Obviously, fish do not possess the big fleshy ears. Talk about swimmer’s ear? Instead, sound transmits from the water into the fish body and to a set of internal ears. Keep in mind a fish’s body is about the same density as water, so the sound passes easily. These ‘ears’ are divided into the pars superior, the upper bit, and utriculus, the lower bit. The pars superior contains three fluid-filled semicircular canals, each filled with sensory hairs, allowing a fish to determine yaw, pitch, and roll. The utriculus possesses the otoliths, little bony plate that are denser than water. The difference between the movement in the fish and otoliths stimulate the cilia on the sensory hair cells.
Deep-sea fish may be better than their shallow water cousins at hearing. A graduate student at University of Maryland, Xiaohong Deng, will present in May at the Acoustical Society of America Meeting will present evidence that some deep-sea fish specialized structures to heighten their hearing, herring aids if you will. These adaptations included:
• a connection between the ears and swim bladder, the latter acting like a resonating chamber,
• elaborately-oriented hair bundles in the inner ear,
• exceptionally rigid ears and stalks projecting from stones in the ear, not seen in shallow-water fish and still bewildering.
Deng states, “We have already found many specializations and adaptations in the eyes and olfactory systems of deep-sea fishes; it is reasonable to think that their hearing should also be important in the dark,” says Deng.
Those trying for the Mile-Down Club may want to be a little quieter.