Yes, escapement goals have changed over time. The usual reason is because new and better information informs the change. For example, in the late 1960s, early 1970s, WDF set Chinook escapement goals at the average of the previous 10 years, largely because that is all the information they had. They felt Chinook runs were doing OK with those escapement levels, so that's what they set the goals at. This was followed by setting coho escapement goals based on estimates of coho smolt productivity per unit of estimated coho rearing habitat. For such a crude method it was actually pretty darn good considering how large and varied an area it covered. Some of these escapement goals were later modified as a result of tagging studies (both juvenile and adult) and calculating spawner:recruit relationships. In a few cases the escapement goals were increased, and in others they were reduced. And some, like Lake Washington sockeye, where there is a super-abundance of spawner:recruit data, the ridiculous goal remains unchanged.

Steelhead escapement goals (for wild fish) were first developed in 1984 based on extensive habitat use and productivity estimates in a dozen western WA drainages. Some of those goals remain in use and some have been modified by using spawner: recruit data.