place ropes over water on poles about 8ft high and about 4ft between and place foil or like strips off them and this would deter them,( rope a bummer for using rods tho) ,should keep goosanders and cormarants at bay make a few dummys but depends on the flight of the water, around the pond /pigeon scarer worth a try seen this on a few ponds inflatibles are a option also
not sure if your mate would get a licence tho a think that your only aloud to shoot 3 a year and have to bag them up and send to them ( not sure if this has changed now tho)
only acouple of thousand are aloud to be shot ea