Jonah Crab

Jonah crabs have been reported at depths of up to 2,460 ft (750 m). Habitat preferences for Cancer borealis range from rocky substrate in Rhode Island and the Gulf of Maine to silt and clay substrate on the continental slope. It is widely accepted that this species moves offshore in the fall and winter, and females have been documented moving inshore in late spring and summer. The Jonah crab is known to move to areas of preferred temperature for behavioral thermoregulation. The preferred temperature of this animal changes depending on the temperature to which it is acclimated. The estimated average preferred temperature is 59.7 °F (15.4 °C). Because Jonah crabs are a strongly preferred prey item for gulls, their survivorship is highest in deep water. However, some crabs will forage at shallower depths and in the intertidal zone, where food is more abundant.

According to stomach content analysis on individuals from the Gulf of Maine, the diet of Cancer borealis consists of mussels, arthropods, snails, and some algal species. Blue mussels (Mytilus edulis) composed more than 50% of analyzed stomach contents.

Males and females grow at about the same rate before reaching a carapace width of 1.2–1.6 in (30–40 mm), which is about the size of gonadal sexual maturity. After this point, females grow more slowly than males. Males tend to mature at a smaller size than females, but only reach functional sexual maturity at around 5.02 in (127.6 mm), when they are capable of engaging in the copulatory embrace. Size at gonadal maturity is greater for populations at higher latitudes.

Jonah crabs have long been caught as bycatch in lobster traps. Once, they were considered a nuisance and a pest that stole the bait in the traps and they were thrown back in the sea by fishermen. In the past twenty years, particularly in New England, landings have increased due to increased fishing pressure and market demand. Landings of Cancer borealis in the United States rose from 2–3 million lb (0.91–1.36 million kg) annually in the 1990s to more than 17 million lb (7.7 million kg) in 2014. In 2014, 70.05% of landings came from Massachusetts, followed by Rhode Island with 24.43%. Jonah crabs are not managed federally in the United States, but instead are managed by individual states with interstate coordination by the Atlantic States Marine Fisheries Commission.