I don’t mind being in a minority on this point. I use a keepnet, if I want to and nothing particular – shallow water, low oxygen conditions etc – suggests I shouldn’t.
Given all the things done to fish within the sport – hooking, overpowering their impulse to flight, removing from the water, handling, weighing, photographing, I’m not too clear why retaining in a keepnet should be so reprehensible. It’s not necessary? Neither is all the rest, if you want to push that point.
I like to use a keepnet when fishing for shoal fish rather than larger specimens; balanced against this I’d say the fish I catch are out of the water being handled, filmed, admired, etc less than those of many who don’t. Whether that’s in videos made by the famous and well-respected, or on the bank by anglers who don’t have a keepnet but still manage to mess the fish around.
The argument against keepnets often begins with the phrase “Outside of matches……” If use of a keepnet is an unacceptable cruelty, what is there about combining fishing with competition and gambling that makes it ok? Net users use them for their pleasure, in a match or not – we’re just getting our pleasure in different ways. Either nets are ok for all or for none. The issue is brought into focus now that match fishing has gravitated to commercials. In matches, commercial owners are happy for anglers to stuff nets with huge quantities of large carp on hot summer afternoons, but not for me, as a pleasure angler, to amass 10lb of roach ( I don't fish for carp) in a large net on a cold winter's day.
Using a keepnet undermines angling’s public image? Most non-anglers, if the subject of fishing comes up between us, seem surprised that I don’t kill them and eat them (and a bit baffled, too, suggesting they would). None have ever disapproved of me keeping them in a big net sunk in the water.