Fishes and birds kept for leisure


Many kinds of animals, including fishes, are harmed significantly as a consequence of being kept by humans as display items, for companionship, or to satisfy desires to create collections. Fishes suffer harms when they are kept in tanks, and fishes who are not born into captivity suffer additional harm from capture and relocation to the tank environment. These harms occur as a consequence of the fact that fishes are used as living ornaments because they are esthetically pleasing, stimulating, or more relaxing, while the interests of the fishes are barely taken into account.

The capture of fishes for use as ornaments

Between 20 and 24 millions of fishes are captured from the wild every year. Moreover between 9 and 10 millions of other aquatic animals, such as molluscs and shrimps, are captured every year.1

Though “aquariums” may sound like a benign name, for the animals that live in them they are tanks that confine and frustrate them. Additionally, a common method of capturing fishes for display involves spraying a sodium cyanide mixture into areas in the wild where the fishes are living. The chemical stuns the animals and renders them immobile so that they can be captured easily. Using such poisons harms not only the fishes targeted for capture, but also other sentient beings living in the same areas. It has been estimated that between 70-90% of the fishes captured from the Philippines for display are caught using this fishing method. In fishes as in humans, cyanide poison prevents the transport of oxygen to the cells and results in a condition similar to carbon monoxide poisoning.

Fishes living in tropical marine areas who are captured using the sodium cyanide poisoning technique suffer very high mortality rates for several weeks after their capture.2 It has been shown recently that the shock and stress suffered by fishes due to the use of cyanide poisons results in mortality rates as high as 75% in the first two days after being captured. Because their mortality rate is so high, even greater numbers of fishes are captured to try to meet the lucrative demand for them.

Harm suffered by fishes as a consequence of translocation

Many of the fishes who survived the sodium cyanide poisoning die during transport to their intended destinations. It has been estimated that up to two thirds of the coral fishes captured for display in aquaria die during the translocation. Many die due to the shock and stress of being captured and transported, and many die due to the harsh physical conditions they are subjected to during transport (often they are just packed and carried in plastic bags). A 5-10% mortality rate is estimated to occur during translocations and at holding facilities.3 During the acclimatization period following arrival at the destination, the mortality rate rises, with an additional 30% dying during this part of the process.4

Harm suffered by fishes kept for display

The harm suffered by fishes used for display are not limited to suffering and death during capture and translocation. The standard conditions that fishes endure in the tanks where they live are also quite harmful. Some of the harms that come to fishes in the tank environment are described below.

Consequences of selective breeding. Many fishes are chosen for breeding according to the way they look, behave, or serve other human purposes, even if this means they are likely to suffer from congenital issues.

Inappropriate temperature. Tanks and pools often have water temperatures that are too cold or too warm for their inhabitants. This does not promote good health or comfort; it can also cause significant suffering and lead to premature death. There is a difference between the temperature levels at which animals can survive and the one at which they can feel comfortable. And, although ignorance about water temperature settings may be part of the reason for incorrect settings, other factors such as saving money or putting incompatible fish in the same tank also contribute to the problem.

Poor water quality. Poor water quality is probably the most common cause of death in fishes who are used as ornaments for display. It often occurs with people who have fish tanks at home and don’t know a lot about the needs of the animals, such as their need for water that is adequately oxygenated and filtered.

Inappropriate diets. The wrong diets are often fed to animals kept by people who don’t know about their nutritional requirements. Even when fishes living without proper nutrition aren’t killed by it, a deficiency in diet can be a cause of considerable chronic and/or acute suffering.

Uncomfortable habitats. In order to feel safe and comfortable, some fishes need to have certain elements around them such as rocks, corals, and algae, or things that can function similarly, especially when they are being kept in an aquarium with other incompatible animals from whom they would like to hide.

Crowded conditions. Fishes living in crowded conditions may suffer from acute stress, as can be evidenced by their raised cortisol levels. They can also have depressed immunity and become more susceptible to other damaging effects of stress.

Aggression among crowded fishes may cause injury, especially in situations where there is strong competition for food, as has been observed in fishes living in fish farms.5 In such situations fishes can be prevented from eating, can grow poorly, and can become more susceptible to disease.

Stressful social situations. Another source of stress to fishes involves the social environment and applies both to those who live in schools and those that do not. Social contact or the lack thereof, depending upon the animal’s natural tendencies, can cause suffering and poor health.

Predators and prey. It has been estimated that in up to 19% of ornamental tanks predator and prey were kept together.6 Even brief exposure to a predator causes signs of severe stress such as increased cortisol levels, increased respiration rates and suppressed feeding.7

Dyeing and mutilating. Dyeing fishes with color has become a common practice among those who display fishes. Glassfishes in particular are injected with fluorescent dyes.8 This can be harmful to their health, leading in many cases to disease, often ending in the premature death of the animals.9 Sometimes fishes are inflicted with piercings or tattoos for financial or esthetic reasons and are caused great suffering by the mutilations.


