As new information is developed we periodically see the goals reviewed and if needed new ones established.
Is there not some mandate for periodic review at a fixed interval, with readustment of the escapement goal if the best science indicates that is appropriate?
You are correct in that there are a variety of escapements that would be at MSY depending on survival conditions. When survival conditions are poor the escapements that would produce maximum harvests is lower than when those conditions are better.
This is a scary concept. As survival conditions get worse (ie ongoing habitat degradation brought on by "progress") the MSY escapement decreases. Sounds like a vicious circle to me... with this philosophy, over time, we just keep justifying greater harvests so we don't overescape the MSY capacity of the habitat.
Often in todays management the managers also consider what they (call) management imprecision - how sloppy their management is.
Run-size projections are just that... projections, with plenty of room for imprecision. If in fact they are shooting for a mid-point escapement ( as in your Skykomish chinook example), that at least helps to compensate for some of that imprecision. But how universal is it that the runs are managed for the "average" MSY escapement from one system to the next?
Another common management strategy today is to use exploitation rate management models
This works in theory if angling effort is a fixed constant. In practice, however, when the run sucks, people hear about it and angling effort diminishes.... a lot of folks just won't bother with fishing if they think there is a low likelihood of success. Exploitation rates plummet. On the flip side, if the run is exceptionally strong, everyone hears about it, angling effort skyrockets, and exploitation is much higher than anticipated.
So where am I going with all this? Not really sure. I guess my biggest concern is that there's such an emphasis on making sure we harvest every last "surplus" fish so as not to "overescape" the river, when in fact that overescapement concern is just artificially created by fish mangers keeping escapement goals at ridiculously low levels. All the forces at work here, both political and biological, seem to conspire to make sure those escapement goals stay that way!
I was once told that the entire Quillayute system is managed for an annual steelhead escapement of only 5500 fish (someone please step in to correct me if this is a gross misrepresentation). There are much smaller river systems in Alaska that get more than 5500 fish in one tide! Can there be that much difference in what constitutes a healthy escapement in one system and not the other?
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