Callinectes sapidus
The blue crab is a important bottom-dwelling predator and a member of the swimming crab family, Portunidae. It is widely distributed from Nova Scotia to northern Argentina, but along the coasts of North America, it is most abundant from Texas to Massachusetts. Blue crabs are opportunistic and will feed on a variety of live and dead fish, crabs, clams, snails, eelgrass, sea lettuce, and decayed vegetation. Male and female crabs can be distinguished by examining their segmented abdomen. The abdomen is folded and fitted snugly into a groove on the underside of the crab. The male's abdomen is long and slender, resembling an inverted "T". A female's abdomen changes as it matures; an immature female has a triangular shaped abdomen whereas, a mature female's is rounded.
Crabs grow by molting or shedding their shell. Just prior to molting, the crab is encased in both the hard, old outer shell and a soft, new one just beneath it. The formation of a new shell is evident along the margins of the swimming paddles of a crab. The earliest indication of the new skeleton is the formation of a black line along the rim of the paddles. When this line turns pink or red, the crab is referred to as a "peeler" or "shedder". Immediately after the molt, the crab's new shell is pliable and easily stretched. In this condition, the crab is called a "soft crab" or a "soft shell crab". Large amounts of water are consumed prior to and shortly after the molt, causing the soft shell to expand and increase in size. This entire process takes 2-3 hours and within 2 hours after the shed, the new shell begins to harden. The "papershell" is formed within 12 hours and an additional 2-3 days are needed before the shell fully hardens. Unlike male crabs that continue to molt and grow throughout their entire lives, females stop growing when they reach sexual maturity, usually after 21 or 22 molts. During this final molt, mating takes place.
Blue crabs mate from May to October in the brackish or slightly salty waters of Chesapeake Bay. Just prior to the final molt, an immature female crab, known as a "she-crab", is cradled by a mature male. The female is escorted by the male, commonly referred to as a "doubler", for a few days before and after her molt. During the molt, the male releases the female, but remains nearby. After molting, the female turns on her back and unfolds her abdomen. The male then transfers his sperm to the female. Although the female mates only once, she may spawn several times. The sperm received is stored and used to fertilize the eggs of all future spawnings. After mating, the two crabs resume the cradle carry until the female's shell hardens. Shortly after mating, the now mature female crab, known as a sook, migrates to the saltier waters of the Bay near the ocean. Adult males and immature females remain in the brackish waters of the Bay and its tributaries, migrating to shallow grassbeds, shallow muddy bottoms, and/or deeper waters of mid-Bay as temperatures begin to drop in the fall.
[young sponge crab with egg mass][mature sponge crab with egg mass]The female crab lays her eggs from 2 to 9 months after mating, depending upon when the mating took place. For example, a spring mating would result in a late summer spawn, while a fall mating would result in an early summer spawn the following year. Females develop an external egg mass on the underside of their abdomen which may contain between 750,000 and 8 million eggs, depending on the size of the crab. Young sponges are orange and gradually turn to brown and then black as the sponge matures. These crabs are called "sponge crabs" and hatching of the eggs occurs in approximately 2 weeks from June through September.
The newly-hatched larvae are called zoea and look nothing like an adult crab. These young crabs are microscopic in size and drift about in the water currents. It is believed that the majority of these developing larvae are transported into the ocean by an interaction of seasonal winds and bottom water circulation patterns, and eventually returned to settle on seagrass beds in the spawning area. After approximately 6 or 7 molts, the zoea changes into a post-larval form known as the megalops. The megalops has claws like a crab, but can swim and crawl on the bottom. Eventually the megalops settles and metamorphoses to the first crab stage which looks much like an adult crab, but is only 1/5 of an inch from point to point. As these young crabs develop their locomotion, they will migrate away from the high salinity waters near the mouth of the Bay up to more brackish regions. By winter, juvenile crabs can be found as far north as the Susquehanna Flats.
As winter approaches, most crabs will bury themselves in the mud and shallow grassbeds of the Bay. Female crabs will remain in the higher salinity waters of the lower Bay, whereas males will remain in the upper portions, migrating to deeper waters to spend the winter months. Little or no growth occurs from December to March, but when the temperature begins to rise, crabs become more active, begin feeding and searching for a mate.
