“Bokeh” comes from the Japanese word ボケ meaning “blur” or “haze” and refers to the aesthetic quality of the out-of-focus parts of a photograph. Bokeh is determined both by the type of aperture in a lens (number and shape of blades) and by the optical quality of the lenses in use. Some lenses allow you greater control over this aspect of photography by using multiple apertures in a single optical pathway. Those people using third party lenses on modern mirrorless cameras can purchase additional aperture modules to place between the lens and the camera body to reproduce this control, while almost all lenses can use a shaped blackout filter on the front lens element to control the overall shape of the bokeh artifacts.
However, heron don’t care about any of this. Heron just wants a fish.