Blue crabs are 10 inches (25cm) in length, with carapace width of 20 inches (50cm). Their growth is highly dependent on temperature. If the water temperature is below 50 degrees Fahrenheit (10 °Celsius), blue crabs decrease in growth, while on temperatures over 59 degrees Fahrenheit (15 °Celsius) they strive and reach maturity by the second year. The lifespan of blue crabs is around three years.
Blue crabs are considered good swimmers. During evolution, the last pair of their legs has adapted to a paddle-like shape which helps them swim faster and easier. They can cover long distances on a day-to-day basis. They can travel 460 feet (140 meters) per hour, usually during daylight, but the total distance is approximately 820 feet (215 meters) per 24-hour cycle.
Spawning of the blue crabs is closely related to the region inhabited. After mating, female Chesapeake Bay blue crabs swim to the south port of the bay, and fertilize eggs with stored sperm that is almost a year old. Baby crabs come out as larvae and float for weeks. In North and South Carolina, spawning peaks in summer, while in the in the Gulf of Mexico, there are two spawning periods: one in early spring, and one in late summer. It is interesting that unlike males, female blue crabs mate only once in lifetime, in the period of their lives known as pubertal molt. During the molt, they release pheromones which attract males and force them to protect the females until the end of the molting period. Female blue crabs produce around 2 to 8 million eggs during the mating period, which lasts up to 15 weeks. Eggs need around 15 days to hatch.
Blue crabs are omnivores and eat plants and animals. Their diet usually consists of bivalves, small fish, plants and human waste. It was observed that they have an influence on the population of other crabs, which they sometimes eat, especially in the Chesapeake Bay area where a decrease of the invasive green crab was noted.
Blue crabs are a highly valued fishery species. From 1987 to 2001, the U.S. commercial catch of Callinectes sapidus was around $143 million. The Indian River Lagoon Blueway (IRL), which consists of a five-county area (Volusia, Brevard, Indian River, St. Lucie, Martin counties) has the highest commercial catch rate of 18 percent of the total U.S. numbers.