catching nemo

The Impact of Catching “Dory” on Coral Reefs

A scientific study conducted in the spring of 2016 warns that the popularity of animated movies like “Finding Nemo” and its sequel, “Finding Dory,” may harm the coral reefs they portray so brilliantly. The demand for the types of fish depicted in the movies has led to an increase in the number of clownfish and blue tangs being sold as pets. While clownfish have been successfully bred in captivity, blue tangs have not. That means all of the pet blue tangs will be wild-caught – and a very common method for catching tropical fish is stunning them with cyanide. While cyanide fishing is an easy way to catch fish, the toxin is harmful to both the fish and the coral reef ecosystem.

What is Cyanide Fishing?

Cyanide fishing began in the 1960s, when divers in the Philippines began using it as a way to catch fish for the pet trade. Over time, it became a common method of catching live fish in many countries in Southeast Asia – despite being illegal in many of them. Most of the 11 million tropical fish sold in the US come from the Indo-Pacific coral reefs, where cyanide fishing is distressingly common. The National Oceanic and Atmospheric Administration released a report in 2008 estimating that 90 percent of the coral reef fish sold in the US were captured through illegal methods like cyanide fishing.

Quick Facts:

  • The aquarium fish market is now worth over $200 million a year.
  • Cyanide has also been used to capture larger reef fish which are sold to specialty restaurants in some Asian countries that have large Chinese populations.

Craig Downs, the director of the Haereticus Environmental Laboratory in Clifford, Virginia, described cyanide fishing as a “cheap and easy” way to catch fish. The fisher crushes a cyanide tablet and mixes it with water in a squirt bottle. They then squirt some cyanide onto a fish and stun it. A person trying to catch a large group of fish can pump cyanide into the water from their boat and thus stun dozens or hundreds of fish at once. Scientists have confirmed that cyanide is poisonous to coral as well as to the fish. Divers cause even more damage to the coral reef ecosystem by prying or hammering apart coral to retrieve fish that have fled into the crevices.

The cyanide fishing impact on both fish and their environment is devastating. Many fish die within three weeks of being exposed, often after they’ve already been sold.

Quick Facts:

  • 30 million fish are captured through cyanide fishing every year.
  • Roughly 27 million of the captured fish die from exposure to the cyanide.

According to researchers, fishers have squirted over a million kilograms of cyanide onto coral reefs in the Philippines alone since the 1960s. As fish populations decline, fishers move to other reefs. In fact, cyanide fishing impact has spread even further, for the practice is suspected or has been confirmed in regions ranging from eastern Africa to the central Pacific.

The Study

Downs and Rene Umberger, the director of the conservation group For the Fishes, conducted a study to estimate the number of fish that had been exposed to cyanide. Unfortunately, the average aquarist cannot spot the signs of cyanide poisoning in their pets; it takes a fish pathologist to do that. A fish that has been exposed to cyanide will eventually convert it into another chemical called thiocyanate, which is then excreted in the fish’s urine.

Downs and Umberger bought 89 fish from pet stores in Virginia, North Carolina, Maryland, Hawaii, and California. They took samples of the water in their tanks and sent them to an independent laboratory. The lab results showed that over 50 percent of the fish had been exposed to cyanide. Even higher percentages of the Green Chromis and blue tangs studied showed signs of cyanide exposure.

The two researchers also obtained some fish that had been bred in captivity and collected samples of their tank water. The results from the laboratory came back negative; none of the captive-bred fish had been exposed to cyanide.


Downs points out aquarists don’t have to give up keeping pretty tropical fish; they just have to choose their fish more wisely. In other words, they have to buy captive-bred fish that are not exposed to cyanide or otherwise stressed by being taken from the wild.

Unfortunately, only about 40 percent of the 1800 fish species sold to private aquaria in the US are captive-bred. For the Fishes has created a free app called Tank Watch that can be used with Apple devices. Tank Watch provides a list of all of the captive-bred species; if a fish isn’t on that list, consumers may assume that it was wild-caught through cyanide fishing or some other hurtful and possibly illegal method. Tank Watch also lists fish that are usually taken from the wild, and it provides a list of easy-to-care-for fish for beginners.

The World Resources Institute, the International Marinelife Alliance, and several organizations have established a program in Indonesia that attacks the problem of cyanide fishing from the supplier’s end. They are educating fishers in more sustainable and environmentally friendly methods to catch fish for the aquarium trade.