I only went back to 1990, this year is worse than them all
1990 - 21 mil
1994 - 16.8 mil
1998 - 10.8 mil
2002 - 15.4 mil
2006 - 13 mil
2010 - 28.2 mil
2014 - 18.9 mill
2018 - 11 mill
Edit: Interesting note is 1998 and 2018 have the same estimated return however if you compare the catches of the two, they are not even remotely the same. I am not sure when they started the hydroacoustic program perhaps that's the difference.
https://psc1.shinyapps.io/PSC_In_Season_Fraser/
It's weird. 2018's hydroacoustic numbers were weirdly steady at around 20,000-60,000 fish per day from around August 27 to mid-September. Not surprised to see 2010's September numbers off the charts, with the number of Lates that year. 2002 had big numbers in that period (just a couple days later than 2010), but 2006 (which had slightly stronger Lates than 2002) had numbers that were comparatively low (like 50,000 compared to 500,000 a day).
If I had to guess, I'd assume that if the current estimates for Lates remain what they are (~1,200,000), that the hydroacoustic numbers for around Labour Day onward would be really low. Lates in 2011 were 1,125,000 (comparable to current estimates), and their numbers were in the 15,000 to 110,000 range a day from now until September 17 of that year.