I wrote an article about this about a decade ago for Noreaster Magazine. I interviewed several commercial crabbers who said they lost up to 30 percent of their pots every years to boaters cutting the floats off.
The reason the pots are not in deep water is because the Chesapeake's waters are so polluted that there is not sufficient oxygen beneath a depth of 10 feet in the summer months to support any form of life. Consequently, the crabbers continually move their pots to shallower locations until they become productive - oven in depths as shallow as 5 to 6 feet.
When the water temperature drops below 72 degrees, and oxygen levels increase in deeper water, the crabs begin to migrate toward the channels of rivers and creeks and by early September the females are beginning to start their southern migration to the mouth of the bay where they'll spawn. As the water cools they'll go deeper and deeper, sometimes to depths of 40 to 50 feet as they approach the Virginia line. The commercial crabbers follow the crabs and the pots become more dispersed as fall approaches.
Keep in mind that nearly every form of edible seafood found in Chesapeake Bay has been exploited and depleted by commercial interests to the point where the only thing left that is viable is striped bass and blue crab. Oysters, soft-shell clams, hard-shell clams, several species of finfish and American eel have essentially been wiped out by overfishing. Only stringent regulations placed on striped bass and blue crab have managed to stave off extinction. And, striped bass during the late 1970s were essentially commercially extinct, thus resulting in the historic Striped Bass Moratorium.
Eventually, possibly within the lifetimes of some of our younger forum members, commercial fishing for all forms of marine life will cease to exist - if for nothing else, the salvation of what remains of wild stocks. Currently, there are a dozen aquaculture operations in Southeast Asia where crabs are successfully being propagated. And, because the demand for crab meat is beyond anyone's wildest imagination, U.S. buyers are traveling worldwide in search of new sources. The U.S. crab meat supplies have all but dried up - even in the south east states where crabs were once considered a nuisance to commercial finfish and shrimp netters.
If you see crab pots in a pot free zone, forget calling Maryland DNR - they will not respond. Instead, call the U.S. Coast Guard. The coasties will respond and take appropriate action.
Cheers,
Gary