Fish Communication

Fish Communication

     As a kid I used to stare at the fish tank in my house and think the fish were talking to each other when their mouths moved. I used to wonder what they were saying, stories they were telling each other. I would even make up some conversations. Eventually I grew out of believing that fish could talk. But I always knew that even if they weren’t actually speaking, they were still in fact communicating in some way. But the question was-How?



     Schools of fish communicate using pheromones. Pheromones are endogenous chemical signals secreted by organisms. They trigger an innate response in other members of the same species. The behaviors that are influenced by pheromones are sexual attraction, territorial demarcation, signaling alarm, and recruiting members together for feeding or defense purposes. “Some aquatic organisms may only respond to chemical cues during times of the day. Migratory adult sea lamprey are nocturnal and respond to migratory pheromones at night” (Johnson & Weiming, 2010). In some cases the communication reflects more than just the survival and reproduction of an individual organism, but also contributes to others in the species. Alarm substance pheromones are pheromones that alert and warn other group members of a nearby predator. Some fish species release a volatile substance when attacked by a predator that can trigger a flight response in members of the same species of fish. Pheromones are detected by the olfactory systems. These systems for detecting pheromones include olfactory sensory neurons, which are nerve cells with one end exposed to the external environment, often embedding in an otherwise impermeable skin or cuticle.



     “Experience and learning also alter behavioral responses of fishes to alarm substances. Several fish species exhibit learned predator recognition to alarm substances” (Johnson & Weiming, 2010). Minnows, which are small fresh water fish that belong to the carp family, are known to shoal in large numbers or schools. Their small size makes them easy prey for all the carnivorous fish and they rely on their speed and close shoaling habits to save them from predators. Minnows can react very quickly to danger signals. They release an alarm pheromone stored in specialized cells on its skin only when the skin is damaged, warning other minnows in the school that a predator has attacked. The flight response will cause the school of minnows to disperse in a frantic manner, then school up and gradually swim away from the source of the alarm pheromone. But not all schooling fish have traits of the flight response.

     In some cases different species that can produce alarm pheromones can pick up each other’s version of it so that if one fish of a different species is attacked other species in the area know to get away from the area. There have also been fish that once used the pheromone, but lost the ability to produce and detect it because it would interfere with their diet which consists of similar species, which is the case for piranha. “Some species undergo an ontogenetic shift where alarm substance responses are only elicited in young age groups, likely due to trade-offs between foraging and predation risk” (Johnson & Weiming, 2010).  It is said that alarm substance pheromones evolved for three main reasons. The first reason is that it came as a way to ensure survival of members of the same fish species because it warns them of the presence of a predator. They may have also evolved as a way to prevent fish from eating their own species, more specifically their offspring. If a fish bit a member of the same species it would have the same effect of them as if it was released from a fish under attack from a predator. The third possible reason for the alarm substance pheromone is that it has been recently hypothesized that predator fish have begun to be able to pick up the presence of the pheromone attracting them to injure fish and an easy meal. But as the number of predators in the area around an injured fish increases, so does the time it takes from first strike to until the time of ingestion. This allows the prey more time to free itself and possibly escape. Whatever the reason, pheromones are a vital part of a fish species survival.

     Knowing that pheromones play a huge part in the lives of fish species it makes me wonder about the age old argument of instinct versus intelligence. Can fish think or is everything solely based on nature’s cues passed down from generation to generation? Since evolution plays a huge role on a fish’s instincts, it has to affect fish species intelligence as well.

Works Cited

Johnson, N., & Weiming, L. (2010, October). Understanding behavioral responses of fish to pheromones in natural freshwater enviroments. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural & Behavioral Physiology, pp.701-711. Retrieved February 23, 2012, from the Complete Academic Database