This is a dreadful thing to do, on a club lake in my hometown the wildfowl started disappearing, some people were seen taking birds and were challenged, they threatened violence (with a distinctly non-UK accent) so the club member sensibly left and called the Police who did very little. Eventually the lake was pretty much stripped of wildfowl, lucky to see a Moorhen now, let alone Ducks, Geese or Swans. More people seen taking fish now, everything they catch from Gudgeon to Carp and everything inbetween, all being put in a carrier bag.
What I'm getting at is that (and I hate to generalise because it is unfair) when our Eastern European friends take Wildfowl and Fish it's for the dinner table because in their Countries it's considered normal, however, shooting Swan's and just leaving the carcasses suggests it's just someone who's not right in the head who's killing for killing's sake. This makes it doubly important to catch them as such a disregard for life could spiral into smething more serious.
I don't mind saying that I'm a shooter (shotgun, rifle and air-rifle) and things like this just put a blight on all aspects of the other sport I enjoy, as usual it's just one or two individuals bringing the sport into disrepute. I know it's a less emotive/serious issue but it's similar to the fact that all anglers are tarnished byt the few who can't be bothered to take their rubbish home.
Cheers,
Steven.