fishbadger-
If you check you 2016-2017 fishing regulation pamphlet you will see that for MA 11 under the salmon season the following wording is highlighted in yellow

'"Season may close earlier if CHINOOK guidelines are attained."

The exact same wording can be found under the summer salmon seasons for MA 5, 9, 10, and 11.

That wording can also be found during the winter "blackmouth" seasons for MA 6, 7, 8-1, 8-2, 9, 10 and 11

Curt