Are you sure that swallowing a Senko has any ill effect on a fish?
The reason I ask is because I recall catching a rainbow (on a tip up) while ice fishing once that had swallowed the hook so badly that I had to keep it, and when I cleaned it, I found a Senko the length and width of my middle finger in its gut.
Presumably the rainbow had swallowed the Senko several months earlier (during the open water season), but, when I caught it, it seemd to still be "well nourished" and vigorous.