How Being a Picky Eater is Affecting Our Health: the Orange Spotted Filefish

Author: Brianna Delgado

Have you ever been lucky enough to catch a glimpse of an Oxymonacanthus longirostris, otherwise known as the orange-spotted filefish? More importantly, will you ever have this fortune? The orange-spotted filefish is a small and gorgeous light turquoise fish with vibrant orange spots. This unique looking fish is also known as the longnose filefish because its face ends with an elongated thin mouth, which almost looks like a yellow pipe cleaner! This fish lives amongst the shallow coral reefs in the Indo-Pacific Oceans (1). The filefish depends heavily on having a healthy home environment, because it doesn’t just live in the coral reefs it feeds there too! The filefish is on a strict coral diet and feeds on the polyps of the corals. Sadly, due to coral bleaching events this beautiful animal may go hungry, habitat-less, or even disappear altogether.

What is coral bleaching and why does it happen?

Coral bleaching is what occurs when healthy corals experience stress due to changes in their environment (2). This phenomenon gets its name from the color that the corals turn once they are bleached. What were once healthy, bright, and vibrant corals then turn into drab white corals. One change in environment that is known to stress corals out is a change in temperature. Climate change has contributed to a warming of our oceans, and as our oceans become warmer, our corals become more stressed. This is only one factor that is contributing to an increase in coral bleaching. You can read more about what changes may cause coral bleaching at the National Ocean Service's online ocean facts page(2).

So why can’t the orange-spotted filefish eat something else?

Essentially, the orange-spotted filefish is a very picky eater. It mostly feeds on the corals of the genus Acropora (3). Unfortunately, science has shown that acroporid corals are one of the most at risk corals for bleaching (3). Not only does the fish strictly feed on this type of coral, it has a preference as well. Think of it as loving ice cream, but only wanting to have the chocolate flavored ice cream. When not given their favorite ice cream flavor, the orange-spotted filefish doesn’t throw a tantrum, but its health declines instead. Research has shown that when the fish do not have their favorite flavor of coral available to them they tend to do poorly. Researchers conducted an experiment (4) to see how the orange-spotted filefish would respond when they were given their favorite flavor of coral versus when they were given their least favorite flavor of coral. The experiment showed that the fish that were given their least favorite flavor of coral experienced weight loss, a lower energy reserve, and didn’t reproduce during the time of the experiment. On the other hand, the fish that were given their favorite coral flavor had much better health and reproduced on 49% of the nights spent in the experiment. This study shows how important having healthy acroporid corals available to this species is for their reproductive success, growth, and energy levels. Scientists worry that without the fish’s favorite type of coral around the fish are at risk of going extinct.

In the late 90’s, researchers were able to identify the key differences in a population of orange-spotted filefish before and after a coral bleaching event occurred in 1998 (3). Their observations showed that many of the fish they observed disappeared, had much lower growth rates, and shortened their breeding season by a month (3). The researchers doing this study also observed that fish were increasing the size of their territories (3). This species eats within its own territory, so this means the fish were traveling further than usual in order to find food. It is likely that the fish were going further to find their favorite food because there was less available food in their usual territories due to coral bleaching. This is bad news for the filefish because not only is it hungry, but it’s using more energy in order to feel full. Can you imagine having to walk miles to different grocery stores in order to get each of the ingredients necessary for making your meal? I’m hungry just thinking about it.

Research has shown us how important it is for the survival of this species to have their favorite food. So, what can we do to help?

Coral reefs face many threats that can affect them directly in the water or indirectly, from far and wide. This being said, no matter how close or far you live from coral reefs you can take measures to prevent any direct or indirect harm to coral reefs and the species that depend on them. Here are a few practices you can incorporate into your own daily routine to protect our coral reefs, courtesy of the United States Environmental Protection Agency(5):

  • Recycle and dispose of trash properly.
  • Minimize use of fertilizers.
  • Use environmentally-friendly modes of transportation.
  • Reduce stormwater runoff.
  • Save energy at home and at work.
  • Be conscious when buying aquarium fish.
  • Spread the word! 

Collectively, we can make a difference to help ensure the beautiful orange-spotted filefish can always eat its favorite treat. Practicing daily activities such as recycling properly can minimize the amount of plastic debris that can find its way into our oceans. Using less fertilizers in our gardens can also lower the chances for harming the quality of water that later ends up in the ocean. These are a couple of examples of actions that can be taken to prevent indirect harm of coral reefs. Taking these preventative measures and pairing them with collaborative work within our communities can make a large impact. Together we can educate one another on this issue and find more solutions to help conserve this species and the biodiversity within our oceans.



  1. T. Kokita, A. Nakazono, Seasonal variation in the diel spawning time of the coral reef fish Oxymonacanthus longirostris (Monacanthidae): Parental control of progeny development. Mar. Ecol. Prog. Ser.199, 263–270 (2000).
  2. NOAA, What is coral bleaching? Natl. Ocean Atmos. Adminstration(2016).
  3. T. Kokita, A. Nakazono, Rapid response of an obligately corallivorous filefish Oxymonacanthus longirostris (Monacanthidae) to a mass coral bleaching event. Coral Reefs.20, 155–158 (2001).
  4. R. M. Brooker, G. P. Jones, P. L. Munday, Prey selectivity affects reproductive success of a corallivorous reef fish. Oecologia. 172, 409–416 (2013).
  5. EPA, What You Can Do to Help Protect Coral Reefs. United States Environ. Prot. Agency(2018).


Image Credits

Richard Ling, CC BY-SA 2.0, via Wikimedia Commons

Holobionics, CC BY-SA 4.0, via Wikimedia Commons

Acropora at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

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