I live in South Yorkshire and around where I grew up there are now quite a few 'nature reserves', these generally are on land affected by mining subsidence which over the years have flooded and formed shallow lakes.
They have been around for so long that they contain (quality) fish, probably naturally stocked from flooding rivers or maybe the transfer of eggs on the ducks and geese that enhabit them.
The old National Coal Board and local councils gave these area's to various nature trusts, who now manage them.
I have walked these area's and know that on nearly all of them there are sections where the general public are not allowed, only paying members of the trust can gain access.
One of these in particular is 'growing' at an alarming rate as more and more land is attached due to its unsuitability for commercial needs. Already 2 or 3 miles of one side of the River Dearne is now a no access / no fishing zone and if the people who run the site could get their own way I am sure that they would close the remaining bank.
The fishing in this river is now up an exceptional standard with a good head of mixed fishing availabe. Nearby is a large self stocked lake that is improving annually, unfortunatley this is now on the border of the 'nature reserve' and again its only a matter of time before it is swallowed up.
I am sure that the various organisations responsible for running these sites are not in the slightest way interested in the general public, unless they are paying the admission fee for an escorted tour.