I'm sure I remember hearing (a few years back) that the Zander was the biggest threat to UK fisheries ever known, that it was going to sweep through the UK eating everything in its path, breeding uncontrollably etc etc etc... Yet when you read reports of people trying to fish for them, there's the usual story of plenty of blanks and disspointing results.
I've eaten coarse fish in the past and I really don't think the entire readership of the guardian is about to buy a rod licence and start taking fish. Firstly, you need to factor in the equipment needed to get started in the first place, then consider the amount of time you'd need to spend in order to catch anything worth eating. Sure, you'd probably take a couple of small roach or perch, maybe a small pike if you get to grips with it... but is that actually going to feed the family effeciently, relative to the amount of time you've spent? An allotment will produce vegetables, as long as you put the work in. Fishing is nothing like as guaranteed.
And then there's the final part. Once this fish has been caught, it needs to be despatched - knocked on the head if you feel like making it quick or left to suffocate if you don't. Then when you get it home, it needs to be slit from its bum up to the gills and the guts taken out. Some of them come out easy, some of them are a bit more of a struggle. I'm familiar with this process, having gutted my own sea catch a few times and a small pike way back when I was a kid. However, for people who's idea of food preparation is opening a packet and slipping it in the pan, I think this could quite easily be a step they're not prepared for.