Confidence: It's likely to be this, but I can't be certain.
Notes: A 49cm brown trout appeared to have something large within its gut. It turned out to be 2 objects, 2 young roach the larger of which was 12.5cm long. Quite a few Phryganea caddisflies, approx 30 one inch perch fry and an aquatic snail were also found in the stomach. I can't say definitively that these aren't roachxbream hybrids for example but they have the characteristics of ordinary roach- red eyes and fins, silver body.