Gone fishing

I had a walk along the river this morning with my daughter. I came across this man who was very excited at his catch, he was waiting for his friend to come to take a photo. I got in on the act when his friend arrived and asked if I could take his photo, he was keen to oblige. He did tell me what sort of fish it is but I’m afraid I’ve forgotten. His friend told me he’d also caught it before, he recognised it as it has a piece out of one of its fins. He assured me they always put them back in the river. It’s an activity I don’t really understand but I’m glad they return them to the river.