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Blue Crab Research at SERC

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Migration

Blue crabs live throughout the Chesapeake Bay, particularly in shallow near-shore areas where there is plenty of food to eat an bay grasses to protect them against predators. The blue crab's migration pattern is closely connected to its life cycle and really begins when blue crabs mate and the female crabs swim to the mouth of the Bay to release their eggs.

Let's follow the blue crab's journey up and down the Chesapeake Bay.

Mating throughout the Bay

When a female blue crab is ready to molt into a mature crab she doubles up with a male blue crab. After she molts and becomes a soft shell crab, the crabs can mate. Mating takes place in late summer and early fall and throughout the Chesapeake Bay.

 

Going south

After mating, the female crab migrates to the southern part of the Chesapeake Bay. During this journey, she fertilizes her eggs with the sperm she had kept after mating. (She may keep some sperm for a second spawning, which may occur nearly a year later.) Then, in November or December, she releases her brood of eggs near the mouth of the Bay.

Floating larvae near the mouth of the Bay

The larval stages of the blue crab can't swim and simply float in the water, passively riding the ocean currents. When the eggs hatch, the zoea--the first larval stage--float in the ocean waters near the mouth of the Bay. Four to five weeks later, when the zoea molts into a megalopa, the megalopa drifts back into the Bay, carried by the currents and tidal flow.

 

Junvenile crabs swim back up

When the megalopa molts into a juvenile crab, the crabs are finally able to walk and swim. Using the tidal currents and keeping to the shallow areas and underwater grasses, the juvenile crabs migrate up into the Bay.