In response to such findings, a group of state and federal scientists here, including Scholz, have joined to study the effects of pesticides on salmon. The researchers are reading published data to try to understand how pesticides might impact recovery efforts. Using behavioral tests and experiments that measure brain activity, Scholz studied the impact of pesticides more carefully by looking at its impact on smell. In the wild, salmon detect predators by compounds given off skin of mammals and from alarm-pheromones given off by other fish. When salmon detect these odors, they stop, drop in the water and wait for danger to pass.
Pacific salmon leave their home stream, swim out to sea and return one to six years later to spawn.
But only if they can smell. Scholz is testing the effect of diazinon on hatchery salmon. The levels of pesticide are in a range similar to what might be experienced in nature. In tests, the insecticide, which is used to kill crane flies and other bugs, is squirted into the water, followed by a signal that normally triggers the predator response. The fish exposed to diazinon do not respond to alarm pheromones.