Parrotfish & Their Role in Marine Ecosystems


After visiting Barbados (a small island in the Caribbean) every December for 7 years. Each year I, unfortunately, saw a massive decline in the number of parrotfish on my daily snorkels and the reef slowly dying. By the 7th visit, I saw no parrotfish on shallow reefs on the East coast, apart from in the Folkestone Marine Protected Area.


When I spoke to the fishermen who let me take the below photo in December 2014, he didn't realise that removing so many parrotfish could affect the reefs on which he largely relies on economically, for tourism - (he was a snorkel guide). Therefore, I believe that the decline I was seeing in these amazing fish was most likely from overfishing and lack of education - it was right in front of my eyes, and he wasn’t the only one with a bundle of parrotfish in the 3 weeks I visited that beach...



However, there is some good news to my story…


Where the Barbados Marine Reserve was introduced a little further down from where these were caught, many different coloured parrotfish can be found in numerous sizes grazing on a healthy reef.


This proves that these fish need protection and where there are parrotfish there are healthier coral reefs.


 

Introducing the Parrotfish


There are around 60+ known species of parrotfish that live in our ocean’s reefs, which have a lifespan of around 5-7 years, and can grow up to an impressive 122 cm in length.


Parrotfish are extremely colourful tropical fish that spend around 90% of their day eating macroalgae (seaweed) found on corals. This pretty constant algae-eating mission is a natural process that helps clean and maintain a healthy reef.


To bite off the algae, parrotfish have very strong teeth, in fact, roughly 1,000 of them all lined up in 15 rows and fused together to form a beak-like structure, they almost look like a bad set of dentures! Their teeth are made from fluorapatite (consisting of calcium, fluorine, phosphorus, and oxygen) - the second strongest biomineral in the world!


When the parrotfish have worn out their teeth they fall to the ocean floor and break down into tiny coral bits which create the white sandy beaches that many people love to see. This is known as bioerosion - the process of breaking down hard substrates.


Parrotfish, unfortunately, face many threats such as climate change, marine pollution, invasive species (like lionfish), and overfishing.


Without these ‘algae-eating powerhouses’, corals would die from the suffocation of seaweeds, which has been seen in the South Pacific due to the overfishing of the Green Humphead/Bumphead Parrotfish (Bolbometopon muricatum).


In many countries, parrotfish are also seen as a delicacy and their meat is often falsely sold overseas as groupers, because of their higher demand, putting the poor parrotfish in more danger.



 

Parrotfish & Marine Ecosystems



Controlling Algal Communities

As mentioned, parrotfish are known for removing algae from corals around the world.


Their tightly-packed teeth stretch from their throat to the tip of their mouth to form a point, which gives them access to difficult crevices within the reef. This is one of the many reasons they are irreplaceable organisms in the ocean.


Sand Builders & Distributors

The Green Humphead Parrotfish is pretty special. These giant fish are responsible for most of the sand distribution in the coral reef biome. Their ability to grind coralline algae comes from their strong pharyngeal (throat) teeth. After grinding the algae, the Humphead Parrotfish digests it, excretes it (as poop), and then distributes it on the seafloor.



The tiny sand particles that parrotfish generate, help control algae populations and create the perfect surface for corals to attach and grow on. It is estimated that the Heavybeak Parrotfish (Chlorurus gibbus) can poop more than 900 kg of sand every year, compared to a regular parrotfish that excretes 363 kg of sand in its lifetime.


So, if there is a more sustainable fish to offer, take that over eating a parrotfish. Every time you eat a parrotfish, you are technically taking away 363 kg of sand from the ocean.



Coral Reef Colonies

The size and density of coral reef colonies are directly affected by parrotfish.


Ocean scientists from the University of California San Diego found that when more algae-eating fish such as parrotfish are on a reef, it grows faster. The more parrotfish graze on reefs, the clearer they are of seaweeds. However, if a parrotfish were to continuously bite the same patch of coral (known as focused biting), the coral may become damaged and large areas of coral tissue may be removed.


Saying that most parrotfish perform “spot biting”, which is beneficial to the coral reef ecosystem. The parrotfish only make individual bites on the coral, which are evenly distributed, and the seaweed is removed allowing the coral to respire.


 

Protecting Parrotfish


In the Caribbean, it is estimated that 70% of parrotfish have been overexploited and the likelihood of seeing a large adult parrotfish is very rare.


Unfortunately, some parrotfish make it too easy to be caught. For example, in the South Pacific, Bumphead Parrotfish have a habit of sleeping in groups at predictable locations in shallow water, which means many can easily be scooped up in large nets or speared by fishermen all at once.


In 2014, the IUCN recommended that parrotfish be legally protected from fisheries, enforcing fishing restrictions and educating the public on the ecological and economic importance of parrotfish.


In the Northern Gulf of Mexico, the Flower Garden Banks have been protected. This protection prohibits fish traps and parrotfish fishing.


In Bermuda, they also ban fish traps and spearfishing.


Bonaire, which is heavily reliant on tourism for income, has restricted fishing to improve the health of their reefs.


Despite these several campaigns, many Caribbean countries still do not actively protect parrotfish, which results in unprotected coral reefs and excessive algae growth.


If we do not protect parrotfish now, we will see more localised extinctions and eventually global extinctions of these fantastic tropical fish.


So, what can you do?


You can follow the #PassOnParrotfish which is a collaborative campaign launched by TNC (The Nature Conservancy) and partners in the Caribbean to raise awareness about the need to protect parrotfish to keep coral reefs healthy and thriving. Their aim is to use social media and other outreach tools, to encourage fishers, restaurants and consumers not to catch, sell or eat parrotfish because of the important role they play in maintaining coral reef health.


Donate to the WWF Reef Rescue Appeal.


Order some epic parrotfish printed products from Waterlust. "10% of profits from any purchase of Parrotfish Protection gear will be donated to Reef Relief to improve and protect our coral reef ecosystem through education, advocacy, and grassroots community efforts".

 



Written by Darby Bonner










 

References


Bonaldo, Roberta Martini (2010) The ecosystem role of parrotfishes on coral reefs. PhD thesis, James Cook University.


Bonaldo, Roberta & Hoey, Andrew & Bellwood, David. (2014). The Ecosystem Roles of Parrotfishes on Tropical Reefs. Oceanography and marine biology. 52. 81-132. 10.1201/b17143-3.


University of California - San Diego. (2017, January 23). Parrotfish are critical to coral reef health, study finds: Analysis reveals pivotal role of algae-eating fish in coral growth. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2017/01/170123094552.htm


https://www.nature.org/content/dam/tnc/nature/en/documents/TNC-Caribbean-CMBP-ParrotfishMagazine.pdf


https://www.nature.org/en-us/get-involved/how-to-help/animals-we-protect/parrotfish/


https://blog.nature.org/science/2017/12/29/fantastic-fecal-phenomena-of-the-animal-world/


https://ocean.si.edu/ocean-life/fish/tough-teeth-and-parrotfish-poop


https://newsday.co.tt/2021/01/07/protecting-the-parrotfish/

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