I've never really noticed it, but then again I tend not to want to cook things I see on the Saturday shows immediately, even though I may already have the ingredients, some of them in the freezer.
It always seems strange that there seems to be massive overabundance of some things and a dearth of others. My local fishmonger and Morrisons will either have shedloads of sea bass or none. Monkfish is something that rarely appears locally, sometimes it's even rare in Fleetwood! Monkfish is often mentioned on these programmes but the shortages don't coincide with the shows.
So I'm not too sure about the relation to TV cooks.
Though the Observer informs me that there will be demand for several things shortly, due to the forthcoming
Delia book.