Protecting small pond from Herring Gulls

[hiacedrifter]

My new fish pond (approx 2 x 1 m) was doing very well for a year ... then the herring gulls discovered it, and have eaten all the fish. I have ordered some floating plastic protectors, but I am loath to cover it with a net (I did try, but it has lots of marginal plants so looks very messy with a net on). Is there anything else i could try? Some kind of perimeter barrier from hazel twigs or rocks?