escapement

Salmon are counted at the end of their journey rather than the start. A run leaves the ocean, passes through ocean and river fisheries, and whatever survives that passage arrives on the spawning gravel. Escapement is the count of what arrives: the fish that escaped the nets and the hooks and reached a stream or a hatchery to breed. NOAA Fisheries defines it as the amount of salmon that return to a hatchery or stream to spawn.

It matters because it is the number managers steer by. Catch records what people took; escapement records what the river got, and that is what sets the size of the next generation. Fishing seasons are therefore shortened or widened to hit an escapement goal. Counts usually separate the fish that spawn in natural habitat from those returning to hatcheries, because only the natural spawners show whether a wild run can sustain itself. The counting is done on the ground: video weirs at river mouths, walked surveys of the spawning reaches, and counts of redds, the gravel nests the females dig.