[cppond]

I hope the below is helpful.


"Senses
The six senses of a fish are developed to different levels depending on the fish species and the environment in which it lives. The senses are:

• Sight - Compared to man, Koi are short-sighted, having a range of perfect vision of only 1-2 metres and blurred vision for approximately 10 metres. This is more than adequate underwater, where visibility is usually restricted by algae and sediment. Despite their" poor" vision, Koi can see in colour with their detection of yellow and green being most accurate.
• Smell - Koi have a very good sense of smell. The olfactory organs responsible for detecting smells are located all over the head and anterior part of the body, but are concentrated in the nares and barbels. It has been estimated that goldfish have a sense of smell that is fifty times better than in humans.
• Taste - Taste receptors are located both inside and outside the mouth, allowing the fish to taste its food before ingesting it. Outside the mouth they are mainly located on the lips and barbels.
• Touch - Touch and pressure receptors are present all over the body of the Koi, but are concentrated on the head and barbels.
• Hearing - Fish have an inner ear situated at the back of the head, which can detect vibrations, orientation and pressure changes. To increase its sensitivity the inner ear is connected to the swirnbladder(which acts as an amplilier) by means of a chain of small bones. If the swimbladder is punctured sound perception is reduced to 2% of its original level.
• Lateral Line - The sixth sense of a Koi is the lateral line. This organ can be seen by means of a row of scales, each with a hole in it, running along the side of the fish. Under the scales is a canal which runs from the head to the base of the tail. The canal is filled with a jelly-like substance and contains man pressure wave sensors called neuromasts. Any vibrations in the water cause the jelly-like substance and consequently the neuromasts to vibrate. Nerve endings in the neuromast detect the movement. Slight differences in both the intensity of the stimulus and the time when each neuromast detects it, allow the Koi not only to detect movement but also ascertain from where it originated."

http://www.akca.org/library/behavior.htm