Professional Anglers Association

Salmon Details

Olfactory Pit from which the fish gets its sense of smell. The aperture covered by a flap of skin which acts as a valve, leads to an olfactory sac containing pleated (to increase the surface area) sensory epithelium. Salmon have a particularly strong olfactory response to water from the river of birth.

Eye In humans, the difference between the refractive index of the aqueous humor and air, accounts for 50% of the effort of converging the light rays. The fish is situated in water, whose refractive index is similar to the aqueous humor, so to achieve a similar focussing effect the eye lens is spherical with a high refractive index of 1.65. To focus, the whole lens is moved, as in a camera (forward for near vision, backwards and downwards for distant vision). The eye is equivalent to a camera with an extremely wide angle of view and great depth of field.

Lateral Line The lateral line is the row of external holes forming neuromasts connecting to the lateral line cranial nerve. It acts as a dynamic pressure detector, with a frequency range of 1 - 200 hertz. As this is a 'sense' that humans do not have, it is difficult to interpret how fish use it. It is thought that it helps fish identify fast, strong currents be aware of approaching objects, especially ahead (distant touch)