Telephone hotline helps scientists learn the secrets of blue crab migration
By John Barrat
Smithsonian Office of Public Affairs
By water, there are approximately 135 miles between the spot where Maryland's Rhode River empties into the Chesapeake Bay and the spawning grounds of the blue crab at the mouth of the bay in Virginia. For a female blue crab, that's a lot of crawling. Once female crabs mate—and they mate only once in their lives—they must soon migrate to their spawning grounds at the Chesapeake's mouth.
"Whether they walk, swim or both to their spawning grounds is unknown," says Robert Aguilar, a biologist at the 
Smithsonian Environmental Research
Center on the Chesapeake Bay. "The timing, route and mechanisms of their
migration are poorly understood."
To aid in the study of the female blue crab spawning migration, Aguilar is enlisting the help of Chesapeake Bay watermen. Monthly from June to October, Aguilar buys several bushels of live mature female crabs and releases them after he has attached to the back of each a numbered plastic tag that offers a "REWARD" if a toll-free phone number is called.
Any crabber who calls the hotline with a crab's tag number, capture date, location and depth earns $5. The crabber's name is then entered in a $200 lottery. In any given year, roughly 5 to 16 percent of the crabs that Aguilar tags and releases are called in.
This summer, Aguilar is releasing crabs at points along the western shore, on the Maryland side of the bay at the mouths of the Rhode River, the South River and the York River.
Because Aguilar records where each crab is released, he knows how far a recaptured crab moved, how much time the trip required and in what direction it traveled. "We can then map the timing and route of the mature female crabs as they move to their spawning grounds," Aguilar says.
Data collected since 1999 indicate that most female blue crabs begin their spawning migration in September and October, traveling along the deep areas near the main channel of the Chesapeake Bay.
This article originally appeared in Inside Smithsonian Research, Summer 2004.