Keeping birds for companionship and ornamentation is a common practice, known as aviculture. Breeding birds can harm them in addition to the harms of living in captivity. The reasons people keep birds captive are varied; they may simply enjoy having the birds around for how they look or behave, they may enjoy collecting them out of curiosity, or they may breed birds for financial gain. In some countries birds are not bred but are captured and then transported elsewhere.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) forbids the sale of some species. However, this protection is only due to conservationist reasons to conserve the species; it is not due to concern for the individual animals themselves. CITES also covers only a certain number of animals. Others are left unprotected once conservation needs are met. Moreover, this convention doesn’t save the animals it supposedly protects from being harmed in any way that does not hamper the conservation of the species they belong to.

Under CITES, while it is illegal to capture some birds for purposes of trade, it is still perfectly legal to do so with many others.

How birds suffer as a consequence of confinement

Regardless of whether they are captured or bred in captivity, birds who are kept in cages usually suffer. They commonly lack enough space to have a normal life. Many suffer from significant boredom and stress. Sometimes caged birds can be observed singing, and although some people believe that the fact that they are singing shows that they are happy, it may not be true. Birds can sing for several reasons, such as to make other birds aware of their presence so they don’t enter their territory, or because they are looking for a mate, which are unrelated to whether they are feeling happy or not. Most birds lack even the basic grooming facilities that they would need to feel comfortable in a captive environment, such as permanent access to water or dust for bathing, and this can result in great stress. Even those with some room can suffer boredom and frustration for much of the time. The frustration is usually shown through abnormal behavior as the birds try to cope with their circumstances.10 Furthermore, birds who are bored can exhibit destructive behaviors, including self-destructive ones. Some behavior can start out as innocuous coping strategies, such as minor feather plucking to try to relieve their general state of itchiness. However, these behaviors can develop into life-threatening obsessions as they try to cope with the continual stresses of their lives.

In some cases birds have identification rings put on them. For some individuals these rings are a great source of stress, so much so that in their attempts to remove these rings they end up mutilating themselves. All this stress can lead to other health issues as well.

Many captive birds suffer because their ambient temperature is not suitable. They can also suffer when their diet is either unpalatable or nutritionally insufficient.11 Various health problems may result from the wrong diet.12

Bird diseases

The situations in which captive birds are forced to live makes them very susceptible to a wide range of diseases.13

  • Psittacosis (parrot fever) is a form of the Chlamydia bacterium that can affect all hookbills. It is highly contagious and can be passed on to other kinds of animals also. The symptoms can include feather loss, abnormal feather development, absence of powder down, and growths, lesions and abnormalities of the beak.
  • Polyomavirus causes flight feathers and tail feathers to develop abnormally, or not to develop at all. The symptoms can include loss of appetite, enlarged abdomen, paralysis, and diarrhea. Some birds may be carriers of the virus without showing symptoms; when they are stressed and they shed as a result, other birds can be infected.14
  • Candida or candidiasis infections involve the overgrowth of yeasts that are usually found in the digestive system. Symptoms can include white lesions in the mouth and throat, vomiting, loss of appetite, and a crop that empties slowly.
  • Proventricular dilatation disease is a disease which causes weight loss, vomiting, swollen crop, and changes in droppings.
  • Parasites, such as aspergillosis, giardia, roundworms, and Sarcocystis also cause suffering to captive birds.

Further readings

Duncan, I. J. H. & Hawkins, P. (eds.) (2010) Welfare of domestic fowl and other captive birds, Dordrecht: Springer.

Gollerstein, G. A. (1994) The complete bird owner’s handbook, New York: Howell.

Graham, D. L. (1998) “Pet birds: Historical and modern perspectives on the keeper and the kept”, Journal of the American Veterinary Medical Association, 212, pp. 1216-1219.

Halim, A. (2002) “Adoption of cyanide fishing practice in Indonesia”, Ocean & Coastal Management, 45, pp. 313-323.

Indrawan, M. (1999) “Live reef food fish trade in the Banggai Islands (Sulawesi, Indonesia): A case study”, SPC Live Reef Fish Trade Information Bulletin, 6, pp. 7-14.

Lima, S. L. (1998) “Predator induced stress and behaviour”, Advances in the Study of Behaviour, 27, pp. 215-290.

McAllister, D. E.; Caho, N. L. & Shih, C. T. (1999) “Cyanide fisheries: Where did they start?”, SPC Live Reef Fish Information Bulletin, 5, pp. 18-21.

