The most likely reason for its extinction was the introduction of the lake and rainbow trouts, although insurmountable irrigation dams on the Truckee River and the commercial fishery may well have been contributing factors. Although much is known about the senses of sight, hearing, taste, smell, and touch in trout, a good deal remains to be learned. In its general form the eye of a fish is not unlike that of land vertebrates, but it is necessarily somewhat modified for vision under water. As most anglers know, trout do see quite well. It is an old question that was partially answered by tests conducted by Department of Fish and Game biologists.
Trout can distinguish certain colors.
They respond to red and all shades of red, including light pink. Perhaps they can distinguish many other colors too, but in these tests they were attracted only by red. The tests also proved conclusively that trout can see and are attracted by red objects entirely out of the water. The swim bladder is the main sound receiver, transmitting its vibrations to the inner ear, but the lateral line system is also a hearing organ. The latter is particularly sensitive in the low-frequency and subsonic range, and at short distances it can locate sound sources.