As a lad I saw some pound and pound-and-a-half roach weighed (sadly, I had no part in their capture), so when a man came round asking all and sundry if they had a spring balance, because he'd just caught a roach that might be three pounds, I dug out my Little Samson four-pounds scale and we set off to weigh Leviathan. "Pound and a half", I thought, at first sight, and the scales confirmed this. The poor chap looked crestfallen and puzzled, saying "It looked much bigger than the two-pounder I caught last week!"
Gudgeon - at about six inches, they seem to change from a roughly triangular cross-section to an almost square one; this should mean that beyond six inches they will get much heavier for a relatively small increase in length. It wouldn't surprise me if the record was only about eight inches long - does anyone know?