Metcalfe, N. B. & Thomson, B. C. (1995) “Fish recognize and prefer to shoal with poor competitors”, Proceedings of the Royal Society B, 259, pp. 207-210.

Moberg, G. P. (1999) “When does an animal become stressed?”, Laboratory Animals, 23, pp. 22-26.

Pet, J. S. & Pet-Soede, L. (1999) “A note on cyanide fishing in Indonesia”, SPC Live Reef Fish Information Bulletin, 5, pp. 21-22.

Reavill, D. R. (2004) “Tumors of pet birds”, Veterinary Clinics of North America: Exotic Animal Practice, 7, pp. 537-560.

Reimchen, T. E. (1994) “Predators and morphological behaviour in the threespine stickleback”, in Bell, M. A. & Foster, S. A. (eds.) The evolutionary biology of the threespine stickleback, Oxford: Oxford University Press, pp. 207-240.

Startup, C. M. (1970) “The diseases of cage and aviary birds (excluding the specific diseases of the budgerigar)”, in Rogers, A. & Norris, K. A. (eds.) Encyclopedia of aviculture, I, London: Blandford, pp. 46-58.

Tsai, S. S.; Park, J. H.; Hirai, K. & Itakura C. (1993) “Eye lesions in pet birds”, Avian Pathology, 22, pp. 95-112.

Vriends, M. M. (1987) Aviaries: A complete introduction, Neptune City: TFH Publications.

Wendelaar Bonga, S. E. (1997) “The stress response in fish”, Physiological Reviews, 77, pp. 591-625.

Wolf, P. & Kamphues, J. (2003) “Hand rearing of pet birds – Feeds, techniques and recommendations”, Journal of Animal Physiology and Animal Nutrition, 87, pp. 122-128.


1 Wabnitz, C.; Taylor, M.; Green, E. & Razak, T. (2003) From ocean to aquarium, Cambridge: UNEP World Conservation Monitoring Centre, pp. 6-7.

2 Hignette, M. (1984) “Utilisation du cyanure pour la capture des poissons tropicaux marins destinés a l’aquariologie: Methodes de diagnostic”, Oceanis, 10, pp. 585-591.

3 Ferraz de Oliveria, E. (1995) Studies on parasites of ornamental fish from South America with potential for transfaunation, PhD Thesis, Stirling: University of Stirling [accessed on 30 April 2020].

4 FitzGibbon, D. (1993) “UK restriction proposals”, Ornamental Fish International Journal, 10, pp. 12-14.

5 This has been studied in particular for its relevance in fish farms: Greaves, K. & Tuene, S. (2001) “The form and context of aggressive behaviour in farmed Atlantic halibut (Hippoglossus hippoglossus L.)”, Aquaculture, 193, pp. 139-147; Carter, C. G.; Purser, G. J.; Houlihan, D. F. & Thomas, P. (1996) “The effect of decreased ration on feeding hierarchies in groups of greenback flounder Rhombosolea tapirina: Teleostei)”, Journal of the Marine Biological Association of the United Kingdom, 76, pp. 505-516.

6 Czányi, V. & Dóka, A. (1993) “Learning interactions between prey and predator fish”, Marine Behaviour and Physiology, 23, pp. 63-78.

7 Metcalfe, N. B.; Huntingford, F. A. & Thorpe, J. E. (1987) “The influence of predation risk on the feeding motivation and foraging strategy of juvenile Atlantic salmon”, Animal Behaviour, 35, pp. 901-911.

8 MacMahon, S. & Burgess, P. (2007) “Why it’s cruel to dye”, Practical Fishkeeping, 22 April.

9 Sharpe, S. (2014) “Artificially colored aquarium fish: Death by dyeing”, Freshwater Aquariums –, November 24 [accessed on 9 January 2016].

10 Hollmann P. (1997) “Behavioral disorders in psittacines. 2: Therapeutic measures”, Tierarztliche Praxis, 25, pp. 356-362. Van Hoek, C. S. & ten Cate, C. (1998) “Abnormal behavior in caged birds kept as pets”, Journal of Applied Animal Welfare Science, 1, pp. 51-64.

11 See for instance regarding nutrition problems Wolf, P.; Bayer, G.; Wendler, C. & Kamphues, J. (2009) “Mineral deficiency in pet birds”, Journal of Animal Physiology and Animal Nutrition, 80, pp. 140-146.

12 Wallach, J. D. (1970) “Nutritional diseases of exotic animals”, Journal of the American Veterinary Medical Association, 157, pp. 583-599.

13 Patrak, M. L. (ed.) (1996 [1969]) Diseases of cage and aviary birds, 3rd ed., Philadelphia: Lea and Febiger.

14 Gerlach, H. (1984) “Virus disease in pet birds”, Veterinary Clinics of North America: Small Animal Practice, 14, pp. 299-316.