Albert R. Mann Library
Brown trout

The openings to a fish’s olfactory organs. Unlike nostrils, nares are not connected to the throat or the respiratory system. Trout have an olfactory sac on each side of the head, just under the skin; each sac has two nares. The sacs and nares are lined with cilia, which keep water flowing into the front nare and out the rear nare.

A trout can detect odors in concentrations of just a few parts per million; its sense of smell is estimated to be 500 to 800 times more acute than that of a human.