IFish Fishing Forum banner

Columbia Fall Chinook Jack/Adult Coorilation Chart

2 reading
1.5K views 9 replies 7 participants last post by  freespool  
#1 ·
I thought about the coorilation between jack numbers and adult returns that someone on here had try to predict furture runs with.

So I did some research and built this chart from data on the Coumbia River DART page.
Image

Jack (age 2) numbers are compared with returns two years later representing the age class 4 (average adult age). There seems to be an interesting coorilation.
 
#5 ·
Thanks RM... I understand the age class composition and compared the numbers as comparing 2 and 4 only to sinplify the graph.

Pete... Looks like ocean survival may be the key reason for higher survivals of the older age classes.

Bear in mind, this is only a comparison and not a prediction... Just the positive coorilation between age 2 and age 4 adults....
 
#7 ·
Also interesting fact may be that Canada interceptions of the older age classes may have been greatly reduced starting in the early 90's... May explain the why the jack numbers where much larger in comparison w/ the adult numbers in the late 80's..
 
#8 ·
We hear a lot about Ocean conditions, jack counts and spill to predict adult returns. What seems to be missing to me is interception or harvest rates outside the Oregon and Washington.

I have heard that 50% of the fall run is caught in Alaskan and Canadian fishery's. If we are only working with 50% harvest survival to begin with, I don't think its out of realm that a 10-30% increase in interception rate is occuring up North. This could explain where the fish go, when we are so far off on estimates. I have heard, that 2001-2004 commercial fishing rates were curtailed in BC to protect their local stocks. These restrictions were eased in 2005. Is it coincidence that 2005 projections (northern stock) seemed to almost unilaterally under perform expectations?

I don't know of any major stocks other than coho, that have beat preseason predictions, and even then it wasn't by much. There is also a higher correlation between returning coho jacks and the following years return. Could it be we have greater control over harvest rates on coho (California-Washington) and that that leads to better accuracy in estimating the next years adult return?
 
#9 ·
Anyone want to compile a graph like that for the wild steelhead? It would be interesting to see....

Keith :grin:
Can't do it for steelhead...the jack returns are sporadic...not at all predictable (or sort of predictable) like salmon. Plus, the adults don't all die after spawning...Some steelhead stay an extra year in freshwater, too..
 
#10 ·
Can't do it for steelhead...the jack returns are sporadic...not at all predictable

It's my understanding that spring chinook jack counts are also unreliable for predicting future runs.



salmon hugger