Photos taken by different cameras and lenses, and also the way anglers hold fish can be deceptive to the eye, as is the size of anglers holding fish! Some look too big or small for the weight stated! You have to do research on the capture/weight history of a particular fish and then scrutinise scale patterns and markings, fin shapes, eyes, barbels, and ID markings etc. etc. Identifying a particular re-captured fish is sometimes very easy, but sometimes not so easy, because of the gap between captures which can be years. With this, the ID marks such as re-generated scales, warts, fin erosion and re-generation, weight fluctuation and length and girth size and so on, can change and heal. When I first saw the pic of the fish, first impression was that I thought it was not as heavy as the stated weight. Photos can be deceptive as stated above!
Looking closer, it is a known fish with a track record of nearing the stated weight when previously caught. The weight fluctuation process through summer and winter can be great or small depending on each individual fish! There are other factors also that help us come to conclusions such as contacting the witnesses and captor for questioning and the story of the captor/capture. All this is done to keep the river record list as accurate as possible, and is done on a voluntary basis which takes time and at our own expense. Originally, the list was initiated and undertaken by Brian Dowling who has since retired from doing so. In more recent times, Dave Mason and Rob Swindells have been the core of this, doing most of the direct investigations, with me as an advisory capacity if problems in identification arise. Hope this puts a bit of light on this as it is essential to keep the list going.