Fish reproductive pheromones release

In fish the olfactory sense is important, in a species-specific way, during various situations and behaviors. Chemical cues released from heterospecific and conspe-cific individuals provide information about the presence of food items, predators, competitors, mates and allow the recognition of kin (e.g. reviews Hara 1994 Olsen 1999). Several species of fish are dependent on the olfactory sense to detect sex pheromones during reproduction (review Stacey and Sorensen 2006). Pollutants can have effects on one or more links in the chemical communication chain between the individuals (see Fig. 26.2). The chemicals can affect the sender of the pheromone or the individual that detects the signal, the receiver. It is also possible that the pheromone is affected by biotic and abiotic factors, such as bacteria, organic materials and pH, when released into the water. 

We believe that the hormonal stimuli which have been found to affect fish physiology and behavior should be considered pheromonal in nature because they stimulate the olfactory system in highly specific manners at low concentrations and, when tested on the whole organism, often evoke specific, adaptive responses which do not appear to be learned (Sorensen, 1996). At least in fishes, hormonal products can exert special pheromonal actions on conspecifics without being specialized. This being the case, we define a sex pheromone as a substance, or mixture of substances which is released by an individual and which evokes in conspecifics a specific and adaptive reproductive response, the expression of which does not require specific learning. ... 

Communication Specialization of Pheromone Production. 5.3.2.1. Introduction and Evolutionary Origins. Whereas many fishes are expected to use hormonal pheromones for spying, others undoubtedly have come to use pheromones in communication. We expect the genesis of communication (pheromonal signals) in situations where there is a mechanism for individual donors to experience differential reproductive success because some aspect(s) of the way they produce and release a pheromonal cue can be modified to improve their individual success. In general, such mechanisms are expected in species... 

Bjerselius, R., Sorensen, P.W. Li, W. 1995b. Spermiated sea lamprey release a potent sex pheromone. In Proceedings of the Fifth International Symposium on the Reproductive Physiology of Fish (Ed. by F.W. Goetz P. Thomas), p 271. Austin TX Fish Symposium 95. 

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