Well before you start criticizing forecasting you should first try to understand it, how to best interpret it, how it fits into the Fraser Sockeye assessment cycle, and the challenges as well as limitations forecasters face. The best place to start is the actual document:
http://www.dfo-mpo.gc.ca/csas-sccs/Publications/ScR-RS/2017/2017_016-eng.pdf
A probability of p50 basically assumes average survival. It’s the probability that the media, environmentalist and even fishery managers quote, but it’s a fallacy to see forecasts like this as a single point estimate. It happens every year. Although the modelling can get quite technical and confusing the uncertainty that surrounds these forecasts shouldn’t be. These forecasts need to be viewed as a “range” of probabilities. These reflect the variability in marine survival as well as the what we know about freshwater survival which also has challenges. For instance, see the bottom of page 16 in the document I attached. The inability to get a reliable smolt outmigration at Chilko in 2015 due to extremely high water levels in the spring represented a big obstacle in forecasting this season. Summers are generally a main contributor to escapement with Chilko making up most of this.
Secondly, the end of season run size are PSC estimates at Mission which also have their own uncertainty and challenges, so they should not be viewed as final run size. Also note that “total run size” and “total escapement” are not the same thing, so I hope the are not being used synonymously. We don’t know final 2017 escapements or final run size for 2017 yet.
So, before ragging on estimates take the time to understand.