In reply to JimR:
There are people that look at a beach and think, 'wouldn't those stones look nice in my garden?', so the take a load away. If everyone did that it would be a lot of stones.
On certain beaches, the stones have been paid for by the council and put there, I think to help stop erosion.
So people taking stones are 1) stealing and 2) undoing the councils efforts at stopping erosion.
Knowing the above, the fine does not sound so silly.