Always difficult to call weight, but I have done a few trips to NZ where 20kg 'tail are rats...... 25+ start qualifying as fish.
I would "guess-timate" that one - a skinny fish - to be 15-17kg........ but we can't see the full legth of the fish and if the angler is tall (reference points) it may actually be a respectable fish.
Always difficult to validate these things.
Anyway - a nice 'tail!