One of the most direct methods for protecting a pond from birds is to use a physical barrier. Netting is a typical solution for this because it will easily blend into the water.
You can also place a small dock, perhaps a canopy, or even a gazebo-like structure over some of the pond for some level of protection from birds and other predators.
Creating a hiding place for the fish, such as a rock structure that overhangs the edges of the pond, can also help. A fishing tunnel and cave can also add dramatic visual elements.
A more creative way to deter birds from your fish pond is decoys. A big, ominous-looking owl statue next to the pond may deter smaller birds from approaching that area.