I live near Puget Sound in WA State and there has recently been an effort to remove derelict gillnets that were lost. Approx 1200 derelict gill nets have been recovered and approx 1200 more have been indentified and are too deep for divers to recover and the group doing the removals have run out of funding. Some of the nets removed are estimated as being over 50 years old. These are monofilament nets that keep on killing even though there is no evidence of them on the surface. At one net location, there were over 2' deep of fish and crab skeletal remains under the net. These nets have killed millions of marine birds, fish, crabs and other sea life.
While Washington has not yet tried to ban gill nets, currently there is a proposal to make marking the net with the owner's information and a requirement to report the position and time of the net if it becomes lost so that it can be removed promptly. It is amazing how much resistance this simple requirement is facing from the commercial fishing lobby, although I have contact several of my friends who run gill nets and they all agree with the change.
Gill nets are a highly destructive type of fishing here and many are opposed to this type of gear. There some alternatives being run in test fisheries that look very promising and will hopefully allow more native fish to survive and the commercial fleet to remain prosperous.
If you would like any of the scientific data showing the kills of one single net, let me know and I'll be happy to share it with you. I'm sure that there must be derelict nets in Chesapeake Bay doing the same things.
Todd