Ethical and Ecological Implications of Keeping Fish in Captivity

Fish tanks are ubiquitous—found in doctor’s offices, Chinese restaurants, corporate headquarters, and in millions of homes throughout the world. Some studies report that they reduce anxiety, stress, and blood pressure, calm hyperactive children, and provide some relief for those suffering from Alzheimer’s disease. They can be big or small, plain or fancy, and they come in every conceivable configuration. There’s even a reality television show, “Tanked,” that builds them for the famous and well-heeled.

Whether a small, sterile bowl with a single forlorn fish sitting on a kitchen table or a large tank in a municipal aquarium, they are designed to keep fish in captivity for human enjoyment. Within their walls, a cornucopia of freshwater and marine species can be found that, like their tanks, come in a variety of colors, shapes, and sizes. Many are bred in captivity while others are captured in the wild and traded internationally.

But what are the consequences of captivity? Beyond the size of the tank, number of fish, and water quality and temperature, there are ethical and environmental costs inherent to the ornamental fish trade. Sadly, most captive fish live short lives and are easily replaced with new “stock”— creating a constant demand that feeds a cycle of collection/production, acquisition, and death.

In recent years, the film Blackfish has advanced the global effort questioning the ethics of keeping orcas in captivity. It has challenged people to recognize the cruelty of keeping large, intelligent, and sentient animals in such small tanks. While ornamental fish don’t travel the same distances as wild orcas, they are sentient—showing far more cognitive abilities than they are given credit for—and few, if any, spend their entire lives in the wild in the volume of water contained in a standard fish tank.

Remarkably, tanks that contain no more than one-half gallon of water—a size insufficient to provide a home to even the smallest ornamental fish species—continue to be sold. Bed Bath and Beyond, one of many stores that sell tiny 6-inch, half-gallon cube tanks, brags that “they take up very little space and look great on counters, desks, podiums or even mounted on a wall” and their “chic design … blends in nicely in a variety of household or office settings and is a simple way to introduce a calming element to your everyday environment.”

Even a larger, full-size home aquarium can’t provide the diversity of habitats and conditions that are found in the wild, and fail to meet the physical and psychological needs of its captives. Often, according to various aquarium publications, these tanks are overstocked with fish living in poor quality water, resulting in suffering and premature death. Moreover, while “tiny tanks” are preferred by some, aquarium enthusiasts report that they are more difficult to properly maintain than larger tanks—contributing to high death rates for fish relegated to a life in a few cups of water.

While most do not question the sentience and intelligence of dogs, cats, and many other animals, these traits are not often attributed to fish. Scientists continue to debate whether fish experience pain as humans do, but Dr. Culum Brown of Australia’s Macquarie University, in a 2015 paper in Animal Cognition, concluded that, “fish perception and cognitive abilities often match or exceed other vertebrates,” and that “the extensive evidence of fish behavioural and cognitive sophistication and pain perception suggests that best practice would be to lend fish the same level of protection as any other vertebrate.”

Beyond ethical concerns, the ecological implications of the hobby and the industry that feeds it are enormous. According to the literature, while 95 percent of freshwater fish are bred in captivity, 95 to 99 percent of marine (or saltwater) fish in the aquarium trade are collected from the wild. Globally, it is estimated that over 1 billion ornamental fish (freshwater and marine) from some 5,400 species are traded annually for the aquarium industry. This does not include the invertebrates, crustaceans, live rock, corals, and plants that are also part of the ornamental fish trade.

The United States is the number one importer of ornamental fish, followed by the European Union and Japan. The majority of captive-produced freshwater fish come from Southeast Asia and Florida, while most marine fish are exported by Indonesia, the Philippines, Malaysia, Vietnam, Brazil, the Maldives, Papua New Guinea, Sri Lanka, the Solomon Islands, and Timor-Leste. In the United States alone, according to a detailed examination of import invoices undertaken by Dr. Andrew Rhyne and colleagues, 10.5 million fish from over 1,800 species were imported into the country in 2004–2005. For comparison, at least 10 million ornamental fish were imported into and 1.3 million exported from the United States in 2014, with over 83 percent of these fish caught in the wild. Yet, this understates the number of fish in the US aquarium trade, as it doesn’t include fish traded domestically.

Unfortunately, credible, long-term studies assessing the impact of the ornamental fish trade on most wild-caught freshwater and marine species in trade are sparse. This makes it difficult to fully analyze the biological and ecological impact of trade, particularly in light of other natural and anthropogenic threats to these species and their habitats. Even obtaining accurate species-specific global trade data is nearly impossible. The United Nations collects such data, but all species are combined and trade is reported in kilograms, not in number of fish.

For ornamental fish, particularly those from the wild in high demand, the biological and ecological consequences of the trade can be devastating, resulting in localized species depletion and extinction. Fish endemic to a particular area and those with life history characteristics making them slow to respond to population perturbations are particularly at risk.

Other impacts from the trade include destructive fishing practices and the significant capture-to-tank mortality of many species. The use of toxins like cyanide to capture fish can kill or impair both target and nontarget species, while also killing coral or impairing its ability to provide shelter or food to marine life. Although the industry has established guidelines to try to eliminate such practices, reportedly such poisons continue to be widely used. In addition, some collectors physically destroy coral to capture target fish.

If the fish don’t die during collection, a large number die in captivity both before and after they are sold to hobbyists. Depending on the source of the fish, many wild-caught animals spend days or weeks in transit before arriving at your local pet store; mortality rates from stress, injury, disease, or mistreatment can exceed 80 percent. While industry guidelines are intended to reduce capture-to-sale mortality, it is unclear how many traders are complying with the standards, or if they are effective.

For those fish that do survive, some are intentionally or accidentally released into the wild. In some cases, these species can become invasive and adversely impact local ecosystems by outcompeting native fish, disrupting predator-prey dynamics, and transmitting diseases. An analysis by Drs. Whittington and Chong of the disease-transmission potential of the ornamental fish trade in Australia revealed a number of diseases in imported fish that had cleared quarantine, as well as the presence of nonnative fish and their introduced diseases in the wild. The same impacts have been documented in other countries, including the United States, which has no known quarantine process for imported ornamental fish. Imported lionfish, for example, have been dumped into the wild by home aquarium owners for the past 25 years, and have become an enormous ecological threat to Atlantic coastal waters in the United States and the Caribbean.

Freshwater species tend to be easier to maintain in captivity, generally have lower mortality rates and, since most are captive bred, don’t pose as great a risk to wild fish stocks. Nevertheless, they too suffer in captivity and the conservation implications of their trade are not benign. The International Union for Conservation of Nature issued a report in 2003 indicating that a large number of freshwater fish are collected from the wild, particularly in Brazil, Colombia, Indonesia, Peru, and East African countries. For these species, overcollection can result in localized depletions and extinctions, capture-to-tank mortality can be high, and they also can become invasive species if released.

Despite the massive trade in fish for aquariums, there are very few aquarium species protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Given the quantity of fish in trade, evidence of overcollection impacts, and lack of credible information about the impact of trade (and other threats) on many species, CITES protections may be warranted. Without international restrictions on trade, the fate of thousands of fish species is controlled by national laws which, in many countries, are woefully inadequate.

Ultimately, the consumer has to decide whether to keep fish in captivity. While many people around the world rely on the ornamental fish trade for all or some of their income, is this worth the ecological and ethical costs of captivity? Perhaps if you are considering a fish tank for your home, you should think like a fish and ask if you would prefer a life in the wild or behind glass walls.

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