Neat pic.
I've long held a theory that brookies, once they reach about 8", tend to be largely fish eaters. A small stream brookie has an enormous mouth in proportion to the rest of their body and they can certainly snarf down dace and sculpins.

I have data to support that theory This photo is one part of the evidence and I can think of at least five other brookies that I caught that have had partially digested fish in their mouths, including one fish that I felt compelled to extract that was, at one point, an eight inch brookie.. The other fish were to badly decomposed or not enough was visible to positively identify what they were. Gives a whole new meaning to slimy sculpin..