A fair point. These lakes already suffer from the mass removal of pike through gill nets and catch and kill comps via section 59 exemptions. You also will have locals killing every pike no matter what size that they catch.
Coarse fish numbers are constantly on the rise on these lakes and they are bound to compete with trout for invertebrates. Factor is the usual suspects of slurry run-off, coniferous monoculture, livestock encroachment upon riparian zones, climate change along with increasing flooding of rivers and good old pike gets the short end or blame for any drops in trout numbers.
Back to your point about poachers putting up photos or using any new changes to the fishing regs to take advantage of what they might and probably are already doing
Several scientific papers state that pike have very little impact upon larger, deeper lakes above 1 km2 in size with alternative forms of fodder fish in abundance. Pike will do a lot of damage to smaller lakes where only salmonoids make up the greater fish biomass.
So if pike numbers drop considerably about the country will anglers then turn their attentions to trout and salmon? What sort of impact might this have upon their numbers if people don't bother with the catch and release anymore?