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About Pheromones (animal body odors) Released By Fishes And Their Importance In Aquarium And Pond Keeping (Revised)
What are pheromones? They are semiochemicals that are "chemicals emitted by plants, animals and other organisms…that evoke a behavioral or physiological response in individuals of the same or other species. They include pheromones and allelochemicals. (Advisory Committee on Pesticides, 2004: 13)."
Pheromones are mainly known to us as natural human and animal body odors externally released as secretions and chemical scents from specialized body cells, including by exogenous or exocrine glands. These pheromones produce a spontaneous reaction from those producing the pheromones as well from those around them. The ability to produce pheromones is widely present in animals. It is also described for plants, such as for mushrooms and flowering plants. We particularly know of pheromones in man as body odors, such as from sweat, and in the use of natural perfumes. For land animals we know about their release in urine to mark territory and to attract a mate of opposite sex. Insects are widely cited, such as in their use of pheromones to mark their trails -- particularly noted for this are ants.
Pheromones are found to be in aquatic animals as well, including extensively in fishes. It is known by scientists, and from their published literature, that pheromones are commonly used by fishes in their communication. In other words it is one of the ways that they "talk" to each other, besides in their body movements. There is copious scientific literature on this subject for fishes, including back to 1941 when Karl von Fritsch termed one type of fish pheromone as "Schreckstoff" (fright stuff), which are injury-released or chemical-alarm pheromones (see Christopher Bosio "Alarm Pheromones in Fish: Functional and Evolutionary Aspects" 1994 http://www.colostate.edu/Depts/Entomology/courses/en570/papers_1994/bosio.html ). It has been observed in injured fishes, in their giving off of an alarm signal to other fishes to flee (particularly recognized by conspecifics), apparently in hormone-like chemical form released from their skin and open wounds.
Fishes also produce pheromones in their gonads through the seminal fluid in males and ovulation in females, and in their rectal organs. One of the researched areas is in female fishes full of eggs releasing pheromones into the water to attract males. Fishes are sensing the pheromones through the vomeronasal organs in their highly sensitive nostrils.
The chemicals involved in fish pheromones cover a wide range of forms, including steroids such as androstenedione, and polyamines as olfactory stimulants. Among the fishes best known for their pheromones and their effects on their behavior are goldfish Carrassius auratus (see www.life.umd.edu/grad/MLfsc/res/Pheromones.ppt). A search of the Internet and elsewhere will provide many references to pheromones in fishes used in aquarium keeping, including on zebra fishes, cichlids, gobies, poeciliids, sticklebacks, minnows, carp (koi), etc. There are also references to "sex steroids" in coral spawning, based on research on scleractinian corals http://www.bioone.org/perlserv/?request=get-abstract&issn=0006-3363&volume=068&issue=06&page=2255.
One of the foremost researchers on fish pheromones is Peter W. Sorensen of the University of Minnesota. A recent review by him and Norm E. Stacey is "Brief review of fish pheromones and discussion of their possible uses in the control of non-indigenous teleost fishes," New Zealand Journal of Marine and Freshwater Research, 2004, vol. 38, pp. 399-417 http://www.rsnz.org/publish/nzjmfr/2004/036.php.
In crowded aquariums and ponds, and in shipping fishes and invertebrates, the use of Kordon's product Amquel+® has provided unexpected further insights into fishes' body odors, because of the process whereby AmQuel+ detoxifies nitrogen compounds in the water, such as ammonia/ammonium, nitrites, and nitrates. It apparently also eliminates pheromones in the form of amines and other nitrogen compounds. At this time it is not known to what extent the various kinds of pheromones are removed by AmQuel+, but indications are it is removing those that are toxic when the pheromones become concentrated in the water.
 It has been found that AmQuel+'s ability to remove fishes' pheromones in the water can be of significant importance for improving fish health and survivability. In the confines of aquarium or pond conditions pheromones can build up to excessive levels, as fishes and other organisms in the water are "talking" to each other. While what is known about the extent and nature of pheromones in fishes and other aquatic life in aquarium and pond keeping is still limited -- what has been observed is that the use of AmQuel+ in fish keeping eliminates some or all pheromones released in the water that can be of harm, thereby increasing fish survivability and growth rates when the excess toxic pheromones are removed.
