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Terrifying Nemo - New Study on Impact of Boat Engine Noise on Fish Finds Clownfish Severely Bothered

9th April 2020
A clownfish and a passing motorboat overhead A clownfish and a passing motorboat overhead

Everyone who has ever seen the Pixar film Finding Nemo knows what a clownfish looks like, but a new study gives some alarming insight into their response to human behaviour.

A study by international scientists on the impact of motorboat engine noise found that clownfish are so bothered by it that they will hide, skip meals and even attack domino damselfish and other neighbours.

The erratic behaviour is the result of hormonal changes caused by the engine noise, the researchers from France, Chile and Britain state.

Working on the reefs around Moorea in French Polynesia, the scientists exposed 40 pairs of clownfish to recordings of natural reef sounds or motorboat noise for up to two days.

Vexing Nemo graphic illustration

The engine reverberations caused clownfish to “hide in the protective tentacles of their host anemone, move less into open water to feed, and to be more aggressive towards domino damselfish that also reside in the anemone”, they found.

They also found that anemonefish which were also affected by the noise were “unable to respond appropriately to a second stressor, putting them at greater risk from threats such as predators and climate change”.

The study found noise-exposed fish had elevated levels of the stress hormone, cortisol.

They also had higher levels of the reproductive hormones testosterone and 11-ketotestosterone, which corresponded with observed behavioural changes.

“These measurable hormones offer a window into complex behaviours and could be used to develop new noise-mitigation tools,” the scientists state.

Associate professor Suzanne Mills at the École Pratique des Hautes Études (EPHE) PSL Université Paris in France, who is lead author, noted that the high cortisol levels after two days of exposure suggest that clownfish become “chronically stressed by motorboat noise”.

“This compromises the stress response system, leaving clownfish unable to mount appropriate responses to further stressful events. If these stressful events include a predator, motorboat noise could have grave implications,” she said.

“Our new findings highlight the need to control man-made noise in marine protected habitats,” she said.

The paper, entitled Hormonal and behavioural effects of motorboat noise on wild coral reef fish, is published in the journal Environmental Pollution.

Lorna Siggins

About The Author

Lorna Siggins

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Lorna Siggins is a print and radio reporter, and a former Irish Times western correspondent. She is the author of Everest Callling (1994) on the first Irish Everest expedition; Mayday! Mayday! (2004) on Irish helicopter search and rescue; and Once Upon a Time in the West: the Corrib gas controversy (2010).

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Marine Science Perhaps it is the work of the Irish research vessel RV Celtic Explorer out in the Atlantic Ocean that best highlights the essential nature of marine research, development and sustainable management, through which Ireland is developing a strong and well-deserved reputation as an emerging centre of excellence. From Wavebob Ocean energy technology to aquaculture to weather buoys and oil exploration these pages document the work of Irish marine science and how Irish scientists have secured prominent roles in many European and international marine science bodies.

 

At A Glance – Ocean Facts

  • 71% of the earth’s surface is covered by the ocean
  • The ocean is responsible for the water cycle, which affects our weather
  • The ocean absorbs 30% of the carbon dioxide added to the atmosphere by human activity
  • The real map of Ireland has a seabed territory ten times the size of its land area
  • The ocean is the support system of our planet.
  • Over half of the oxygen we breathe was produced in the ocean
  • The global market for seaweed is valued at approximately €5.4 billion
  • · Coral reefs are among the oldest ecosystems in the world — at 230 million years
  • 1.9 million people live within 5km of the coast in Ireland
  • Ocean waters hold nearly 20 million tons of gold. If we could mine all of the gold from the ocean, we would have enough to give every person on earth 9lbs of the precious metal!
  • Aquaculture is the fastest growing food sector in the world – Ireland is ranked 7th largest aquaculture producer in the EU
  • The Atlantic Ocean is the second largest ocean in the world, covering 20% of the earth’s surface. Out of all the oceans, the Atlantic Ocean is the saltiest
  • The Pacific Ocean is the largest ocean in the world. It’s bigger than all the continents put together
  • Ireland is surrounded by some of the most productive fishing grounds in Europe, with Irish commercial fish landings worth around €200 million annually
  • 97% of the earth’s water is in the ocean
  • The ocean provides the greatest amount of the world’s protein consumed by humans
  • Plastic affects 700 species in the oceans from plankton to whales.
  • Only 10% of the oceans have been explored.
  • 8 million tonnes of plastic enter the ocean each year, equal to dumping a garbage truck of plastic into the ocean every minute.
  • 12 humans have walked on the moon but only 3 humans have been to the deepest part of the ocean.

(Ref: Marine Institute)

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