It looks like the focal plane ended up around the angle of the jaws. I think it would be stronger in tis case is the sharpest focus was more on the front teeth.
challenge -- met technical -- the whole picture is slightly blurry. i'm assuming you used a tripod, if you didn't, it's always a good idea to do so. if you did, did you get too close for your camera to be able to focus? composition -- centering the fish works well here, i think a portrait would've been good, too, to cut down on the empty space and include the fins of the fish. -- gr8photos.