Curiosity has me asking why are they showing up there 2 years in a row. I don't think they are stocking in NB, but they are in MC, Portage, EC and St Joe.
Glad you brought this up, Tim! We can't know for certain, but it's probably a combination of food/temp/currents.
I can say for certain that it's almost completely unrelated to stocking location at this time of year. For the most part, we don't even begin to see staging until mid to late August.
I can't emphasize enough that the fish you are catching from March until mid-August on the south end have essentially zero to do with southend stockings. In fact, Indiana could not stock chinooks at ALL and you would never even notice a change in the spring and summer boat fishery - only about 2-3% of the kings caught out of our ports from March-August are of Indiana stocking origin. You'd only notice a change for mid-August to September.
The below snapshot from a Mass Marking Program presentation shows an example of chinooks recovered in the same district as they were stocked, by month. You can see that essentially during spring and summer, few chinooks are recovered near their stocking location. They're all mixed up, roaming around the lake. The proportion recovered in their stocking district starts creeping up in August, but really doesn't substantially change until September
Here's another very similar example. These pie charts show the stocking origin of chinooks landed in Grand Haven and Muskegon. Note that the pie charts for April-July and August are almost identical, especially the light blue slice, which represents chinooks stocked in Grand Haven and Muskegon and also recovered there.
And then once you hit September and October it's suddenly almost all fish stocked at that location