Coping with continual danger: assessing alertness to visual disturbances in crucian carp following long-term exposure to chemical alarm signals.

Chemical alarm signals in fish are passively released into the water from ruptured epidermal cells, and induce instant fright responses in conspecifics. Fish also display alarm responses to injured heterospecific skin, as well as to scent of piscivorous predators that have ingested prey. A conspicuous alertness to visual disturbances has also been observed in fish following long-term exposure to extracts of filtered, homogenized skin, but the chemical inducers of such vigilance are actually unknown. We tested if a continual exposure to water-soluble alarm signals, from either conspecifics or heterospecifics, affects alertness of fish. Based on previous experience, it was assumed that alertn…