MS talks quite a bit about initiation temps and how that appears to affect initial upstream movement of adult steelhead on the North Shore. There are many ways to illustrate it, but we thought we would take it one step further. Previously we have focused on illustrating the daily creel numbers against temperatures and flow, and while this does a good job of showing you the granular interactions and how they appear to influence movement during pre and post-initiation threshold, we continue to try and find ways to actually validate the hypothesis. With the completion of the 2014 Spring creel, we now have enough historical data to begin doing that.
What you are looking at are each of the three regions of the Shore. We calculated the percentages of fish creeled prior to what is believed to be the initial upstream migration temperature initiation threshold vs. the post-initiation threshold. And while the results are not surprising (to MS at any rate), they certainly are interesting and of great value to the North Shore steelheader.
The week numbers, both negative and positive, are standardized for all years. Negative weeks represent all rainbows (steelhead + kamloops) captured prior to the hypothesized initiation threshold temperatures being attained. The "Zero" week is the point at which initiation threshold was reached, and subsequent weeks represent all rainbows captured post-initiation threshold. We also plotted the standardized "Magic 40" point. That is to say the point at which stream temperatures attained and maintained at or above 40 degrees F. The numbers are represented as percentages of the total return to creel as noted based upon pre and post-initiation, and the total sample size is noted for each region in the header.
Lower Shore Creel:
Interestingly what we are seeing is a fairly consistent 10-12% of fish being creel-sampled prior to the hypothesized temperature initiation threshold being attained, and the remainder peaking shortly after the threshold is attained, typically right around "Magic 40".
The oddball appears to be the Upper Shore. The current thought is that this isn't so much an anomaly with respect to the Upper Shore vs. the Lower and Mid Shore regions as much is it represents how people tend to fish steelhead during the spring runs. Not nearly as many people focus on the Upper Shore early in the run, but as the Lower and Mid Shore runs progress and begin to taper off, more and more anglers begin to focus efforts on the Upper Shore, which simply leads to more reporting.
Again, all we are doing here is figuring out more ways to validate the current hypothesis, but it also provides you with ways to apply the knowledge and become a more successful North Shore steelheader.
One last note: Minnesota Steelheader will take you creel reports any time you care to send them, Spring or Fall. We think it would be really interesting to begin to flesh out the entire year, so please keep sending the information via the creel page.