Chesapeake Bay Management
The blue crab stock behaves as one unit throughout Chesapeake Bay; therefore, a unified management approach among Bay jurisdictions was initiated with the development of the 1989 Chesapeake Bay Blue Crab Fishery Management Plan (FMP). A comprehensive stock assessment of the Chesapeake Bay blue crab was also completed in 1996. The principal goal of this work addressed the status of the Chesapeake Bay blue crab population, the optimal levels of harvest, and management strategies to preserve this precious resource. After this assessment was completed, a revised 1997 Chesapeake Bay Blue Crab FMP was developed. This overall goal has not changed substantially from the 1989 FMP. The goal is: to manage blue crabs in the Chesapeake Bay to conserve the baywide stock, protect its ecological value, and optimize the long-term utilization of the resource. To achieve this goal, a sustainable and prudent level of spawning stock must be maintained; regulations must adequately protect the resource and optimize harvest; there must be fair allocation of the resource and minimal conflict among user groups; data must be collected to monitor and manage the fishery; research priorities need to be identified; submerged aquatic vegetation (SAV) should be protected and restored in lower Bay nursery areas; and water quality should be improved (For further information on the Plan or to obtain a copy, please contact Nancy Butowski).
The partners of the Chesapeake Bay Program, which include Maryland, Pennsylvania, and Virginia, the District of Columbia; the Chesapeake Bay Commission, a tri-state legislative body; the U.S. Environmental Protection Agency (EPA), representing the federal government; and participating citizen advisory groups, will continue to work towards the goals of this plan and furthering understanding of this complex creature. The Chesapeake Bay Commission's Bi-State Blue Crab Advisory Committee (BBCAC), with diverse membership from Maryland and Virginia, will continue to be a valuable forum to assure complementary approaches to blue crab management among the jurisdictions and insure that research needs are identified and pursued so that actions are timely and based on sound science.
[biologists doing a dredge survey]Maryland DNR fishery biologists use data obtained from commercial landings and surveys independent of the commercial and recreational fisheries to monitor crabs. The Maryland trawl survey, started in 1975, examines the abundance of both adult and juvenile blue crabs from May through October in the lower portions of the Chester, Choptank, and Patuxent rivers, Eastern Bay, and Tangier and Pocomoke Sounds. Maryland DNR, in a cooperative effort with the Virginia Institute of Marine Science (VIMS), also conducts the Chesapeake Bay Winter Dredge Survey. This survey randomly samples the entire Chesapeake Bay and its rivers during the winter months when crabs are inactive, and together, with the summer trawl survey, provides an important and consistent way to monitor Bay trends in the blue crab population.
Commercial and Recreational Fisheries
The blue crab is one of the most important species harvested in the Bay, and has the highest value of any commercial fishery and supports a recreational fishery of significant, but undetermined, value. Blue crabs are harvested as hard shell crabs, peeler crabs just prior to molting, and soft shell crabs immediately after the molt. For current minimum size and harvest limits, please check our updated commercial and recreational regulations information.
The hard crab fishery represents the largest commercial component of the crab fishery in Chesapeake Bay, both in terms of total dollar value and quantity landed. [bushels of crabs]Principal techniques for commercially harvesting hard crabs include trotlines, crab pots and dredges. The crab pot is the most widely used gear throughout the Bay and harvests approximately 60% of hard crabs landed in Maryland. Trotlines harvest approximately 40% of hard crab landings in Maryland, and the winter dredge fishery occurs exclusively in Virginia.
Soft and peeler fisheries use scapes, peeler pots and bank traps for the capture of soft crabs and peeler crabs for the soft-shell business and bait industry. Peeler crabs are also harvested as bycatch when they enter hard crab pots.
Three major license categories for commerical crabbing in Maryland currently exist. They include the Limited Crab Catcher License (LCC), which permits the use of trotlines and up to 50 crab pots; the Crab Harvester License (CB3), which allows for the use of trotlines and up to 300 crab pots; and the Tidal Fish License (TFL), which is a consolidated license for the harvest of finfish and shellfish, including blue crabs with trotlines and up to 300 crab pots. Both CB3 and TFL licensees may purchase additional allocations for up to 600 pots (1 allocation) or up to 900 pots (2 allocations), with the assistance of one or two unlicensed crew members, respectively.
Recreational gears include baited hand lines, mesh rings, collapsible traps, trotlines, and dip nets. Waterfront landowners are also allowed to use crab pots but now their crab pots need to include a Crab Pot Bycatch Reduction Device. For further information on the design of this device click here.
Blue Crab Fun Facts:
* Callinectes sapidus means "Beautiful swimmer that is savory".
* Crabs reach maturity in 12 to 18 months.
* Few crabs live longer than 3 years.
* The largest crab recorded from Maryland was a male measuring 9 inches; however bigger crabs (10-11 inches) have been captured in DNR crab surveys.
* The annual harvest of hard crabs from Chesapeake Bay accounts for over 50% of total U.S. landings.
* Cannibalism of young blue crabs by larger crabs is common and may regulate population abundance.
* A spring-spawned crab can reach a size of 2½ inches by their first winter.
