In the course of trapping experiments previously described (Andrews 1955, McHugh 1955), a question arose concerning deterioration of bait with time. It is fairly obvious to those who fish the traps that the condition of the bait changes. The smallest oysters die first, through predation by drills, crabs, and other enemies, and through smothering in the muddy bottom. Barnacles and other organisms on the shells also die from various causes. The valves of the dead oysters soon separate, and some are lost through meshes of the trap, so that the volume of bait also decreases. Stauber (1943) found that efficiency of traps decreased as the interval between lifts increased, He found. also that the catch increased significantly after rebaiting.
A series of 20 traps was fished from the Virginia Fisheries Laboratory pier from July 1953 to December 1955. Although the traps were not rebaited until early October 1954, the catch per trap was greater during the second summer. If bait does deteriorate, as Stauber (1943) and others have concluded, this increased catch must reflect an increase in abundance or availability of Urosalpinx in 1954. But by October 1954, the bait consisted mainly of isolated valves, and the · few surviving oysters were thick-shelled and blunt. It was decided to conduct a controlled experiment with these traps to test the effect of rebaiting. This.experiment began in October i954 and continued through the summer of 1955
