Unsustainable Harvests

2018 has been designated the 3rd International Year of the Reef – IYOR2018.  This week, Dr. Farahnaz Solomon, Marine Biologist and IYORTT team member looks at one of the major services provided by coral reefs fisheries and laments the destructive and wasteful methods used to harvest wild fish. 

Coral reefs are found worldwide in tropical oceans. They cover an area of about 284, 300 km2 around the shores of over 100 countries (Photo 1). Overlaying a human population map with a coral reef distribution map shows that 10% of the world’s population live within 100 km of coral reefs. Excluding the reasonably wealthy developing countries, 75 percent of these individuals (>400 million) are from the poorest developing countries. Most live in rural environments and are likely to be dependent on reef resources to support their livelihoods and for food security.

Photo 1: Global Distribution of Coral Reefs.  Source: NOAA

Due to their nearshore locations in relatively shallow waters, many reefs are easily accessible without the need for boats or specialized equipment. Little investment is needed to enter the fishery, making it a feasible option for individuals with limited financial resources. As of 2013, the number of coral reef fishers worldwide was estimated at 6.1 million. 58 % of these fishers are concentrated in the Philippines, Indonesia and India (Teh et al., 2013). On a global scale, coral reef fisheries have been valued at about US$6.8 billion/yr (Burke, 2011).  These fisheries are intensely targeted not only for a local source of protein, but also for export trades such as the “Live Reef Food Fish” (LRFF), aquarium, and curio trades. Additionally, not only fish are extracted from coral reefs but also invertebrates such as crabs, sea cucumbers and sea urchins, and corals themselves.  In the Caribbean, the Spiny Lobster (Panulirus argus) is the primary fishery for many countries contributing significantly to the export income for the region.

Overall, there is high fishing pressure on coral reefs in most areas where they occur. More than 55% of the world’s coral reefs are considered threatened, and almost 30% highly threatened by overfishing and/or destructive fishing. Two of the most destructive fishing methods used on reefs are cyanide fishing and dynamite fishing. Cyanide fishing which is used to capture live fish is fueled by the international aquarium trade and the “Live Reef Food Fish Trade” (LRFFT) which is centered in Hong Kong.  Fishers dissolve cyanide tablets in seawater and squirt it from a bottle towards targeted fish on top of coral heads (Photo 2). Cyanide which is a highly toxic chemical stuns the fish without killing them, making them easy to catch (Photo 3). The Philippines, Sri Lanka and Indonesia have all banned cyanide fishing, yet it still occurs due to the lack of adequate law enforcement. The incentive is great as fishermen get as much as five times more money for live fish than for dead fish. Globally, the marine aquarium trade is estimated to be worth about $200 million per year. Up to 90 percent of the 11 million tropical fish that enter the US each year are caught illegally with cyanide.

Photo 2: A fisher using cyanide to hunt for fish.  Source: http://www.saveourseafood.my/about/ocean-issues/
Photo 3: Fisherman collecting stunned fish after being poisoned.
Source: http://www.saveourseafood.my/about/ocean-issues/

In the LRFFT, fish selected and taken alive from the aquarium tank of a restaurant can fetch up to 300 dollars a dish (Photo 4). Unfortunately, some of the fish caught on coral reefs are the most valued in this trade – these include groupers and wrasses. Among them are the endangered humphead wrasse (Photo 5). The main markets for LRFF are Hong Kong and mainland China with smaller markets in Malaysia and Singapore. Due to depleted local stocks and increased market demand, Hong Kong relies almost completely on imported seafood. Much of this live seafood comes from countries in Southeast Asia where cyanide fishing is still the method of choice. 

Photo 4: Life reef fish sold at Hong Kong restaurants. Source: Professor Yvonne Sadovy

So, what are the impacts of cyanide on reef life? Well, if it does not kill the fish, it temporarily impairs its ability to swim and breathe. Some fish may get too much exposure and die then and there, others die while being transported to their destination. What is even worse is that not only fish are affected but also coral. Each live fish caught with cyanide kills about a square yard of coral. Stunned fish often end up in hidden clefts and so the fishermen have to use hammers to break up pieces of coral. Dynamite is also used on reefs to break up coral blocks and rouse fish.  Once the corals are dead, the entire ecosystem collapses. Without coral, reef fish, crustaceans, plants, and other animals no longer have food, shelter, and breeding grounds. 

Photo 5: The endangered humphead wrasse is exploited in the LFFRT Source: https://www.aqua.org/Experience/Animal-Index/humphead-wrasse

Dynamite fishing also known as blast fishing is the use of explosives to stun or kill schools of fish for easy collection. This type of fishing destroys the coral reef habitat, reducing it to rubble. It is an extremely wasteful method:  it kills all organisms within a 20m radius however only three percent of those organisms can be collected and sold. Dynamite fishing is one of the leading causes of reef destruction in Southeast Asia over the past 20 years or so. Unfortunately, many fishermen still feel that this is the only way to collect sufficient food to support their families.

Here in the Caribbean, overfishing has led to the decline of parrotfish – one of the keystone species on our reefs. The transformation of many Caribbean reefs to algal dominated habitats in recent decades have been linked to the decline of this herbivorous fish. Results of a recent study showed that there is indeed a strong correlation between parrotfish abundance and coral reef growth historically – coral reefs grew faster and healthier when parrotfish was abundant (Cramer et al., 2017).  

In addition to overfishing and destructive fishing methods, coral reefs are stressed by climate change events as well as land-based development and pollution. The combined impact of multiple stressors may compromise the ability of coral reefs to continue supporting the food and income needs of coastal communities in the future. Decisions have to be made to balance protecting coral reefs and allowing people to use them for social and economic purposes.


Bale, R. 2018. The horrific way fish are caught for your aquarium – with cyanide. https://news.nationalgeographic.com/2016/03/160310-aquarium-saltwater-tropical-fish-cyanide-coral-reefs/ Accessed online July 1st 2018

Burke, L., K. Reytar, M. Spalding, and A. Perry. 2011. Reefs at Risk Revisited. Washington, D.C., World Resources Institute (WRI), The Nature Conservancy, WorldFish Center, International Coral Reef Action Network, UNEP World Conservation Monitoring Centre and Global Coral Reef Monitoring Network, 114p

Cramer, K. L. et al. 2017. Prehistorical and historical declines in Caribbean coral reef accretion rates driven by loss of parrotfish. Nature Communications 8, 14160 doi: 10.1038/ncomms14160.  Accessed online July 1st 2018

Donner, S.D. and Potere, D. 2007.The Inequity of the Global Threat to Coral Reefs. BioScience 57(3):214-215. Accessed online July 1st 2018

Science Daily, 2018. New study sheds light on the dark side of Hong Kong's most lucrative seafood trade. https://www.sciencedaily.com/releases/2018/02/180205102732.htm   Accessed online July 1st 2018

Coral Reef Disappearing. Fishing with cyanide http://www.eniscuola.net/en/argomento/coral-reef/coral-reefs-disappearing/fishing-with-cyanide/   Accessed online July 1st 2018

Teh et al., 2013. A Global Estimate of the number of coral reef fishers. PLos One http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065397 Accessed online July 1st 2018


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