From a joint State-Tribal draft management plan (1990-an oldie but what's changed?)
"Escapement. A purpose of fisheries management is to ensure achievement of a desired level of catch. In order to maintain this level, it is necessary to prevent the capture of a certain portion of the run, so that these uncaught fish can spawn and producce fish for future use. An escapement allowance must be evaluated primarily according to whether it achieves the catch objective."