FYI - Fish can secrete chemicals into the water that act as signals to communicate to other fish. The chemicals are currently thought to be specific to each species of fish. Thus each species recognizes basically only the chemicals produced by their own kind. Numerous studies have been performed on this topic in past years. Some recent studies have worked with pike and minnows and predatory and escape behaviors.

Some fish are more sensitive to smells than other fish.

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management