Other studies that have been performed on Cancer irroratus include studies of osmoregulation and salinity tolerance and the trapping interactions of rock crabs and lobsters. A minimal amount of information has been compiled on the osmoregulation of larval and post-larval crustaceans. In their early stages of development rock crabs are hyper-osmoconformers in order to adjust to their surroundings. As they become adults they adjust between being osmoconformers in higher saline solutions to being hyper-regulators in less concentrated media. Larger adult rock crabs were more effective regulators than smaller adult rock crabs. Cancer irroratus salinity tolerance changes throughout its life cycle. When first born the larva has a moderate tolerance towards salinity. Its tolerance decreases as it begins to develop and drops to a minimum when it metamorphoses into a megalop. However, once the rock crab reaches maturity its salinity tolerance increases again (Charmantier & Charmantier-Daures, 1991). It was discovered, that crustacean catch rates are effected if there are other animals in the vicinity of the trap. When large rock crabs were present near the trap it decreased the capture of smaller rock crabs. In comparison, when lobsters were placed around the traps there was also a reduction in catch rates of both the small and large rock crabs. These results showed that there was a significant effect on crustacean catch rates when rock crabs experienced interactions with other threatening organisms, (Miller & Addison, 1994).
As the rock crab industry continues to grow, it is having an undertermined effect on the conservation of the species. However steps have been taken to help prevent the overfishing of rock crabs. Organizations, such as the DFO, are monitoring and making efforts to maintain a steady population and reproductive potential by placing guidelines and restrictions on fisherman (Gendron, 2001).
US Federal List: no special status
CITES: no special status
Cancer irroratus were considered pests by fisherman catching lobsters because they were known to enter the lobster traps and steal the bait. However, once the rock crab industry began to develop they were considered a profitable item themselves (NJ Scuba, 1994-96). The rock crab fishery can have negative effects on the lobster industry. Lobsters are known to depend upon smaller rock crabs as a food source. As the number of fisherman exploiting rock crabs increases, the number of smaller rock crabs (including megalops) begin to decrease in number. This could cause a negative effect on the lobster industry by disrupting the lobster food supply (Gendron, 2001).
The rock crab industry provides economic benefits. This fishery in the Atlantic Ocean is generally new. Lobsters have been the most popular fishery in this region over the years. The rock crab fishery first began in the 1970's but took several years to grow into an industry. As more markets developed for the seafood industry interest began to rise about the rock crab. Regulations were created by the Department of Fisheries and Oceans (DFO) to ensure the safety and survival of the species. These restrictions included- mandatory licenses in order to fish for rock crabs, a quota for the number of rock crabs fisherman could catch at one time, a minimum size of rock crabs fisherman were allowed to keep, set at CW 102 mm, and a ban on catching females to help promote a minimal amount of reproductive potential. This industry shows great promise for the future as more areas are being discovered and explored for rock crab exploitation (Gendron, 2001).
Rock crabs are opportunistic feeders. Since they inhabit the benthic zone of the ocean from shallow waters to depths extending to 2,600 ft., their food source is limited to species that can survive in this zone as well. They eat an assortment of items including algae, polychaetes, mussels, gastropods, and various crustaceans including hermit crabs. An interesting thing regarding Cancer irroratus food habits, is their responsiveness and affinity to food types they were already accustomed to rather than to ones with which they were unfamiliar. After being continuously fed one of two species they had the capability of noticing the difference in odors exhibited by both species, and expressed a preference for the most familiar one. This showed that rock crabs are able to detect and respond to prey odors (Ristvey & Rebach, 1999).
Cancer irroratus inhabit the Atlantic ocean, and are extensively distributed along North America's east coast. Their range stretches as far north as Labrador, Canada and reaches southward to South Carolina, U.S. (Gendron,2001).
Biogeographic Regions: atlantic ocean (Native )
Cancer irroratus live in the benthic zone of the ocean (Ristvey & Rebach 1999). They are able to adapt to extreme variations in depth. The depths that they exist at range from deep waters at 2,600ft. to very shallow waters and occasionly well inland from the low tide line (NJ Scuba, 1994-96). They live on a variety of substrate types including rocky and loose material. Smaller crabs with the cephalorthorax width of about 50 mm tend to inhabit muddy or sandy bottoms, while other crabs seem to prefer the rocky bottoms (Gendron, 2001).
Aquatic Biomes: benthic
The rock crab's size varies considerably between males and females. A fully mature male can reach a cephalothorax width (CW) between 50mm-140mm (Gendron,2001), and range in weight from 49-202g (Miller & Addison, 1994). CW is measured as the distance between the two most lateral notches on the carapace (Miller & Addison, 1995). It is uncommon for females to surpass 100mm CW (Gendron,2001). The shape of a rock crab's shell is wide and oval. It is a yellowish color and frequently shades of red and purplish brown are visible. The different array of colors gives this creature a unique and colorful carapace. Another interesting characteristic of the rock crab is its denitition, or teeth. The rock crab has either nine broad and smooth or rough jagged teeth, depending on its diet (Gosner,1978).
Range mass: 49 to 202 g.
Average mass: 108.50 g.
Other Physical Features: ectothermic ; bilateral symmetry
Cancer irroratus reproduction occurs in the autumn. Sexual maturity in females is attained once they reach the CW size of 60 mm. Males have a slightly larger size of CW 70 mm at sexual maturity. Before mating commences, both male and female rock crabs moult their shell. This event for males happens during the winter months to ensure that their shells are completely firm before the fall. Females moult their shells during the fall so that they remain soft during mating. It takes rock crab shells between 2-3 months to fully harden. After fertilization females lay their eggs and store them under their stomach for almost a year. Depending upon the female's size the number of eggs produced can range from 125,000 to 500,000. After this period of time the eggs hatch and between the months of June to September the larva stay in the water column. By the time autumn returns the larva that were hatched metamorphose into extremely small crabs called megalops. For the first part of their life these young crabs are extremely vulnerable to predators and water turbulance. To increase their chance for survival they remain in shallow water and at the bottom of the ocean floor for protection (Gendron,2001).
Cancer irroratus (common name the Atlantic rock crab or peekytoe crab) is a crab in the genus Cancer. It is found from Iceland to South Carolina at depths up to 2,600 ft (790 m), and reaches 133 mm (5.2 in) across the carapace.
This crab species occurs on the eastern coast of North America, from Iceland to South Carolina.[1] Rock crabs live over a large depth range, from well above the low tide line to as deep as 2,600 feet (790 m).[1]
Cancer irroratus has nine marginal teeth on the front edge of the carapace beside each eye,[1] and reaches a carapace width of 5.25 inches (133 mm).[2] These crabs are similar in color to, and overlap in size with, the Jonah crab, Cancer borealis.[2] The two species can indeed be distinguished by the purplish-brown spots on the carapace of C. irroratus (contrasting with the yellow spots of C. borealis), and by the smooth edges to the teeth on the edge of the carapace (denticulate in C. borealis).[2]
The rock crab has recently become a popular culinary item. The name "peekytoe crab" refers to the fact that the legs are "picked" (a Maine colloquialism meaning "curved inward").[3] Until about 1997, they were considered a nuisance species by the lobster industry because they would eat the bait from lobster traps.[1]
Cancer irroratus (common name the Atlantic rock crab or peekytoe crab) is a crab in the genus Cancer. It is found from Iceland to South Carolina at depths up to 2,600 ft (790 m), and reaches 133 mm (5.2 in) across the carapace.
