Nice image here and getting the fish adds drama to it. Since you are looking down, you were able to get the fish's eye and combined with the nice catch light in the bird's eye that is appealing. A head turn slightly towards you would have put the bird parallel to the camera. That is desirable in many cases. I would add some room to the back and crop off the top. Rule of Thumb: Side to side should be 2/3 distance in front of the bird and 1/3 distance in back of the bird. Distance being from the bird to the frame edge.
The fish definitely enhances the subject captured. I am sure the post was leaning as captured, but might be worth a bit of CC rotation just to lessen the illusion it creates. Just a wee bit will not tilt the bird to much. At the risk of a very minor cloning suggestion and only if you are comfortable with such work ethically, the white bird dropping mark on the post, although natural, might be worth removing.
Jan
I sure like the bird with the fish......much more interesting. Well done on getting such nice detail and sharpness as well as good exposure. I agree with Robert on the composition.