Reproduction

After spending much of the winter in a dormant state burrowed in the mud, blue crabs will mate in early spring and through summer.  During this time, females go through a final molting stage to reach sexually maturity at an age of 12 to 16 months and they only mate once in their lifetime.  The females release pheromones through her urine to attract males during this terminal molting phase and males will mount the females and deploy a sperm sac that is stored in the females.  The females will migrate from shallow, near-shore mating grounds to further out to sea where salinity is 20 ppt to 32+ ppt while the males stay behind and continue to mate with other females.  

The females will often spend the winter after mating burrowed in the mud while the stored sperm fertilizes the eggs.  After the winter passes, the females finally extrude a sponge-like structure containing 1 to 8 million fertilized eggs from the abdomen and release them into the sea (note: because of the female migration to spawning grounds, there is 2 to 9 month lag time between mating and spawning).  Eggs will hatch in water that has a salinity of 23 ppt to 33 ppt and is 19˚C to 29˚C in temperature.  In bay environments, the eggs are released near the mouth of the bay and carried away by the ebb tide that drains water from the bay.