What particularly brought the presence of pheromones to our attention was in shipping and raising fishes, when fishes are confined together in limited spaces. For example, larger marine plectognath fishes (Ostraciid cow and box fishes, Monacanthid file fishes, Tetraodontid puffer fishes, Balistid trigger fishes) can be particularly troublesome in shipping, tending to harm each other (and themselves) severely during shipment by aggressively releasing potent odors. (Presently one of the ways that shippers use to avoid the pheromone problem with plectognath fishes is mainly to ship younger fishes that are less likely to have toxic pheromones.)
The fishes may intend merely to establish territoriality and to repel each other by the use of their pheromones. In the confines of shipping bags in which the pheromones cannot be dissipated, this can lead to the fishes killing themselves and others during shipment. It is interesting to note that when these fishes are shipped one to a bag, the survival rate is improved. This is particularly noted for coral reef fishes which are more difficult to ship successfully, and are suspected of having more toxic pheromones. Also observed was that in raising certain kinds of fishes, particularly cichlids, such as angel fishes (Pterophyllum scalare=eimekei), growth rates can vary greatly between individuals. The more aggressive fishes seem to be those that are the largest, and who appear to be suppressing growth of others with their pheromones.
When a Kordon AmQuel product (particularly the more potent AmQuel+) is used, survival rate is much higher, because of the ability of these chemicals to detoxify the pheromones. The growth rates for all of the fishes affected by pheromones are moderately increased. It can be seen that the growth rates are more even among these fishes, as the result of regularly using an AmQuel product. In general this is indicating that pheromones released by the more aggressive fishes are inhibiting the growth rate of other fishes.
What was also learned from the use of AmQuel+ is that not all aquarium and pond fishes have such toxic pheromones, so that pheromones are not as great a factor in their growth rate or aggressiveness. In general, toxic pheromones are not found in aquarium keeping to be as much of a factor for schooling fishes, aquatic invertebrates, many nonaggressive fishes, and in pond fishes such as koi and goldfish. However, it seems that in belligerent fishes, toxic pheromones can be a serious factor. Also, it has to be kept in mind that much needs to be learned about this subject. For example, for most aquatic invertebrates the importance of their release of pheromones has yet to be discovered.
Considering the confines of space in shipping fishes and aquatic invertebrates -- particularly for shipping larger sized aquatics -- Kordon's AmQuel+ is recommended to be used to eliminate pheromone toxicity in the water to be certain that any toxic pheromones released by the fishes are eliminated. (See Kordon Article "New Methods For Commercial Shipping of Aquarium Fishes and Aquatic Invertebrates".) AmQuel+ also is helpful by detoxifying the nitrogen compounds in the excretion of the fishes and aquatic invertebrates. When used in shipping fishes and other aquatics, the use of AmQuel+ can make a significant difference in stress and survival rates during shipping.
Also, It is recommended that AmQuel+ be used regularly in community aquariums, including in new aquariums when the fishes are getting acquainted and are establishing their hierarchies and territories. This involves an increased use by them of their pheromones. As the concentration of pheromones in the aquarium builds up, this can be an adverse stress and survival factor, for which AmQuel+ provides a solution. Pheromones are further discussed in the Kordon Article "What the Beginning and Advancing Aquarist Absolutely Needs to Know and Do When Starting an Aquarium".
What has not been discussed is the potential for the use of Kordon's AmQuel+ in the shipping of live fish and other aquatic animals in commercial aquaculture of food fish and invertebrates, a use that has not yet been developed.
A helpful overview for aquarists on the olfactory organs of fishes and a list of general references is provided by Mark E. Evans in his review article in the Advanced Aquarist's Online Magazine vol VI, May 2007, "Aquarium Fish: Smell You Later: Olfaction in Aquarium Fishes" http://www.advancedaquarist.com/2007/5/fish wherein is discussed "the inner workings of a fish's sense of smell."
Evans' list of References:
- Gratzek, John B. (Editor); Aquariology: The Science of Fish Health Management; Tetra Press Publication, 1992
- Love, R. Malcolm; The Chemical Biology of Fishes; Academic Press, 1970
- Moyle, Peter B. and Cech Jr., Joseph J.; Fishes: An Introduction to Ichthyology; Prentice-Hall Inc., 2000
- Reebs, Stephen; Fish Behavior In The Aquarium And In The Wild; Cornell University Press, 2001
- Zupanc, Gunther K. H.; Fish And Their Behavior; Tetra Press, 1985
- Stoskopf, Michael K.; Fish Medicine; W. B. Saunders Company, 1993
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