Except, as hard as they may wish, there are no ossicles in fish. You might think this quite unfair, but fish do not live in air, so they simply do not care. Air flows through the middle ear 'til a cochlear impasse does appear. From air to liquid, sounds abate, hence the ossicles must vibrate. From the ear drum vibrations play, setting the ossicles on their way.
Hammer moves anvil moves stirrup and so sounds amplify at the oval window.
Now sound increased many-fold enters the cochlea strong and bold. So that you may hear this story told.