Nehalem 2009 Escapement
The spawning escapement, 4070 (CV = 18%) was estimated using mark-recapture methods. Returning fish were captured by using nets and weirs and then marked with opercular punches. Subsequent carcass surveys were used to recover marked and unmarked fish from the spawning grounds. Since there was no terminal sport fishery in 2009, no creel survey was necessary.
Siletz 2009 Escapement
This mark-recapture program relied on nets and weirs to capture returning fish in the lower river, which were then marked with opercular punches. Carcasses were examined for marks at the spawning grounds. A creel survey was also conducted to estimate removals of marked fish by the terminal sport fishery. The preliminary spawning escapement was estimated at 2,270 Chinook salmon (CV = 13%).
http://www.psc.org/pubs/TCCHINOOK11-2.pdf
posted by Ty Wyatt
The above information was displayed by request as there is an ongoing debate on Ifish.net (http://www.ifish.net/board/showthread.php?p=3900776#post3900776).
ReplyDeleteSome curious clues to the variation in the two population estimates is going on here is that mark recapture methods have varied over the years and are very inconsistent in their accuracy to estimate population size.
Additionally, notice the ODFW goals are much higher than the PST goals. This is due to the fact that PST utilizes MSY on the 30 year average while ODFW comes up with a higher more conservative goal.
In all likelihood chinook escapements are moderately to grossly underestimated and in-river harvests are over estimated. This leads to PST allocating more of Oregon’s chinook to Northern Intercept Ocean Fisheries.
Ty Wyatt