Where does escapement collide?

In fisheries management, escapement is the portion of a fish stock that evades the fishery in a given season and survives to reach the spawning grounds, so that "spawning escapement" is what replenishes the next generation. Hilborn and Walters's Quantitative Fisheries Stock Assessment treats escapement goals as the management target that sets how many fish must be allowed through to sustain the run. The referent is a count of surviving spawners, measured at weirs and counting stations and compared against an escapement goal, sharing only the word "escape" with a watch's release mechanism.[1]

Unit

The number of fish surviving the fishery to reach the spawning grounds

Recovery means

Stock persistence depends on escapement meeting the goal needed to replace the harvested generation

Measured by

Counted at weirs, sonar, and counting towers and compared against a set escapement goal

In horology, the escapement is the mechanism that stands between a timekeeper's driving power and its oscillator: it releases the gear train one step at a time while feeding a small impulse to the balance or pendulum to keep it swinging, so the train "escapes" in equal beats rather than running free. Rawlings's The Science of Clocks and Watches analyses the lever and other escapements and the way their geometry governs accuracy. The referent is a power-regulating linkage at the heart of a clock or watch, judged by how cleanly it locks, releases, and impulses, and it is unrelated to fish surviving a fishery.[2]

Unit

The locking-and-impulse action that releases the train one beat at a time

Recovery means

Not applicable

Measured by

Assessed by lock, drop, and impulse geometry and by the stability of the rate it sustains