Feeding ducks and not swans on the estuary

Help,
Been feeding maize out on an estuary, ducks were building up nice. Then I noticed fewer ducks but maize gone, in fact huge amounts.
The mud had disappeared under the feeder, which is a trough at water level (high tide mark) in about a meter of water.

There were a few swans around, which weren't there before, watching them they chased away any mallards who swam a little close.

So I need a plan or system to stop the swan, I was thinking about netting, but the tide may clog it with weed and take it out to sea on the next out going tide.

Anybody got a good system.

Thanks

Shoot the swans :D

There is a guy up our way (Tauranga) who is pretty handy with his ski boat. What he did was sick - my comment is a sad attempt at humour!!

I would be suprise if he still owns that boat!

Have chased them off when we can but they keep coming back, shootings a no go.

My shooting mate topped it up and there were twenty odd swans now, what's the point if we are only feeding swans.

Was thinking about a roof system but wondering if the swans will just swim under,

maybe some stakes and nylon at neck level:ouch...it hurts:

Good thought, we did try that and they just plough through!
We have one in the area with a bit of fluorocarbon decoration,
We had thought about a hot wire as well just a bit higher than the ducks, that might just be enough a couple of good hits,

Piano wire?