The way the numbers work is you have an estimate of run size (forecast or ISU), escapement goal, and estimates of harvest/encounters. In the pre-season, a mortality level for the NOR Chinook was set. When reached, based on either dead fish in the boat or x% of encounters, the fishery closes.

Management is based on the best numbers available at the time the decision is made. You have to have a reason to open a fishery. There could 15,000 "extra" hatchery fish in the river but of you are managing for wild fish then if you can't prove there aret any left to kill then you are done. That is the problem with having commingled hatchery and wild fish and bring to "protect the wilds".

Back in the 70s WDF was faced with the twin problems of bing unable to meet wild Chinook escapement goals and having excessive hatchery surpluses. Their solution? Lower the goal. They patted themselves on the back for eliminating the twin problems of surplus and under escapement.