The blue crab is a important bottom-dwelling predator and a member of the swimming crab family, Portunidae. It is widely distributed from Nova Scotia to northern Argentina, but along the coasts of North America, it is most abundant from Texas to Massachusetts. Blue crabs are opportunistic and will feed on a variety of live and dead fish, crabs, clams, snails, eelgrass, sea lettuce, and decayed vegetation. Male and female crabs can be distinguished by examining their segmented abdomen. The abdomen is folded and fitted snugly into a groove on the underside of the crab. The male's abdomen is long and slender, resembling an inverted "T". A female's abdomen changes as it matures; an immature female has a triangular shaped abdomen whereas, a mature female's is rounded.
Crabs grow by molting or shedding their shell. Just prior to molting, the crab is encased in both the hard, old outer shell and a soft, new one just beneath it. The formation of a new shell is evident along the margins of the swimming paddles of a crab. The earliest indication of the new skeleton is the formation of a black line along the rim of the paddles. When this line turns pink or red, the crab is referred to as a "peeler" or "shedder". Immediately after the molt, the crab's new shell is pliable and easily stretched. In this condition, the crab is called a "soft crab" or a "soft shell crab". Large amounts of water are consumed prior to and shortly after the molt, causing the soft shell to expand and increase in size. This entire process takes 2-3 hours and within 2 hours after the shed, the new shell begins to harden. The "papershell" is formed within 12 hours and an additional 2-3 days are needed before the shell fully hardens. Unlike male crabs that continue to molt and grow throughout their entire lives, females stop growing when they reach sexual maturity, usually after 21 or 22 molts. During this final molt, mating takes place.
Blue crabs mate from May to October in the brackish or slightly salty waters of Chesapeake Bay. Just prior to the final molt, an immature female crab, known as a "she-crab", is cradled by a mature male. The female is escorted by the male, commonly referred to as a "doubler", for a few days before and after her molt. During the molt, the male releases the female, but remains nearby. After molting, the female turns on her back and unfolds her abdomen. The male then transfers his sperm to the female. Although the female mates only once, she may spawn several times. The sperm received is stored and used to fertilize the eggs of all future spawnings. After mating, the two crabs resume the cradle carry until the female's shell hardens. Shortly after mating, the now mature female crab, known as a sook, migrates to the saltier waters of the Bay near the ocean. Adult males and immature females remain in the brackish waters of the Bay and its tributaries, migrating to shallow grassbeds, shallow muddy bottoms, and/or deeper waters of mid-Bay as temperatures begin to drop in the fall.
[young sponge crab with egg mass][mature sponge crab with egg mass]The female crab lays her eggs from 2 to 9 months after mating, depending upon when the mating took place. For example, a spring mating would result in a late summer spawn, while a fall mating would result in an early summer spawn the following year. Females develop an external egg mass on the underside of their abdomen which may contain between 750,000 and 8 million eggs, depending on the size of the crab. Young sponges are orange and gradually turn to brown and then black as the sponge matures. These crabs are called "sponge crabs" and hatching of the eggs occurs in approximately 2 weeks from June through September.
The newly-hatched larvae are called zoea and look nothing like an adult crab. These young crabs are microscopic in size and drift about in the water currents. It is believed that the majority of these developing larvae are transported into the ocean by an interaction of seasonal winds and bottom water circulation patterns, and eventually returned to settle on seagrass beds in the spawning area. After approximately 6 or 7 molts, the zoea changes into a post-larval form known as the megalops. The megalops has claws like a crab, but can swim and crawl on the bottom. Eventually the megalops settles and metamorphoses to the first crab stage which looks much like an adult crab, but is only 1/5 of an inch from point to point. As these young crabs develop their locomotion, they will migrate away from the high salinity waters near the mouth of the Bay up to more brackish regions. By winter, juvenile crabs can be found as far north as the Susquehanna Flats.
As winter approaches, most crabs will bury themselves in the mud and shallow grassbeds of the Bay. Female crabs will remain in the higher salinity waters of the lower Bay, whereas males will remain in the upper portions, migrating to deeper waters to spend the winter months. Little or no growth occurs from December to March, but when the temperature begins to rise, crabs become more active, begin feeding and searching for a mate.
