are available.

During the last decade, blue crab populations in the Chesapeake Bay reached some of their lowest numbers ever due to overexploitation and habitat degradation. In response to prolonged low abundance, CBSAC recommended new management actions. The timeline below describes important blue crab management decisions since 2008. Click on each year to view a more detailed account of that year and learn more about the important role of CBSAC, the Fisheries GIT, science, and the states.

 

YEAR

DEVELOPMENTS IN MANAGEMENT

2008

January: Chesapeake Bay Stock Assessment Committee (CBSAC) recommends an interim target abundance at 200 million adult (age 1+) crabs

Female-specific harvest regulations put in place for the 2008 season to begin population recovery

September: Chesapeake Bay blue crab fishery declared a federal disaster due to the recent population decline; state are eligible for federal disaster funds

2009-2010

Chesapeake Bay Executive Order Strategysets a new Blue Crab Outcome to "maintain sustainable blue crab interim rebuilding target of 200 million adults (age 1+) in 2011 and develop a new population target for 2012-2025"

Chesapeake Bay Program's Sustainable Fisheries Goal Implementation Team (Fisheries GIT) agrees to (1) ensure a revised population target is reached by 2012 and (2) support and continue interjurisdictional management through the Executive Order

2011

The NOAA-funded benchmark Chesapeake Bay Blue Crab Stock Assessment suggests new sex-specific management of the blue crab population with female-specific reference points: 215 million female adult crab population target and 70 million female adult crab overfished threshold

October: CBSAC recommends the new female-specific reference points to the Fisheries GIT Executive Committee

December: Female-specific reference points are adopted by the Fisheries GIT at their full team meeting

2012

States adopt and implement new female-specific reference points for the 2012 season

CBSAC begins developing a male-specific management target for the Fisheries GIT Executive Committee

Future

Continued development and assessment of male reference points

Fisheries GIT discussions about jurisdictional allocation and commercial and recreational accountability in the blue crab fishery

 


Life History and Habitat

Life history, including information on habitat, growth, feeding, and reproduction of a species, is important because it affects how a fishery is managed. The blue crab uses multiple habitats in the Bay throughout its life. Blue crab distribution varies with age, sex, and season: Blue crabs tend to be abundant in shallow-water areas during warm weather; in winter they are plentiful in the Bay's deeper portions. Males range farther up into the fresher waters of the Bay and its rivers than females, who congregate in saltier waters. Blue crabs are bottom-dwellers that use beds of submerged aquatic grasses as sources of food, nursery habitat for young, and shelter during mating, and molting.

Geographic range: Along the Atlantic Coast, the blue crab ranges from Nova Scotia to Argentina. Within the Chesapeake Bay, male crabs tend to prefer fresher waters in Maryland and upper tributaries, while females like the saltier waters in the mainstem and Virginia.

Habitat: Blue crabs occupy a wide variety of habitats throughout their life history. Offshore, high-salinity waters are used during early larval stages. Larvae move into the estuary and use intertidal marshes, seagrass beds, and soft-sediment shorelines as they grow. Crabs are highly tolerant of temperature and salinity variations and can live in just about any region of the Bay. Habitat loss and increased nutrient loading present the greatest threats to the population.

Life Span: Crabs generally live three to four years in the Chesapeake Bay and reach maturity in approximately 12-18 months. Determining age is extremely difficult due to the loss of hard parts during the molting process.

Food: Crabs are voracious predators and are considered scavengers, eating just about anything they can including fish, clams, oysters, mussels, snails, worms, and insects. They are extremely cannibalistic and are most vulnerable while in the soft-shell stage of molting.

Growth Rate: Growth of blue crabs is strongly affected by temperature. For example, up to 18 months is necessary for maturation in the Chesapeake Bay, while blue crabs in the warmer Gulf of Mexico may reach maturity within a year. In laboratory studies, growth virtually ceased at temperatures below 13° C (55° F), while the growth per molt was reduced above 20° C (68° F).

Maximum Size: The largest blue crab caught in the Chesapeake Bay was 10.72 inches and weighed 1.1 pounds.

Reproduction: Blue crabs mate and spawn from spring to fall (May to October) in the Chesapeake Bay. Male crabs tend to molt throughout their lives, while females have just the one 'terminal' or 'maturity' molt. Female crabs can mate only once during their lives (during their terminal molt when in the soft-shell stage), but store sperm for multiple spawnings. The male crab may cradle the female—a pose in which the two crabs are referred to as doublers—for a few days prior to her terminal molt to maturity, and may stay with her after mating while her shell hardens and to ensure another male doesn't mate with her. Females migrate to the mouth of the Chesapeake Bay to spawn and can produce between 750,000 and 3,200,000 eggs per brood. Eggs hatch into larvae and undergo a series of molts offshore in high-salinity waters. The larvae then migrate into the Bay, and a majority grow and mature in beds of submerged aquatic vegetation. Small crabs molt frequently, but molting decreases in frequency as crabs grow bigger.

Migrations: In general, males remain in lower-salinity waters. Females migrate to higher-salinity water to spawn. The creation of 'corridors' or 'sanctuaries' has been instrumental in protecting crabs as they travel among nursery, feeding, and spawning grounds.

Predators: Predation may play a major role in influencing the size of populations. Blue crabs are preyed upon by red drum, croaker, striped bass, and other blue crabs.

Commercial and Recreational Fishing Interest: Both

Distinguishing Characteristics: Five sets of legs, with major front claw and rear swimmeret. Males have blue claws and a narrow abdominal apron (referred to as the Washington Monument). Females have red-tipped claws ("painted fingernails") and a broad abdominal apron (referred to as the Capitol dome). Immature females have a triangular or V-shaped apron, narrower than the dome shape of the sook's apron.


Role in the Ecosystem

The blue crab is an integral player in the Chesapeake Bay ecosystem. Scientists continue to study the effects of predation on blue crab populations; the effect of blue crab on populations of their benthic prey species, such as soft clam; and the effect on the fishery as well as the effect of the fishery on the blue crab population itself. Due to the economic and iconic value of the blue crab, it is considered a keystone species influencing many aspects of the Bay's ecosystem.


Did You Know?

  • Blue crabs may be referred to as hard-shells (not molting), peelers (crabs about to molt), busters (crabs that have started to shed their old shell or molt), soft-shells (crabs that just molted and their shell has not yet hardened), jimmies (adult males), sooks (adult female hard crabs), she-crabs or sallies (immature females), and sponges or sponge crabs (adult females carrying eggs).
  • The blue crab is the Maryland state crustacean.

 

Updated August 2012