Chesapeake Bay Management
The blue crab stock behaves as one unit throughout Chesapeake Bay; therefore, a unified management approach among Bay jurisdictions was initiated with the development of the 1989 Chesapeake Bay Blue Crab Fishery Management Plan (FMP). A comprehensive stock assessment of the Chesapeake Bay blue crab was also completed in 1996. The principal goal of this work addressed the status of the Chesapeake Bay blue crab population, the optimal levels of harvest, and management strategies to preserve this precious resource. After this assessment was completed, a revised 1997 Chesapeake Bay Blue Crab FMP was developed. This overall goal has not changed substantially from the 1989 FMP. The goal is: to manage blue crabs in the Chesapeake Bay to conserve the baywide stock, protect its ecological value, and optimize the long-term utilization of the resource. To achieve this goal, a sustainable and prudent level of spawning stock must be maintained; regulations must adequately protect the resource and optimize harvest; there must be fair allocation of the resource and minimal conflict among user groups; data must be collected to monitor and manage the fishery; research priorities need to be identified; submerged aquatic vegetation (SAV) should be protected and restored in lower Bay nursery areas; and water quality should be improved (For further information on the Plan or to obtain a copy, please contact Nancy Butowski).
The partners of the Chesapeake Bay Program, which include Maryland, Pennsylvania, and Virginia, the District of Columbia; the Chesapeake Bay Commission, a tri-state legislative body; the U.S. Environmental Protection Agency (EPA), representing the federal government; and participating citizen advisory groups, will continue to work towards the goals of this plan and furthering understanding of this complex creature. The Chesapeake Bay Commission's Bi-State Blue Crab Advisory Committee (BBCAC), with diverse membership from Maryland and Virginia, will continue to be a valuable forum to assure complementary approaches to blue crab management among the jurisdictions and insure that research needs are identified and pursued so that actions are timely and based on sound science.
[biologists doing a dredge survey]Maryland DNR fishery biologists use data obtained from commercial landings and surveys independent of the commercial and recreational fisheries to monitor crabs. The Maryland trawl survey, started in 1975, examines the abundance of both adult and juvenile blue crabs from May through October in the lower portions of the Chester, Choptank, and Patuxent rivers, Eastern Bay, and Tangier and Pocomoke Sounds. Maryland DNR, in a cooperative effort with the Virginia Institute of Marine Science (VIMS), also conducts the Chesapeake Bay Winter Dredge Survey. This survey randomly samples the entire Chesapeake Bay and its rivers during the winter months when crabs are inactive, and together, with the summer trawl survey, provides an important and consistent way to monitor Bay trends in the blue crab population.
Commercial and Recreational Fisheries
The blue crab is one of the most important species harvested in the Bay, and has the highest value of any commercial fishery and supports a recreational fishery of significant, but undetermined, value. Blue crabs are harvested as hard shell crabs, peeler crabs just prior to molting, and soft shell crabs immediately after the molt. For current minimum size and harvest limits, please check our updated commercial and recreational regulations information.
The hard crab fishery represents the largest commercial component of the crab fishery in Chesapeake Bay, both in terms of total dollar value and quantity landed. [bushels of crabs]Principal techniques for commercially harvesting hard crabs include trotlines, crab pots and dredges. The crab pot is the most widely used gear throughout the Bay and harvests approximately 60% of hard crabs landed in Maryland. Trotlines harvest approximately 40% of hard crab landings in Maryland, and the winter dredge fishery occurs exclusively in Virginia.
Soft and peeler fisheries use scapes, peeler pots and bank traps for the capture of soft crabs and peeler crabs for the soft-shell business and bait industry. Peeler crabs are also harvested as bycatch when they enter hard crab pots.
Three major license categories for commerical crabbing in Maryland currently exist. They include the Limited Crab Catcher License (LCC), which permits the use of trotlines and up to 50 crab pots; the Crab Harvester License (CB3), which allows for the use of trotlines and up to 300 crab pots; and the Tidal Fish License (TFL), which is a consolidated license for the harvest of finfish and shellfish, including blue crabs with trotlines and up to 300 crab pots. Both CB3 and TFL licensees may purchase additional allocations for up to 600 pots (1 allocation) or up to 900 pots (2 allocations), with the assistance of one or two unlicensed crew members, respectively.
Recreational gears include baited hand lines, mesh rings, collapsible traps, trotlines, and dip nets. Waterfront landowners are also allowed to use crab pots but now their crab pots need to include a Crab Pot Bycatch Reduction Device. For further information on the design of this device click here.
Blue Crab Fun Facts:
* Callinectes sapidus means "Beautiful swimmer that is savory".
* Crabs reach maturity in 12 to 18 months.
* Few crabs live longer than 3 years.
* The largest crab recorded from Maryland was a male measuring 9 inches; however bigger crabs (10-11 inches) have been captured in DNR crab surveys.
* The annual harvest of hard crabs from Chesapeake Bay accounts for over 50% of total U.S. landings.
* Cannibalism of young blue crabs by larger crabs is common and may regulate population abundance.
* A spring-spawned crab can reach a size of 2½ inches by their first winter.
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